std: Move sys_common to libstd/sys_common

Make the directory structure reflect the module structure. I've always
found the existing structure confusing.

18 files changed, 3928 insertions, 0 deletions

diff --git a/src/libstd/sys_common/at_exit_imp.rs b/src/libstd/sys_common/at_exit_imp.rs
new file mode 100644
index 00000000000..ce6fd4cb075
--- /dev/null
+++ b/src/libstd/sys_common/at_exit_imp.rs
@@ -0,0 +1,80 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Implementation of running at_exit routines
+//!
+//! Documentation can be found on the `rt::at_exit` function.
+
+use alloc::boxed::FnBox;
+use ptr;
+use sys_common::mutex::Mutex;
+
+type Queue = Vec<Box<FnBox()>>;
+
+// NB these are specifically not types from `std::sync` as they currently rely
+// on poisoning and this module needs to operate at a lower level than requiring
+// the thread infrastructure to be in place (useful on the borders of
+// initialization/destruction).
+static LOCK: Mutex = Mutex::new();
+static mut QUEUE: *mut Queue = ptr::null_mut();
+
+// The maximum number of times the cleanup routines will be run. While running
+// the at_exit closures new ones may be registered, and this count is the number
+// of times the new closures will be allowed to register successfully. After
+// this number of iterations all new registrations will return `false`.
+const ITERS: usize = 10;
+
+unsafe fn init() -> bool {
+    if QUEUE.is_null() {
+        let state: Box<Queue> = box Vec::new();
+        QUEUE = Box::into_raw(state);
+    } else if QUEUE as usize == 1 {
+        // can't re-init after a cleanup
+        return false
+    }
+
+    true
+}
+
+pub fn cleanup() {
+    for i in 0..ITERS {
+        unsafe {
+            LOCK.lock();
+            let queue = QUEUE;
+            QUEUE = if i == ITERS - 1 {1} else {0} as *mut _;
+            LOCK.unlock();
+
+            // make sure we're not recursively cleaning up
+            assert!(queue as usize != 1);
+
+            // If we never called init, not need to cleanup!
+            if queue as usize != 0 {
+                let queue: Box<Queue> = Box::from_raw(queue);
+                for to_run in *queue {
+                    to_run();
+                }
+            }
+        }
+    }
+}
+
+pub fn push(f: Box<FnBox()>) -> bool {
+    let mut ret = true;
+    unsafe {
+        LOCK.lock();
+        if init() {
+            (*QUEUE).push(f);
+        } else {
+            ret = false;
+        }
+        LOCK.unlock();
+    }
+    ret
+}
diff --git a/src/libstd/sys_common/backtrace.rs b/src/libstd/sys_common/backtrace.rs
new file mode 100644
index 00000000000..a8540fed928
--- /dev/null
+++ b/src/libstd/sys_common/backtrace.rs
@@ -0,0 +1,257 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![cfg_attr(target_os = "nacl", allow(dead_code))]
+
+use env;
+use io::prelude::*;
+use io;
+use libc;
+use str;
+use sync::atomic::{self, Ordering};
+
+pub use sys::backtrace::write;
+
+#[cfg(target_pointer_width = "64")]
+pub const HEX_WIDTH: usize = 18;
+
+#[cfg(target_pointer_width = "32")]
+pub const HEX_WIDTH: usize = 10;
+
+// For now logging is turned off by default, and this function checks to see
+// whether the magical environment variable is present to see if it's turned on.
+pub fn log_enabled() -> bool {
+    static ENABLED: atomic::AtomicIsize = atomic::AtomicIsize::new(0);
+    match ENABLED.load(Ordering::SeqCst) {
+        1 => return false,
+        2 => return true,
+        _ => {}
+    }
+
+    let val = match env::var_os("RUST_BACKTRACE") {
+        Some(x) => if &x == "0" { 1 } else { 2 },
+        None => 1,
+    };
+    ENABLED.store(val, Ordering::SeqCst);
+    val == 2
+}
+
+// These output functions should now be used everywhere to ensure consistency.
+pub fn output(w: &mut Write, idx: isize, addr: *mut libc::c_void,
+              s: Option<&[u8]>) -> io::Result<()> {
+    write!(w, "  {:2}: {:2$?} - ", idx, addr, HEX_WIDTH)?;
+    match s.and_then(|s| str::from_utf8(s).ok()) {
+        Some(string) => demangle(w, string)?,
+        None => write!(w, "<unknown>")?,
+    }
+    w.write_all(&['\n' as u8])
+}
+
+#[allow(dead_code)]
+pub fn output_fileline(w: &mut Write, file: &[u8], line: libc::c_int,
+                       more: bool) -> io::Result<()> {
+    let file = str::from_utf8(file).unwrap_or("<unknown>");
+    // prior line: "  ##: {:2$} - func"
+    write!(w, "      {:3$}at {}:{}", "", file, line, HEX_WIDTH)?;
+    if more {
+        write!(w, " <... and possibly more>")?;
+    }
+    w.write_all(&['\n' as u8])
+}
+
+
+// All rust symbols are in theory lists of "::"-separated identifiers. Some
+// assemblers, however, can't handle these characters in symbol names. To get
+// around this, we use C++-style mangling. The mangling method is:
+//
+// 1. Prefix the symbol with "_ZN"
+// 2. For each element of the path, emit the length plus the element
+// 3. End the path with "E"
+//
+// For example, "_ZN4testE" => "test" and "_ZN3foo3barE" => "foo::bar".
+//
+// We're the ones printing our backtraces, so we can't rely on anything else to
+// demangle our symbols. It's *much* nicer to look at demangled symbols, so
+// this function is implemented to give us nice pretty output.
+//
+// Note that this demangler isn't quite as fancy as it could be. We have lots
+// of other information in our symbols like hashes, version, type information,
+// etc. Additionally, this doesn't handle glue symbols at all.
+pub fn demangle(writer: &mut Write, s: &str) -> io::Result<()> {
+    // First validate the symbol. If it doesn't look like anything we're
+    // expecting, we just print it literally. Note that we must handle non-rust
+    // symbols because we could have any function in the backtrace.
+    let mut valid = true;
+    let mut inner = s;
+    if s.len() > 4 && s.starts_with("_ZN") && s.ends_with("E") {
+        inner = &s[3 .. s.len() - 1];
+    // On Windows, dbghelp strips leading underscores, so we accept "ZN...E" form too.
+    } else if s.len() > 3 && s.starts_with("ZN") && s.ends_with("E") {
+        inner = &s[2 .. s.len() - 1];
+    } else {
+        valid = false;
+    }
+
+    if valid {
+        let mut chars = inner.chars();
+        while valid {
+            let mut i = 0;
+            for c in chars.by_ref() {
+                if c.is_numeric() {
+                    i = i * 10 + c as usize - '0' as usize;
+                } else {
+                    break
+                }
+            }
+            if i == 0 {
+                valid = chars.next().is_none();
+                break
+            } else if chars.by_ref().take(i - 1).count() != i - 1 {
+                valid = false;
+            }
+        }
+    }
+
+    // Alright, let's do this.
+    if !valid {
+        writer.write_all(s.as_bytes())?;
+    } else {
+        let mut first = true;
+        while !inner.is_empty() {
+            if !first {
+                writer.write_all(b"::")?;
+            } else {
+                first = false;
+            }
+            let mut rest = inner;
+            while rest.chars().next().unwrap().is_numeric() {
+                rest = &rest[1..];
+            }
+            let i: usize = inner[.. (inner.len() - rest.len())].parse().unwrap();
+            inner = &rest[i..];
+            rest = &rest[..i];
+            if rest.starts_with("_$") {
+                rest = &rest[1..];
+            }
+            while !rest.is_empty() {
+                if rest.starts_with(".") {
+                    if let Some('.') = rest[1..].chars().next() {
+                        writer.write_all(b"::")?;
+                        rest = &rest[2..];
+                    } else {
+                        writer.write_all(b".")?;
+                        rest = &rest[1..];
+                    }
+                } else if rest.starts_with("$") {
+                    macro_rules! demangle {
+                        ($($pat:expr => $demangled:expr),*) => ({
+                            $(if rest.starts_with($pat) {
+                                writer.write_all($demangled)?;
+                                rest = &rest[$pat.len()..];
+                              } else)*
+                            {
+                                writer.write_all(rest.as_bytes())?;
+                                break;
+                            }
+
+                        })
+                    }
+
+                    // see src/librustc/back/link.rs for these mappings
+                    demangle! (
+                        "$SP$" => b"@",
+                        "$BP$" => b"*",
+                        "$RF$" => b"&",
+                        "$LT$" => b"<",
+                        "$GT$" => b">",
+                        "$LP$" => b"(",
+                        "$RP$" => b")",
+                        "$C$" => b",",
+
+                        // in theory we can demangle any Unicode code point, but
+                        // for simplicity we just catch the common ones.
+                        "$u7e$" => b"~",
+                        "$u20$" => b" ",
+                        "$u27$" => b"'",
+                        "$u5b$" => b"[",
+                        "$u5d$" => b"]",
+                        "$u7b$" => b"{",
+                        "$u7d$" => b"}",
+                        "$u3b$" => b";",
+                        "$u2b$" => b"+",
+                        "$u22$" => b"\""
+                    )
+                } else {
+                    let idx = match rest.char_indices().find(|&(_, c)| c == '$' || c == '.') {
+                        None => rest.len(),
+                        Some((i, _)) => i,
+                    };
+                    writer.write_all(rest[..idx].as_bytes())?;
+                    rest = &rest[idx..];
+                }
+            }
+        }
+    }
+
+    Ok(())
+}
+
+#[cfg(test)]
+mod tests {
+    use sys_common;
+    macro_rules! t { ($a:expr, $b:expr) => ({
+        let mut m = Vec::new();
+        sys_common::backtrace::demangle(&mut m, $a).unwrap();
+        assert_eq!(String::from_utf8(m).unwrap(), $b);
+    }) }
+
+    #[test]
+    fn demangle() {
+        t!("test", "test");
+        t!("_ZN4testE", "test");
+        t!("_ZN4test", "_ZN4test");
+        t!("_ZN4test1a2bcE", "test::a::bc");
+    }
+
+    #[test]
+    fn demangle_dollars() {
+        t!("_ZN4$RP$E", ")");
+        t!("_ZN8$RF$testE", "&test");
+        t!("_ZN8$BP$test4foobE", "*test::foob");
+        t!("_ZN9$u20$test4foobE", " test::foob");
+        t!("_ZN35Bar$LT$$u5b$u32$u3b$$u20$4$u5d$$GT$E", "Bar<[u32; 4]>");
+    }
+
+    #[test]
+    fn demangle_many_dollars() {
+        t!("_ZN13test$u20$test4foobE", "test test::foob");
+        t!("_ZN12test$BP$test4foobE", "test*test::foob");
+    }
+
+    #[test]
+    fn demangle_windows() {
+        t!("ZN4testE", "test");
+        t!("ZN13test$u20$test4foobE", "test test::foob");
+        t!("ZN12test$RF$test4foobE", "test&test::foob");
+    }
+
+    #[test]
+    fn demangle_elements_beginning_with_underscore() {
+        t!("_ZN13_$LT$test$GT$E", "<test>");
+        t!("_ZN28_$u7b$$u7b$closure$u7d$$u7d$E", "{{closure}}");
+        t!("_ZN15__STATIC_FMTSTRE", "__STATIC_FMTSTR");
+    }
+
+    #[test]
+    fn demangle_trait_impls() {
+        t!("_ZN71_$LT$Test$u20$$u2b$$u20$$u27$static$u20$as$u20$foo..Bar$LT$Test$GT$$GT$3barE",
+           "<Test + 'static as foo::Bar<Test>>::bar");
+    }
+}
diff --git a/src/libstd/sys_common/condvar.rs b/src/libstd/sys_common/condvar.rs
new file mode 100644
index 00000000000..b6f29dd5fc3
--- /dev/null
+++ b/src/libstd/sys_common/condvar.rs
@@ -0,0 +1,70 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use time::Duration;
+use sys_common::mutex::{self, Mutex};
+use sys::condvar as imp;
+
+/// An OS-based condition variable.
+///
+/// This structure is the lowest layer possible on top of the OS-provided
+/// condition variables. It is consequently entirely unsafe to use. It is
+/// recommended to use the safer types at the top level of this crate instead of
+/// this type.
+pub struct Condvar(imp::Condvar);
+
+impl Condvar {
+    /// Creates a new condition variable for use.
+    ///
+    /// Behavior is undefined if the condition variable is moved after it is
+    /// first used with any of the functions below.
+    pub const fn new() -> Condvar { Condvar(imp::Condvar::new()) }
+
+    /// Prepares the condition variable for use.
+    ///
+    /// This should be called once the condition variable is at a stable memory
+    /// address.
+    #[inline]
+    pub unsafe fn init(&mut self) { self.0.init() }
+
+    /// Signals one waiter on this condition variable to wake up.
+    #[inline]
+    pub unsafe fn notify_one(&self) { self.0.notify_one() }
+
+    /// Awakens all current waiters on this condition variable.
+    #[inline]
+    pub unsafe fn notify_all(&self) { self.0.notify_all() }
+
+    /// Waits for a signal on the specified mutex.
+    ///
+    /// Behavior is undefined if the mutex is not locked by the current thread.
+    /// Behavior is also undefined if more than one mutex is used concurrently
+    /// on this condition variable.
+    #[inline]
+    pub unsafe fn wait(&self, mutex: &Mutex) { self.0.wait(mutex::raw(mutex)) }
+
+    /// Waits for a signal on the specified mutex with a timeout duration
+    /// specified by `dur` (a relative time into the future).
+    ///
+    /// Behavior is undefined if the mutex is not locked by the current thread.
+    /// Behavior is also undefined if more than one mutex is used concurrently
+    /// on this condition variable.
+    #[inline]
+    pub unsafe fn wait_timeout(&self, mutex: &Mutex, dur: Duration) -> bool {
+        self.0.wait_timeout(mutex::raw(mutex), dur)
+    }
+
+    /// Deallocates all resources associated with this condition variable.
+    ///
+    /// Behavior is undefined if there are current or will be future users of
+    /// this condition variable.
+    #[inline]
+    pub unsafe fn destroy(&self) { self.0.destroy() }
+}
diff --git a/src/libstd/sys_common/gnu/libbacktrace.rs b/src/libstd/sys_common/gnu/libbacktrace.rs
new file mode 100644
index 00000000000..b5802afc109
--- /dev/null
+++ b/src/libstd/sys_common/gnu/libbacktrace.rs
@@ -0,0 +1,181 @@
+// Copyright 2014-2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use io;
+use io::prelude::*;
+use libc;
+use sys_common::backtrace::{output, output_fileline};
+
+pub fn print(w: &mut Write, idx: isize, addr: *mut libc::c_void,
+             symaddr: *mut libc::c_void) -> io::Result<()> {
+    use ffi::CStr;
+    use ptr;
+
+    ////////////////////////////////////////////////////////////////////////
+    // libbacktrace.h API
+    ////////////////////////////////////////////////////////////////////////
+    type backtrace_syminfo_callback =
+        extern "C" fn(data: *mut libc::c_void,
+                      pc: libc::uintptr_t,
+                      symname: *const libc::c_char,
+                      symval: libc::uintptr_t,
+                      symsize: libc::uintptr_t);
+    type backtrace_full_callback =
+        extern "C" fn(data: *mut libc::c_void,
+                      pc: libc::uintptr_t,
+                      filename: *const libc::c_char,
+                      lineno: libc::c_int,
+                      function: *const libc::c_char) -> libc::c_int;
+    type backtrace_error_callback =
+        extern "C" fn(data: *mut libc::c_void,
+                      msg: *const libc::c_char,
+                      errnum: libc::c_int);
+    enum backtrace_state {}
+    #[link(name = "backtrace", kind = "static")]
+    #[cfg(all(not(test), not(cargobuild)))]
+    extern {}
+
+    extern {
+        fn backtrace_create_state(filename: *const libc::c_char,
+                                  threaded: libc::c_int,
+                                  error: backtrace_error_callback,
+                                  data: *mut libc::c_void)
+                                  -> *mut backtrace_state;
+        fn backtrace_syminfo(state: *mut backtrace_state,
+                             addr: libc::uintptr_t,
+                             cb: backtrace_syminfo_callback,
+                             error: backtrace_error_callback,
+                             data: *mut libc::c_void) -> libc::c_int;
+        fn backtrace_pcinfo(state: *mut backtrace_state,
+                            addr: libc::uintptr_t,
+                            cb: backtrace_full_callback,
+                            error: backtrace_error_callback,
+                            data: *mut libc::c_void) -> libc::c_int;
+    }
+
+    ////////////////////////////////////////////////////////////////////////
+    // helper callbacks
+    ////////////////////////////////////////////////////////////////////////
+
+    type FileLine = (*const libc::c_char, libc::c_int);
+
+    extern fn error_cb(_data: *mut libc::c_void, _msg: *const libc::c_char,
+                       _errnum: libc::c_int) {
+        // do nothing for now
+    }
+    extern fn syminfo_cb(data: *mut libc::c_void,
+                         _pc: libc::uintptr_t,
+                         symname: *const libc::c_char,
+                         _symval: libc::uintptr_t,
+                         _symsize: libc::uintptr_t) {
+        let slot = data as *mut *const libc::c_char;
+        unsafe { *slot = symname; }
+    }
+    extern fn pcinfo_cb(data: *mut libc::c_void,
+                        _pc: libc::uintptr_t,
+                        filename: *const libc::c_char,
+                        lineno: libc::c_int,
+                        _function: *const libc::c_char) -> libc::c_int {
+        if !filename.is_null() {
+            let slot = data as *mut &mut [FileLine];
+            let buffer = unsafe {ptr::read(slot)};
+
+            // if the buffer is not full, add file:line to the buffer
+            // and adjust the buffer for next possible calls to pcinfo_cb.
+            if !buffer.is_empty() {
+                buffer[0] = (filename, lineno);
+                unsafe { ptr::write(slot, &mut buffer[1..]); }
+            }
+        }
+
+        0
+    }
+
+    // The libbacktrace API supports creating a state, but it does not
+    // support destroying a state. I personally take this to mean that a
+    // state is meant to be created and then live forever.
+    //
+    // I would love to register an at_exit() handler which cleans up this
+    // state, but libbacktrace provides no way to do so.
+    //
+    // With these constraints, this function has a statically cached state
+    // that is calculated the first time this is requested. Remember that
+    // backtracing all happens serially (one global lock).
+    //
+    // Things don't work so well on not-Linux since libbacktrace can't track
+    // down that executable this is. We at one point used env::current_exe but
+    // it turns out that there are some serious security issues with that
+    // approach.
+    //
+    // Specifically, on certain platforms like BSDs, a malicious actor can cause
+    // an arbitrary file to be placed at the path returned by current_exe.
+    // libbacktrace does not behave defensively in the presence of ill-formed
+    // DWARF information, and has been demonstrated to segfault in at least one
+    // case. There is no evidence at the moment to suggest that a more carefully
+    // constructed file can't cause arbitrary code execution. As a result of all
+    // of this, we don't hint libbacktrace with the path to the current process.
+    unsafe fn init_state() -> *mut backtrace_state {
+        static mut STATE: *mut backtrace_state = ptr::null_mut();
+        if !STATE.is_null() { return STATE }
+        STATE = backtrace_create_state(ptr::null(), 0, error_cb,
+                                       ptr::null_mut());
+        STATE
+    }
+
+    ////////////////////////////////////////////////////////////////////////
+    // translation
+    ////////////////////////////////////////////////////////////////////////
+
+    // backtrace errors are currently swept under the rug, only I/O
+    // errors are reported
+    let state = unsafe { init_state() };
+    if state.is_null() {
+        return output(w, idx, addr, None)
+    }
+    let mut data = ptr::null();
+    let data_addr = &mut data as *mut *const libc::c_char;
+    let ret = unsafe {
+        backtrace_syminfo(state, symaddr as libc::uintptr_t,
+                          syminfo_cb, error_cb,
+                          data_addr as *mut libc::c_void)
+    };
+    if ret == 0 || data.is_null() {
+        output(w, idx, addr, None)?;
+    } else {
+        output(w, idx, addr, Some(unsafe { CStr::from_ptr(data).to_bytes() }))?;
+    }
+
+    // pcinfo may return an arbitrary number of file:line pairs,
+    // in the order of stack trace (i.e. inlined calls first).
+    // in order to avoid allocation, we stack-allocate a fixed size of entries.
+    const FILELINE_SIZE: usize = 32;
+    let mut fileline_buf = [(ptr::null(), -1); FILELINE_SIZE];
+    let ret;
+    let fileline_count;
+    {
+        let mut fileline_win: &mut [FileLine] = &mut fileline_buf;
+        let fileline_addr = &mut fileline_win as *mut &mut [FileLine];
+        ret = unsafe {
+            backtrace_pcinfo(state, addr as libc::uintptr_t,
+                             pcinfo_cb, error_cb,
+                             fileline_addr as *mut libc::c_void)
+        };
+        fileline_count = FILELINE_SIZE - fileline_win.len();
+    }
+    if ret == 0 {
+        for (i, &(file, line)) in fileline_buf[..fileline_count].iter().enumerate() {
+            if file.is_null() { continue; } // just to be sure
+            let file = unsafe { CStr::from_ptr(file).to_bytes() };
+            output_fileline(w, file, line, i == FILELINE_SIZE - 1)?;
+        }
+    }
+
+    Ok(())
+}
diff --git a/src/libstd/sys_common/gnu/mod.rs b/src/libstd/sys_common/gnu/mod.rs
new file mode 100644
index 00000000000..3a8cf2d8425
--- /dev/null
+++ b/src/libstd/sys_common/gnu/mod.rs
@@ -0,0 +1,15 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![allow(missing_docs)]
+#![allow(non_camel_case_types)]
+#![allow(non_snake_case)]
+
+pub mod libbacktrace;
diff --git a/src/libstd/sys_common/io.rs b/src/libstd/sys_common/io.rs
new file mode 100644
index 00000000000..23daeeb5187
--- /dev/null
+++ b/src/libstd/sys_common/io.rs
@@ -0,0 +1,179 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+use io;
+use io::ErrorKind;
+use io::Read;
+use slice::from_raw_parts_mut;
+
+pub const DEFAULT_BUF_SIZE: usize = 8 * 1024;
+
+// Provides read_to_end functionality over an uninitialized buffer.
+// This function is unsafe because it calls the underlying
+// read function with a slice into uninitialized memory. The default
+// implementation of read_to_end for readers will zero out new memory in
+// the buf before passing it to read, but avoiding this zero can often
+// lead to a fairly significant performance win.
+//
+// Implementations using this method have to adhere to two guarantees:
+//  *  The implementation of read never reads the buffer provided.
+//  *  The implementation of read correctly reports how many bytes were written.
+pub unsafe fn read_to_end_uninitialized(r: &mut Read, buf: &mut Vec<u8>) -> io::Result<usize> {
+
+    let start_len = buf.len();
+    buf.reserve(16);
+
+    // Always try to read into the empty space of the vector (from the length to the capacity).
+    // If the vector ever fills up then we reserve an extra byte which should trigger the normal
+    // reallocation routines for the vector, which will likely double the size.
+    //
+    // This function is similar to the read_to_end function in std::io, but the logic about
+    // reservations and slicing is different enough that this is duplicated here.
+    loop {
+        if buf.len() == buf.capacity() {
+            buf.reserve(1);
+        }
+
+        let buf_slice = from_raw_parts_mut(buf.as_mut_ptr().offset(buf.len() as isize),
+                                           buf.capacity() - buf.len());
+
+        match r.read(buf_slice) {
+            Ok(0) => { return Ok(buf.len() - start_len); }
+            Ok(n) => { let len = buf.len() + n; buf.set_len(len); },
+            Err(ref e) if e.kind() == ErrorKind::Interrupted => { }
+            Err(e) => { return Err(e); }
+        }
+    }
+}
+
+#[cfg(test)]
+#[allow(dead_code)] // not used on emscripten
+pub mod test {
+    use path::{Path, PathBuf};
+    use env;
+    use rand::{self, Rng};
+    use fs;
+
+    pub struct TempDir(PathBuf);
+
+    impl TempDir {
+        pub fn join(&self, path: &str) -> PathBuf {
+            let TempDir(ref p) = *self;
+            p.join(path)
+        }
+
+        pub fn path<'a>(&'a self) -> &'a Path {
+            let TempDir(ref p) = *self;
+            p
+        }
+    }
+
+    impl Drop for TempDir {
+        fn drop(&mut self) {
+            // Gee, seeing how we're testing the fs module I sure hope that we
+            // at least implement this correctly!
+            let TempDir(ref p) = *self;
+            fs::remove_dir_all(p).unwrap();
+        }
+    }
+
+    pub fn tmpdir() -> TempDir {
+        let p = env::temp_dir();
+        let mut r = rand::thread_rng();
+        let ret = p.join(&format!("rust-{}", r.next_u32()));
+        fs::create_dir(&ret).unwrap();
+        TempDir(ret)
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use io::prelude::*;
+    use super::*;
+    use io;
+    use io::{ErrorKind, Take, Repeat, repeat};
+    use slice::from_raw_parts;
+
+    struct ErrorRepeat {
+        lr: Take<Repeat>
+    }
+
+    fn error_repeat(byte: u8, limit: u64) -> ErrorRepeat {
+        ErrorRepeat { lr: repeat(byte).take(limit) }
+    }
+
+    impl Read for ErrorRepeat {
+        fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+            let ret = self.lr.read(buf);
+            if let Ok(0) = ret {
+                return Err(io::Error::new(ErrorKind::Other, ""))
+            }
+            ret
+        }
+    }
+
+    fn init_vec_data() -> Vec<u8> {
+        let mut vec = vec![10u8; 200];
+        unsafe { vec.set_len(0); }
+        vec
+    }
+
+    fn assert_all_eq(buf: &[u8], value: u8) {
+        for n in buf {
+            assert_eq!(*n, value);
+        }
+    }
+
+    fn validate(buf: &Vec<u8>, good_read_len: usize) {
+        assert_all_eq(buf, 1u8);
+        let cap = buf.capacity();
+        let end_slice = unsafe { from_raw_parts(buf.as_ptr().offset(good_read_len as isize),
+                                                    cap - good_read_len) };
+        assert_all_eq(end_slice, 10u8);
+    }
+
+    #[test]
+    fn read_to_end_uninit_error() {
+        let mut er = error_repeat(1,100);
+        let mut vec = init_vec_data();
+        if let Err(_) = unsafe { read_to_end_uninitialized(&mut er, &mut vec) } {
+            validate(&vec, 100);
+        } else {
+            assert!(false);
+        }
+    }
+
+    #[test]
+    fn read_to_end_uninit_zero_len_vec() {
+        let mut er = repeat(1).take(100);
+        let mut vec = Vec::new();
+        let n = unsafe{ read_to_end_uninitialized(&mut er, &mut vec).unwrap() };
+        assert_all_eq(&vec, 1u8);
+        assert_eq!(vec.len(), n);
+    }
+
+    #[test]
+    fn read_to_end_uninit_good() {
+        let mut er = repeat(1).take(100);
+        let mut vec = init_vec_data();
+        let n = unsafe{ read_to_end_uninitialized(&mut er, &mut vec).unwrap() };
+        validate(&vec, 100);
+        assert_eq!(vec.len(), n);
+    }
+
+    #[bench]
+    #[cfg_attr(target_os = "emscripten", ignore)]
+    fn bench_uninitialized(b: &mut ::test::Bencher) {
+        b.iter(|| {
+            let mut lr = repeat(1).take(10000000);
+            let mut vec = Vec::with_capacity(1024);
+            unsafe { read_to_end_uninitialized(&mut lr, &mut vec) }
+        });
+    }
+}
diff --git a/src/libstd/sys_common/memchr.rs b/src/libstd/sys_common/memchr.rs
new file mode 100644
index 00000000000..3824a5fb528
--- /dev/null
+++ b/src/libstd/sys_common/memchr.rs
@@ -0,0 +1,230 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+//
+// Original implementation taken from rust-memchr
+// Copyright 2015 Andrew Gallant, bluss and Nicolas Koch
+
+#[allow(dead_code)]
+pub mod fallback {
+    use cmp;
+    use mem;
+
+    const LO_U64: u64 = 0x0101010101010101;
+    const HI_U64: u64 = 0x8080808080808080;
+
+    // use truncation
+    const LO_USIZE: usize = LO_U64 as usize;
+    const HI_USIZE: usize = HI_U64 as usize;
+
+    /// Return `true` if `x` contains any zero byte.
+    ///
+    /// From *Matters Computational*, J. Arndt
+    ///
+    /// "The idea is to subtract one from each of the bytes and then look for
+    /// bytes where the borrow propagated all the way to the most significant
+    /// bit."
+    #[inline]
+    fn contains_zero_byte(x: usize) -> bool {
+        x.wrapping_sub(LO_USIZE) & !x & HI_USIZE != 0
+    }
+
+    #[cfg(target_pointer_width = "32")]
+    #[inline]
+    fn repeat_byte(b: u8) -> usize {
+        let mut rep = (b as usize) << 8 | b as usize;
+        rep = rep << 16 | rep;
+        rep
+    }
+
+    #[cfg(target_pointer_width = "64")]
+    #[inline]
+    fn repeat_byte(b: u8) -> usize {
+        let mut rep = (b as usize) << 8 | b as usize;
+        rep = rep << 16 | rep;
+        rep = rep << 32 | rep;
+        rep
+    }
+
+    /// Return the first index matching the byte `a` in `text`.
+    pub fn memchr(x: u8, text: &[u8]) -> Option<usize> {
+        // Scan for a single byte value by reading two `usize` words at a time.
+        //
+        // Split `text` in three parts
+        // - unaligned initial part, before the first word aligned address in text
+        // - body, scan by 2 words at a time
+        // - the last remaining part, < 2 word size
+        let len = text.len();
+        let ptr = text.as_ptr();
+        let usize_bytes = mem::size_of::<usize>();
+
+        // search up to an aligned boundary
+        let align = (ptr as usize) & (usize_bytes- 1);
+        let mut offset;
+        if align > 0 {
+            offset = cmp::min(usize_bytes - align, len);
+            if let Some(index) = text[..offset].iter().position(|elt| *elt == x) {
+                return Some(index);
+            }
+        } else {
+            offset = 0;
+        }
+
+        // search the body of the text
+        let repeated_x = repeat_byte(x);
+
+        if len >= 2 * usize_bytes {
+            while offset <= len - 2 * usize_bytes {
+                unsafe {
+                    let u = *(ptr.offset(offset as isize) as *const usize);
+                    let v = *(ptr.offset((offset + usize_bytes) as isize) as *const usize);
+
+                    // break if there is a matching byte
+                    let zu = contains_zero_byte(u ^ repeated_x);
+                    let zv = contains_zero_byte(v ^ repeated_x);
+                    if zu || zv {
+                        break;
+                    }
+                }
+                offset += usize_bytes * 2;
+            }
+        }
+
+        // find the byte after the point the body loop stopped
+        text[offset..].iter().position(|elt| *elt == x).map(|i| offset + i)
+    }
+
+    /// Return the last index matching the byte `a` in `text`.
+    pub fn memrchr(x: u8, text: &[u8]) -> Option<usize> {
+        // Scan for a single byte value by reading two `usize` words at a time.
+        //
+        // Split `text` in three parts
+        // - unaligned tail, after the last word aligned address in text
+        // - body, scan by 2 words at a time
+        // - the first remaining bytes, < 2 word size
+        let len = text.len();
+        let ptr = text.as_ptr();
+        let usize_bytes = mem::size_of::<usize>();
+
+        // search to an aligned boundary
+        let end_align = (ptr as usize + len) & (usize_bytes - 1);
+        let mut offset;
+        if end_align > 0 {
+            offset = if end_align >= len { 0 } else { len - end_align };
+            if let Some(index) = text[offset..].iter().rposition(|elt| *elt == x) {
+                return Some(offset + index);
+            }
+        } else {
+            offset = len;
+        }
+
+        // search the body of the text
+        let repeated_x = repeat_byte(x);
+
+        while offset >= 2 * usize_bytes {
+            unsafe {
+                let u = *(ptr.offset(offset as isize - 2 * usize_bytes as isize) as *const usize);
+                let v = *(ptr.offset(offset as isize - usize_bytes as isize) as *const usize);
+
+                // break if there is a matching byte
+                let zu = contains_zero_byte(u ^ repeated_x);
+                let zv = contains_zero_byte(v ^ repeated_x);
+                if zu || zv {
+                    break;
+                }
+            }
+            offset -= 2 * usize_bytes;
+        }
+
+        // find the byte before the point the body loop stopped
+        text[..offset].iter().rposition(|elt| *elt == x)
+    }
+
+    // test fallback implementations on all platforms
+    #[test]
+    fn matches_one() {
+        assert_eq!(Some(0), memchr(b'a', b"a"));
+    }
+
+    #[test]
+    fn matches_begin() {
+        assert_eq!(Some(0), memchr(b'a', b"aaaa"));
+    }
+
+    #[test]
+    fn matches_end() {
+        assert_eq!(Some(4), memchr(b'z', b"aaaaz"));
+    }
+
+    #[test]
+    fn matches_nul() {
+        assert_eq!(Some(4), memchr(b'\x00', b"aaaa\x00"));
+    }
+
+    #[test]
+    fn matches_past_nul() {
+        assert_eq!(Some(5), memchr(b'z', b"aaaa\x00z"));
+    }
+
+    #[test]
+    fn no_match_empty() {
+        assert_eq!(None, memchr(b'a', b""));
+    }
+
+    #[test]
+    fn no_match() {
+        assert_eq!(None, memchr(b'a', b"xyz"));
+    }
+
+    #[test]
+    fn matches_one_reversed() {
+        assert_eq!(Some(0), memrchr(b'a', b"a"));
+    }
+
+    #[test]
+    fn matches_begin_reversed() {
+        assert_eq!(Some(3), memrchr(b'a', b"aaaa"));
+    }
+
+    #[test]
+    fn matches_end_reversed() {
+        assert_eq!(Some(0), memrchr(b'z', b"zaaaa"));
+    }
+
+    #[test]
+    fn matches_nul_reversed() {
+        assert_eq!(Some(4), memrchr(b'\x00', b"aaaa\x00"));
+    }
+
+    #[test]
+    fn matches_past_nul_reversed() {
+        assert_eq!(Some(0), memrchr(b'z', b"z\x00aaaa"));
+    }
+
+    #[test]
+    fn no_match_empty_reversed() {
+        assert_eq!(None, memrchr(b'a', b""));
+    }
+
+    #[test]
+    fn no_match_reversed() {
+        assert_eq!(None, memrchr(b'a', b"xyz"));
+    }
+
+    #[test]
+    fn each_alignment_reversed() {
+        let mut data = [1u8; 64];
+        let needle = 2;
+        let pos = 40;
+        data[pos] = needle;
+        for start in 0..16 {
+            assert_eq!(Some(pos - start), memrchr(needle, &data[start..]));
+        }
+    }
+}
diff --git a/src/libstd/sys_common/mod.rs b/src/libstd/sys_common/mod.rs
new file mode 100644
index 00000000000..2845f895f18
--- /dev/null
+++ b/src/libstd/sys_common/mod.rs
@@ -0,0 +1,117 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![allow(missing_docs)]
+
+use sync::Once;
+use sys;
+
+macro_rules! rtabort {
+    ($($t:tt)*) => (::sys_common::util::abort(format_args!($($t)*)))
+}
+
+macro_rules! rtassert {
+    ($e:expr) => ({
+        if !$e {
+            rtabort!(concat!("assertion failed: ", stringify!($e)))
+        }
+    })
+}
+
+pub mod at_exit_imp;
+#[cfg(any(not(cargobuild), feature = "backtrace"))]
+pub mod backtrace;
+pub mod condvar;
+pub mod io;
+pub mod memchr;
+pub mod mutex;
+pub mod net;
+pub mod poison;
+pub mod remutex;
+pub mod rwlock;
+pub mod thread;
+pub mod thread_info;
+pub mod thread_local;
+pub mod util;
+pub mod wtf8;
+
+#[cfg(any(not(cargobuild), feature = "backtrace"))]
+#[cfg(any(all(unix, not(any(target_os = "macos", target_os = "ios", target_os = "emscripten"))),
+          all(windows, target_env = "gnu")))]
+pub mod gnu;
+
+// common error constructors
+
+/// A trait for viewing representations from std types
+#[doc(hidden)]
+pub trait AsInner<Inner: ?Sized> {
+    fn as_inner(&self) -> &Inner;
+}
+
+/// A trait for viewing representations from std types
+#[doc(hidden)]
+pub trait AsInnerMut<Inner: ?Sized> {
+    fn as_inner_mut(&mut self) -> &mut Inner;
+}
+
+/// A trait for extracting representations from std types
+#[doc(hidden)]
+pub trait IntoInner<Inner> {
+    fn into_inner(self) -> Inner;
+}
+
+/// A trait for creating std types from internal representations
+#[doc(hidden)]
+pub trait FromInner<Inner> {
+    fn from_inner(inner: Inner) -> Self;
+}
+
+/// Enqueues a procedure to run when the main thread exits.
+///
+/// Currently these closures are only run once the main *Rust* thread exits.
+/// Once the `at_exit` handlers begin running, more may be enqueued, but not
+/// infinitely so. Eventually a handler registration will be forced to fail.
+///
+/// Returns `Ok` if the handler was successfully registered, meaning that the
+/// closure will be run once the main thread exits. Returns `Err` to indicate
+/// that the closure could not be registered, meaning that it is not scheduled
+/// to be run.
+pub fn at_exit<F: FnOnce() + Send + 'static>(f: F) -> Result<(), ()> {
+    if at_exit_imp::push(Box::new(f)) {Ok(())} else {Err(())}
+}
+
+/// One-time runtime cleanup.
+pub fn cleanup() {
+    static CLEANUP: Once = Once::new();
+    CLEANUP.call_once(|| unsafe {
+        sys::args::cleanup();
+        sys::stack_overflow::cleanup();
+        at_exit_imp::cleanup();
+    });
+}
+
+// Computes (value*numer)/denom without overflow, as long as both
+// (numer*denom) and the overall result fit into i64 (which is the case
+// for our time conversions).
+#[allow(dead_code)] // not used on all platforms
+pub fn mul_div_u64(value: u64, numer: u64, denom: u64) -> u64 {
+    let q = value / denom;
+    let r = value % denom;
+    // Decompose value as (value/denom*denom + value%denom),
+    // substitute into (value*numer)/denom and simplify.
+    // r < denom, so (denom*numer) is the upper bound of (r*numer)
+    q * numer + r * numer / denom
+}
+
+#[test]
+fn test_muldiv() {
+    assert_eq!(mul_div_u64( 1_000_000_000_001, 1_000_000_000, 1_000_000),
+               1_000_000_000_001_000);
+}
diff --git a/src/libstd/sys_common/mutex.rs b/src/libstd/sys_common/mutex.rs
new file mode 100644
index 00000000000..d1a738770d3
--- /dev/null
+++ b/src/libstd/sys_common/mutex.rs
@@ -0,0 +1,66 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use sys::mutex as imp;
+
+/// An OS-based mutual exclusion lock.
+///
+/// This is the thinnest cross-platform wrapper around OS mutexes. All usage of
+/// this mutex is unsafe and it is recommended to instead use the safe wrapper
+/// at the top level of the crate instead of this type.
+pub struct Mutex(imp::Mutex);
+
+unsafe impl Sync for Mutex {}
+
+impl Mutex {
+    /// Creates a new mutex for use.
+    ///
+    /// Behavior is undefined if the mutex is moved after it is
+    /// first used with any of the functions below.
+    pub const fn new() -> Mutex { Mutex(imp::Mutex::new()) }
+
+    /// Prepare the mutex for use.
+    ///
+    /// This should be called once the mutex is at a stable memory address.
+    #[inline]
+    pub unsafe fn init(&mut self) { self.0.init() }
+
+    /// Locks the mutex blocking the current thread until it is available.
+    ///
+    /// Behavior is undefined if the mutex has been moved between this and any
+    /// previous function call.
+    #[inline]
+    pub unsafe fn lock(&self) { self.0.lock() }
+
+    /// Attempts to lock the mutex without blocking, returning whether it was
+    /// successfully acquired or not.
+    ///
+    /// Behavior is undefined if the mutex has been moved between this and any
+    /// previous function call.
+    #[inline]
+    pub unsafe fn try_lock(&self) -> bool { self.0.try_lock() }
+
+    /// Unlocks the mutex.
+    ///
+    /// Behavior is undefined if the current thread does not actually hold the
+    /// mutex.
+    #[inline]
+    pub unsafe fn unlock(&self) { self.0.unlock() }
+
+    /// Deallocates all resources associated with this mutex.
+    ///
+    /// Behavior is undefined if there are current or will be future users of
+    /// this mutex.
+    #[inline]
+    pub unsafe fn destroy(&self) { self.0.destroy() }
+}
+
+// not meant to be exported to the outside world, just the containing module
+pub fn raw(mutex: &Mutex) -> &imp::Mutex { &mutex.0 }
diff --git a/src/libstd/sys_common/net.rs b/src/libstd/sys_common/net.rs
new file mode 100644
index 00000000000..10ad61f4c80
--- /dev/null
+++ b/src/libstd/sys_common/net.rs
@@ -0,0 +1,633 @@
+// Copyright 2013-2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use cmp;
+use ffi::CString;
+use fmt;
+use io::{self, Error, ErrorKind};
+use libc::{c_int, c_void};
+use mem;
+use net::{SocketAddr, Shutdown, Ipv4Addr, Ipv6Addr};
+use ptr;
+use sys::net::{cvt, cvt_r, cvt_gai, Socket, init, wrlen_t};
+use sys::net::netc as c;
+use sys_common::{AsInner, FromInner, IntoInner};
+use time::Duration;
+
+#[cfg(any(target_os = "dragonfly", target_os = "freebsd",
+          target_os = "ios", target_os = "macos",
+          target_os = "openbsd", target_os = "netbsd",
+          target_os = "solaris", target_os = "haiku"))]
+use sys::net::netc::IPV6_JOIN_GROUP as IPV6_ADD_MEMBERSHIP;
+#[cfg(not(any(target_os = "dragonfly", target_os = "freebsd",
+              target_os = "ios", target_os = "macos",
+              target_os = "openbsd", target_os = "netbsd",
+              target_os = "solaris", target_os = "haiku")))]
+use sys::net::netc::IPV6_ADD_MEMBERSHIP;
+#[cfg(any(target_os = "dragonfly", target_os = "freebsd",
+          target_os = "ios", target_os = "macos",
+          target_os = "openbsd", target_os = "netbsd",
+          target_os = "solaris", target_os = "haiku"))]
+use sys::net::netc::IPV6_LEAVE_GROUP as IPV6_DROP_MEMBERSHIP;
+#[cfg(not(any(target_os = "dragonfly", target_os = "freebsd",
+              target_os = "ios", target_os = "macos",
+              target_os = "openbsd", target_os = "netbsd",
+              target_os = "solaris", target_os = "haiku")))]
+use sys::net::netc::IPV6_DROP_MEMBERSHIP;
+
+#[cfg(any(target_os = "linux", target_os = "android",
+          target_os = "dragonfly", target_os = "freebsd",
+          target_os = "openbsd", target_os = "netbsd",
+          target_os = "haiku", target_os = "bitrig"))]
+use libc::MSG_NOSIGNAL;
+#[cfg(not(any(target_os = "linux", target_os = "android",
+              target_os = "dragonfly", target_os = "freebsd",
+              target_os = "openbsd", target_os = "netbsd",
+              target_os = "haiku", target_os = "bitrig")))]
+const MSG_NOSIGNAL: c_int = 0x0;
+
+////////////////////////////////////////////////////////////////////////////////
+// sockaddr and misc bindings
+////////////////////////////////////////////////////////////////////////////////
+
+pub fn setsockopt<T>(sock: &Socket, opt: c_int, val: c_int,
+                     payload: T) -> io::Result<()> {
+    unsafe {
+        let payload = &payload as *const T as *const c_void;
+        cvt(c::setsockopt(*sock.as_inner(), opt, val, payload,
+                          mem::size_of::<T>() as c::socklen_t))?;
+        Ok(())
+    }
+}
+
+pub fn getsockopt<T: Copy>(sock: &Socket, opt: c_int,
+                       val: c_int) -> io::Result<T> {
+    unsafe {
+        let mut slot: T = mem::zeroed();
+        let mut len = mem::size_of::<T>() as c::socklen_t;
+        cvt(c::getsockopt(*sock.as_inner(), opt, val,
+                          &mut slot as *mut _ as *mut _,
+                          &mut len))?;
+        assert_eq!(len as usize, mem::size_of::<T>());
+        Ok(slot)
+    }
+}
+
+fn sockname<F>(f: F) -> io::Result<SocketAddr>
+    where F: FnOnce(*mut c::sockaddr, *mut c::socklen_t) -> c_int
+{
+    unsafe {
+        let mut storage: c::sockaddr_storage = mem::zeroed();
+        let mut len = mem::size_of_val(&storage) as c::socklen_t;
+        cvt(f(&mut storage as *mut _ as *mut _, &mut len))?;
+        sockaddr_to_addr(&storage, len as usize)
+    }
+}
+
+fn sockaddr_to_addr(storage: &c::sockaddr_storage,
+                    len: usize) -> io::Result<SocketAddr> {
+    match storage.ss_family as c_int {
+        c::AF_INET => {
+            assert!(len as usize >= mem::size_of::<c::sockaddr_in>());
+            Ok(SocketAddr::V4(FromInner::from_inner(unsafe {
+                *(storage as *const _ as *const c::sockaddr_in)
+            })))
+        }
+        c::AF_INET6 => {
+            assert!(len as usize >= mem::size_of::<c::sockaddr_in6>());
+            Ok(SocketAddr::V6(FromInner::from_inner(unsafe {
+                *(storage as *const _ as *const c::sockaddr_in6)
+            })))
+        }
+        _ => {
+            Err(Error::new(ErrorKind::InvalidInput, "invalid argument"))
+        }
+    }
+}
+
+#[cfg(target_os = "android")]
+fn to_ipv6mr_interface(value: u32) -> c_int {
+    value as c_int
+}
+
+#[cfg(not(target_os = "android"))]
+fn to_ipv6mr_interface(value: u32) -> ::libc::c_uint {
+    value as ::libc::c_uint
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// get_host_addresses
+////////////////////////////////////////////////////////////////////////////////
+
+pub struct LookupHost {
+    original: *mut c::addrinfo,
+    cur: *mut c::addrinfo,
+}
+
+impl Iterator for LookupHost {
+    type Item = SocketAddr;
+    fn next(&mut self) -> Option<SocketAddr> {
+        loop {
+            unsafe {
+                let cur = match self.cur.as_ref() {
+                    None => return None,
+                    Some(c) => c,
+                };
+                self.cur = cur.ai_next;
+                match sockaddr_to_addr(mem::transmute(cur.ai_addr),
+                                       cur.ai_addrlen as usize)
+                {
+                    Ok(addr) => return Some(addr),
+                    Err(_) => continue,
+                }
+            }
+        }
+    }
+}
+
+unsafe impl Sync for LookupHost {}
+unsafe impl Send for LookupHost {}
+
+impl Drop for LookupHost {
+    fn drop(&mut self) {
+        unsafe { c::freeaddrinfo(self.original) }
+    }
+}
+
+pub fn lookup_host(host: &str) -> io::Result<LookupHost> {
+    init();
+
+    let c_host = CString::new(host)?;
+    let hints = c::addrinfo {
+        ai_flags: 0,
+        ai_family: 0,
+        ai_socktype: c::SOCK_STREAM,
+        ai_protocol: 0,
+        ai_addrlen: 0,
+        ai_addr: ptr::null_mut(),
+        ai_canonname: ptr::null_mut(),
+        ai_next: ptr::null_mut()
+    };
+    let mut res = ptr::null_mut();
+    unsafe {
+        cvt_gai(c::getaddrinfo(c_host.as_ptr(), ptr::null(), &hints,
+                               &mut res))?;
+        Ok(LookupHost { original: res, cur: res })
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// TCP streams
+////////////////////////////////////////////////////////////////////////////////
+
+pub struct TcpStream {
+    inner: Socket,
+}
+
+impl TcpStream {
+    pub fn connect(addr: &SocketAddr) -> io::Result<TcpStream> {
+        init();
+
+        let sock = Socket::new(addr, c::SOCK_STREAM)?;
+
+        let (addrp, len) = addr.into_inner();
+        cvt_r(|| unsafe { c::connect(*sock.as_inner(), addrp, len) })?;
+        Ok(TcpStream { inner: sock })
+    }
+
+    pub fn socket(&self) -> &Socket { &self.inner }
+
+    pub fn into_socket(self) -> Socket { self.inner }
+
+    pub fn set_read_timeout(&self, dur: Option<Duration>) -> io::Result<()> {
+        self.inner.set_timeout(dur, c::SO_RCVTIMEO)
+    }
+
+    pub fn set_write_timeout(&self, dur: Option<Duration>) -> io::Result<()> {
+        self.inner.set_timeout(dur, c::SO_SNDTIMEO)
+    }
+
+    pub fn read_timeout(&self) -> io::Result<Option<Duration>> {
+        self.inner.timeout(c::SO_RCVTIMEO)
+    }
+
+    pub fn write_timeout(&self) -> io::Result<Option<Duration>> {
+        self.inner.timeout(c::SO_SNDTIMEO)
+    }
+
+    pub fn read(&self, buf: &mut [u8]) -> io::Result<usize> {
+        self.inner.read(buf)
+    }
+
+    pub fn read_to_end(&self, buf: &mut Vec<u8>) -> io::Result<usize> {
+        self.inner.read_to_end(buf)
+    }
+
+    pub fn write(&self, buf: &[u8]) -> io::Result<usize> {
+        let len = cmp::min(buf.len(), <wrlen_t>::max_value() as usize) as wrlen_t;
+        let ret = cvt(unsafe {
+            c::send(*self.inner.as_inner(),
+                    buf.as_ptr() as *const c_void,
+                    len,
+                    MSG_NOSIGNAL)
+        })?;
+        Ok(ret as usize)
+    }
+
+    pub fn peer_addr(&self) -> io::Result<SocketAddr> {
+        sockname(|buf, len| unsafe {
+            c::getpeername(*self.inner.as_inner(), buf, len)
+        })
+    }
+
+    pub fn socket_addr(&self) -> io::Result<SocketAddr> {
+        sockname(|buf, len| unsafe {
+            c::getsockname(*self.inner.as_inner(), buf, len)
+        })
+    }
+
+    pub fn shutdown(&self, how: Shutdown) -> io::Result<()> {
+        self.inner.shutdown(how)
+    }
+
+    pub fn duplicate(&self) -> io::Result<TcpStream> {
+        self.inner.duplicate().map(|s| TcpStream { inner: s })
+    }
+
+    pub fn set_nodelay(&self, nodelay: bool) -> io::Result<()> {
+        self.inner.set_nodelay(nodelay)
+    }
+
+    pub fn nodelay(&self) -> io::Result<bool> {
+        self.inner.nodelay()
+    }
+
+    pub fn set_ttl(&self, ttl: u32) -> io::Result<()> {
+        setsockopt(&self.inner, c::IPPROTO_IP, c::IP_TTL, ttl as c_int)
+    }
+
+    pub fn ttl(&self) -> io::Result<u32> {
+        let raw: c_int = getsockopt(&self.inner, c::IPPROTO_IP, c::IP_TTL)?;
+        Ok(raw as u32)
+    }
+
+    pub fn take_error(&self) -> io::Result<Option<io::Error>> {
+        self.inner.take_error()
+    }
+
+    pub fn set_nonblocking(&self, nonblocking: bool) -> io::Result<()> {
+        self.inner.set_nonblocking(nonblocking)
+    }
+}
+
+impl FromInner<Socket> for TcpStream {
+    fn from_inner(socket: Socket) -> TcpStream {
+        TcpStream { inner: socket }
+    }
+}
+
+impl fmt::Debug for TcpStream {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let mut res = f.debug_struct("TcpStream");
+
+        if let Ok(addr) = self.socket_addr() {
+            res.field("addr", &addr);
+        }
+
+        if let Ok(peer) = self.peer_addr() {
+            res.field("peer", &peer);
+        }
+
+        let name = if cfg!(windows) {"socket"} else {"fd"};
+        res.field(name, &self.inner.as_inner())
+            .finish()
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// TCP listeners
+////////////////////////////////////////////////////////////////////////////////
+
+pub struct TcpListener {
+    inner: Socket,
+}
+
+impl TcpListener {
+    pub fn bind(addr: &SocketAddr) -> io::Result<TcpListener> {
+        init();
+
+        let sock = Socket::new(addr, c::SOCK_STREAM)?;
+
+        // On platforms with Berkeley-derived sockets, this allows
+        // to quickly rebind a socket, without needing to wait for
+        // the OS to clean up the previous one.
+        if !cfg!(windows) {
+            setsockopt(&sock, c::SOL_SOCKET, c::SO_REUSEADDR,
+                       1 as c_int)?;
+        }
+
+        // Bind our new socket
+        let (addrp, len) = addr.into_inner();
+        cvt(unsafe { c::bind(*sock.as_inner(), addrp, len) })?;
+
+        // Start listening
+        cvt(unsafe { c::listen(*sock.as_inner(), 128) })?;
+        Ok(TcpListener { inner: sock })
+    }
+
+    pub fn socket(&self) -> &Socket { &self.inner }
+
+    pub fn into_socket(self) -> Socket { self.inner }
+
+    pub fn socket_addr(&self) -> io::Result<SocketAddr> {
+        sockname(|buf, len| unsafe {
+            c::getsockname(*self.inner.as_inner(), buf, len)
+        })
+    }
+
+    pub fn accept(&self) -> io::Result<(TcpStream, SocketAddr)> {
+        let mut storage: c::sockaddr_storage = unsafe { mem::zeroed() };
+        let mut len = mem::size_of_val(&storage) as c::socklen_t;
+        let sock = self.inner.accept(&mut storage as *mut _ as *mut _,
+                                     &mut len)?;
+        let addr = sockaddr_to_addr(&storage, len as usize)?;
+        Ok((TcpStream { inner: sock, }, addr))
+    }
+
+    pub fn duplicate(&self) -> io::Result<TcpListener> {
+        self.inner.duplicate().map(|s| TcpListener { inner: s })
+    }
+
+    pub fn set_ttl(&self, ttl: u32) -> io::Result<()> {
+        setsockopt(&self.inner, c::IPPROTO_IP, c::IP_TTL, ttl as c_int)
+    }
+
+    pub fn ttl(&self) -> io::Result<u32> {
+        let raw: c_int = getsockopt(&self.inner, c::IPPROTO_IP, c::IP_TTL)?;
+        Ok(raw as u32)
+    }
+
+    pub fn set_only_v6(&self, only_v6: bool) -> io::Result<()> {
+        setsockopt(&self.inner, c::IPPROTO_IPV6, c::IPV6_V6ONLY, only_v6 as c_int)
+    }
+
+    pub fn only_v6(&self) -> io::Result<bool> {
+        let raw: c_int = getsockopt(&self.inner, c::IPPROTO_IPV6, c::IPV6_V6ONLY)?;
+        Ok(raw != 0)
+    }
+
+    pub fn take_error(&self) -> io::Result<Option<io::Error>> {
+        self.inner.take_error()
+    }
+
+    pub fn set_nonblocking(&self, nonblocking: bool) -> io::Result<()> {
+        self.inner.set_nonblocking(nonblocking)
+    }
+}
+
+impl FromInner<Socket> for TcpListener {
+    fn from_inner(socket: Socket) -> TcpListener {
+        TcpListener { inner: socket }
+    }
+}
+
+impl fmt::Debug for TcpListener {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let mut res = f.debug_struct("TcpListener");
+
+        if let Ok(addr) = self.socket_addr() {
+            res.field("addr", &addr);
+        }
+
+        let name = if cfg!(windows) {"socket"} else {"fd"};
+        res.field(name, &self.inner.as_inner())
+            .finish()
+    }
+}
+
+////////////////////////////////////////////////////////////////////////////////
+// UDP
+////////////////////////////////////////////////////////////////////////////////
+
+pub struct UdpSocket {
+    inner: Socket,
+}
+
+impl UdpSocket {
+    pub fn bind(addr: &SocketAddr) -> io::Result<UdpSocket> {
+        init();
+
+        let sock = Socket::new(addr, c::SOCK_DGRAM)?;
+        let (addrp, len) = addr.into_inner();
+        cvt(unsafe { c::bind(*sock.as_inner(), addrp, len) })?;
+        Ok(UdpSocket { inner: sock })
+    }
+
+    pub fn socket(&self) -> &Socket { &self.inner }
+
+    pub fn into_socket(self) -> Socket { self.inner }
+
+    pub fn socket_addr(&self) -> io::Result<SocketAddr> {
+        sockname(|buf, len| unsafe {
+            c::getsockname(*self.inner.as_inner(), buf, len)
+        })
+    }
+
+    pub fn recv_from(&self, buf: &mut [u8]) -> io::Result<(usize, SocketAddr)> {
+        let mut storage: c::sockaddr_storage = unsafe { mem::zeroed() };
+        let mut addrlen = mem::size_of_val(&storage) as c::socklen_t;
+        let len = cmp::min(buf.len(), <wrlen_t>::max_value() as usize) as wrlen_t;
+
+        let n = cvt(unsafe {
+            c::recvfrom(*self.inner.as_inner(),
+                        buf.as_mut_ptr() as *mut c_void,
+                        len, 0,
+                        &mut storage as *mut _ as *mut _, &mut addrlen)
+        })?;
+        Ok((n as usize, sockaddr_to_addr(&storage, addrlen as usize)?))
+    }
+
+    pub fn send_to(&self, buf: &[u8], dst: &SocketAddr) -> io::Result<usize> {
+        let len = cmp::min(buf.len(), <wrlen_t>::max_value() as usize) as wrlen_t;
+        let (dstp, dstlen) = dst.into_inner();
+        let ret = cvt(unsafe {
+            c::sendto(*self.inner.as_inner(),
+                      buf.as_ptr() as *const c_void, len,
+                      MSG_NOSIGNAL, dstp, dstlen)
+        })?;
+        Ok(ret as usize)
+    }
+
+    pub fn duplicate(&self) -> io::Result<UdpSocket> {
+        self.inner.duplicate().map(|s| UdpSocket { inner: s })
+    }
+
+    pub fn set_read_timeout(&self, dur: Option<Duration>) -> io::Result<()> {
+        self.inner.set_timeout(dur, c::SO_RCVTIMEO)
+    }
+
+    pub fn set_write_timeout(&self, dur: Option<Duration>) -> io::Result<()> {
+        self.inner.set_timeout(dur, c::SO_SNDTIMEO)
+    }
+
+    pub fn read_timeout(&self) -> io::Result<Option<Duration>> {
+        self.inner.timeout(c::SO_RCVTIMEO)
+    }
+
+    pub fn write_timeout(&self) -> io::Result<Option<Duration>> {
+        self.inner.timeout(c::SO_SNDTIMEO)
+    }
+
+    pub fn set_broadcast(&self, broadcast: bool) -> io::Result<()> {
+        setsockopt(&self.inner, c::SOL_SOCKET, c::SO_BROADCAST, broadcast as c_int)
+    }
+
+    pub fn broadcast(&self) -> io::Result<bool> {
+        let raw: c_int = getsockopt(&self.inner, c::SOL_SOCKET, c::SO_BROADCAST)?;
+        Ok(raw != 0)
+    }
+
+    pub fn set_multicast_loop_v4(&self, multicast_loop_v4: bool) -> io::Result<()> {
+        setsockopt(&self.inner, c::IPPROTO_IP, c::IP_MULTICAST_LOOP, multicast_loop_v4 as c_int)
+    }
+
+    pub fn multicast_loop_v4(&self) -> io::Result<bool> {
+        let raw: c_int = getsockopt(&self.inner, c::IPPROTO_IP, c::IP_MULTICAST_LOOP)?;
+        Ok(raw != 0)
+    }
+
+    pub fn set_multicast_ttl_v4(&self, multicast_ttl_v4: u32) -> io::Result<()> {
+        setsockopt(&self.inner, c::IPPROTO_IP, c::IP_MULTICAST_TTL, multicast_ttl_v4 as c_int)
+    }
+
+    pub fn multicast_ttl_v4(&self) -> io::Result<u32> {
+        let raw: c_int = getsockopt(&self.inner, c::IPPROTO_IP, c::IP_MULTICAST_TTL)?;
+        Ok(raw as u32)
+    }
+
+    pub fn set_multicast_loop_v6(&self, multicast_loop_v6: bool) -> io::Result<()> {
+        setsockopt(&self.inner, c::IPPROTO_IPV6, c::IPV6_MULTICAST_LOOP, multicast_loop_v6 as c_int)
+    }
+
+    pub fn multicast_loop_v6(&self) -> io::Result<bool> {
+        let raw: c_int = getsockopt(&self.inner, c::IPPROTO_IPV6, c::IPV6_MULTICAST_LOOP)?;
+        Ok(raw != 0)
+    }
+
+    pub fn join_multicast_v4(&self, multiaddr: &Ipv4Addr, interface: &Ipv4Addr)
+                         -> io::Result<()> {
+        let mreq = c::ip_mreq {
+            imr_multiaddr: *multiaddr.as_inner(),
+            imr_interface: *interface.as_inner(),
+        };
+        setsockopt(&self.inner, c::IPPROTO_IP, c::IP_ADD_MEMBERSHIP, mreq)
+    }
+
+    pub fn join_multicast_v6(&self, multiaddr: &Ipv6Addr, interface: u32)
+                         -> io::Result<()> {
+        let mreq = c::ipv6_mreq {
+            ipv6mr_multiaddr: *multiaddr.as_inner(),
+            ipv6mr_interface: to_ipv6mr_interface(interface),
+        };
+        setsockopt(&self.inner, c::IPPROTO_IPV6, IPV6_ADD_MEMBERSHIP, mreq)
+    }
+
+    pub fn leave_multicast_v4(&self, multiaddr: &Ipv4Addr, interface: &Ipv4Addr)
+                          -> io::Result<()> {
+        let mreq = c::ip_mreq {
+            imr_multiaddr: *multiaddr.as_inner(),
+            imr_interface: *interface.as_inner(),
+        };
+        setsockopt(&self.inner, c::IPPROTO_IP, c::IP_DROP_MEMBERSHIP, mreq)
+    }
+
+    pub fn leave_multicast_v6(&self, multiaddr: &Ipv6Addr, interface: u32)
+                          -> io::Result<()> {
+        let mreq = c::ipv6_mreq {
+            ipv6mr_multiaddr: *multiaddr.as_inner(),
+            ipv6mr_interface: to_ipv6mr_interface(interface),
+        };
+        setsockopt(&self.inner, c::IPPROTO_IPV6, IPV6_DROP_MEMBERSHIP, mreq)
+    }
+
+    pub fn set_ttl(&self, ttl: u32) -> io::Result<()> {
+        setsockopt(&self.inner, c::IPPROTO_IP, c::IP_TTL, ttl as c_int)
+    }
+
+    pub fn ttl(&self) -> io::Result<u32> {
+        let raw: c_int = getsockopt(&self.inner, c::IPPROTO_IP, c::IP_TTL)?;
+        Ok(raw as u32)
+    }
+
+    pub fn take_error(&self) -> io::Result<Option<io::Error>> {
+        self.inner.take_error()
+    }
+
+    pub fn set_nonblocking(&self, nonblocking: bool) -> io::Result<()> {
+        self.inner.set_nonblocking(nonblocking)
+    }
+
+    pub fn recv(&self, buf: &mut [u8]) -> io::Result<usize> {
+        self.inner.read(buf)
+    }
+
+    pub fn send(&self, buf: &[u8]) -> io::Result<usize> {
+        let len = cmp::min(buf.len(), <wrlen_t>::max_value() as usize) as wrlen_t;
+        let ret = cvt(unsafe {
+            c::send(*self.inner.as_inner(),
+                    buf.as_ptr() as *const c_void,
+                    len,
+                    MSG_NOSIGNAL)
+        })?;
+        Ok(ret as usize)
+    }
+
+    pub fn connect(&self, addr: &SocketAddr) -> io::Result<()> {
+        let (addrp, len) = addr.into_inner();
+        cvt_r(|| unsafe { c::connect(*self.inner.as_inner(), addrp, len) }).map(|_| ())
+    }
+}
+
+impl FromInner<Socket> for UdpSocket {
+    fn from_inner(socket: Socket) -> UdpSocket {
+        UdpSocket { inner: socket }
+    }
+}
+
+impl fmt::Debug for UdpSocket {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        let mut res = f.debug_struct("UdpSocket");
+
+        if let Ok(addr) = self.socket_addr() {
+            res.field("addr", &addr);
+        }
+
+        let name = if cfg!(windows) {"socket"} else {"fd"};
+        res.field(name, &self.inner.as_inner())
+            .finish()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use collections::HashMap;
+
+    #[test]
+    fn no_lookup_host_duplicates() {
+        let mut addrs = HashMap::new();
+        let lh = match lookup_host("localhost") {
+            Ok(lh) => lh,
+            Err(e) => panic!("couldn't resolve `localhost': {}", e)
+        };
+        let _na = lh.map(|sa| *addrs.entry(sa).or_insert(0) += 1).count();
+        assert!(addrs.values().filter(|&&v| v > 1).count() == 0);
+    }
+}
diff --git a/src/libstd/sys_common/poison.rs b/src/libstd/sys_common/poison.rs
new file mode 100644
index 00000000000..bdc727f1dfc
--- /dev/null
+++ b/src/libstd/sys_common/poison.rs
@@ -0,0 +1,199 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use error::{Error};
+use fmt;
+use sync::atomic::{AtomicBool, Ordering};
+use thread;
+
+pub struct Flag { failed: AtomicBool }
+
+// Note that the Ordering uses to access the `failed` field of `Flag` below is
+// always `Relaxed`, and that's because this isn't actually protecting any data,
+// it's just a flag whether we've panicked or not.
+//
+// The actual location that this matters is when a mutex is **locked** which is
+// where we have external synchronization ensuring that we see memory
+// reads/writes to this flag.
+//
+// As a result, if it matters, we should see the correct value for `failed` in
+// all cases.
+
+impl Flag {
+    pub const fn new() -> Flag {
+        Flag { failed: AtomicBool::new(false) }
+    }
+
+    #[inline]
+    pub fn borrow(&self) -> LockResult<Guard> {
+        let ret = Guard { panicking: thread::panicking() };
+        if self.get() {
+            Err(PoisonError::new(ret))
+        } else {
+            Ok(ret)
+        }
+    }
+
+    #[inline]
+    pub fn done(&self, guard: &Guard) {
+        if !guard.panicking && thread::panicking() {
+            self.failed.store(true, Ordering::Relaxed);
+        }
+    }
+
+    #[inline]
+    pub fn get(&self) -> bool {
+        self.failed.load(Ordering::Relaxed)
+    }
+}
+
+pub struct Guard {
+    panicking: bool,
+}
+
+/// A type of error which can be returned whenever a lock is acquired.
+///
+/// Both Mutexes and RwLocks are poisoned whenever a thread fails while the lock
+/// is held. The precise semantics for when a lock is poisoned is documented on
+/// each lock, but once a lock is poisoned then all future acquisitions will
+/// return this error.
+#[stable(feature = "rust1", since = "1.0.0")]
+pub struct PoisonError<T> {
+    guard: T,
+}
+
+/// An enumeration of possible errors which can occur while calling the
+/// `try_lock` method.
+#[stable(feature = "rust1", since = "1.0.0")]
+pub enum TryLockError<T> {
+    /// The lock could not be acquired because another thread failed while holding
+    /// the lock.
+    #[stable(feature = "rust1", since = "1.0.0")]
+    Poisoned(#[stable(feature = "rust1", since = "1.0.0")] PoisonError<T>),
+    /// The lock could not be acquired at this time because the operation would
+    /// otherwise block.
+    #[stable(feature = "rust1", since = "1.0.0")]
+    WouldBlock,
+}
+
+/// A type alias for the result of a lock method which can be poisoned.
+///
+/// The `Ok` variant of this result indicates that the primitive was not
+/// poisoned, and the `Guard` is contained within. The `Err` variant indicates
+/// that the primitive was poisoned. Note that the `Err` variant *also* carries
+/// the associated guard, and it can be acquired through the `into_inner`
+/// method.
+#[stable(feature = "rust1", since = "1.0.0")]
+pub type LockResult<Guard> = Result<Guard, PoisonError<Guard>>;
+
+/// A type alias for the result of a nonblocking locking method.
+///
+/// For more information, see `LockResult`. A `TryLockResult` doesn't
+/// necessarily hold the associated guard in the `Err` type as the lock may not
+/// have been acquired for other reasons.
+#[stable(feature = "rust1", since = "1.0.0")]
+pub type TryLockResult<Guard> = Result<Guard, TryLockError<Guard>>;
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> fmt::Debug for PoisonError<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        "PoisonError { inner: .. }".fmt(f)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> fmt::Display for PoisonError<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        "poisoned lock: another task failed inside".fmt(f)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> Error for PoisonError<T> {
+    fn description(&self) -> &str {
+        "poisoned lock: another task failed inside"
+    }
+}
+
+impl<T> PoisonError<T> {
+    /// Creates a `PoisonError`.
+    #[stable(feature = "sync_poison", since = "1.2.0")]
+    pub fn new(guard: T) -> PoisonError<T> {
+        PoisonError { guard: guard }
+    }
+
+    /// Consumes this error indicating that a lock is poisoned, returning the
+    /// underlying guard to allow access regardless.
+    #[stable(feature = "sync_poison", since = "1.2.0")]
+    pub fn into_inner(self) -> T { self.guard }
+
+    /// Reaches into this error indicating that a lock is poisoned, returning a
+    /// reference to the underlying guard to allow access regardless.
+    #[stable(feature = "sync_poison", since = "1.2.0")]
+    pub fn get_ref(&self) -> &T { &self.guard }
+
+    /// Reaches into this error indicating that a lock is poisoned, returning a
+    /// mutable reference to the underlying guard to allow access regardless.
+    #[stable(feature = "sync_poison", since = "1.2.0")]
+    pub fn get_mut(&mut self) -> &mut T { &mut self.guard }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> From<PoisonError<T>> for TryLockError<T> {
+    fn from(err: PoisonError<T>) -> TryLockError<T> {
+        TryLockError::Poisoned(err)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> fmt::Debug for TryLockError<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            TryLockError::Poisoned(..) => "Poisoned(..)".fmt(f),
+            TryLockError::WouldBlock => "WouldBlock".fmt(f)
+        }
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> fmt::Display for TryLockError<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match *self {
+            TryLockError::Poisoned(..) => "poisoned lock: another task failed inside",
+            TryLockError::WouldBlock => "try_lock failed because the operation would block"
+        }.fmt(f)
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<T> Error for TryLockError<T> {
+    fn description(&self) -> &str {
+        match *self {
+            TryLockError::Poisoned(ref p) => p.description(),
+            TryLockError::WouldBlock => "try_lock failed because the operation would block"
+        }
+    }
+
+    fn cause(&self) -> Option<&Error> {
+        match *self {
+            TryLockError::Poisoned(ref p) => Some(p),
+            _ => None
+        }
+    }
+}
+
+pub fn map_result<T, U, F>(result: LockResult<T>, f: F)
+                           -> LockResult<U>
+                           where F: FnOnce(T) -> U {
+    match result {
+        Ok(t) => Ok(f(t)),
+        Err(PoisonError { guard }) => Err(PoisonError::new(f(guard)))
+    }
+}
diff --git a/src/libstd/sys_common/remutex.rs b/src/libstd/sys_common/remutex.rs
new file mode 100644
index 00000000000..4d0407ccf6c
--- /dev/null
+++ b/src/libstd/sys_common/remutex.rs
@@ -0,0 +1,236 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use fmt;
+use marker;
+use ops::Deref;
+use sys_common::poison::{self, TryLockError, TryLockResult, LockResult};
+use sys::mutex as sys;
+
+/// A re-entrant mutual exclusion
+///
+/// This mutex will block *other* threads waiting for the lock to become
+/// available. The thread which has already locked the mutex can lock it
+/// multiple times without blocking, preventing a common source of deadlocks.
+pub struct ReentrantMutex<T> {
+    inner: Box<sys::ReentrantMutex>,
+    poison: poison::Flag,
+    data: T,
+}
+
+unsafe impl<T: Send> Send for ReentrantMutex<T> {}
+unsafe impl<T: Send> Sync for ReentrantMutex<T> {}
+
+
+/// An RAII implementation of a "scoped lock" of a mutex. When this structure is
+/// dropped (falls out of scope), the lock will be unlocked.
+///
+/// The data protected by the mutex can be accessed through this guard via its
+/// Deref implementation.
+///
+/// # Mutability
+///
+/// Unlike `MutexGuard`, `ReentrantMutexGuard` does not implement `DerefMut`,
+/// because implementation of the trait would violate Rust’s reference aliasing
+/// rules. Use interior mutability (usually `RefCell`) in order to mutate the
+/// guarded data.
+#[must_use]
+pub struct ReentrantMutexGuard<'a, T: 'a> {
+    // funny underscores due to how Deref currently works (it disregards field
+    // privacy).
+    __lock: &'a ReentrantMutex<T>,
+    __poison: poison::Guard,
+}
+
+impl<'a, T> !marker::Send for ReentrantMutexGuard<'a, T> {}
+
+
+impl<T> ReentrantMutex<T> {
+    /// Creates a new reentrant mutex in an unlocked state.
+    pub fn new(t: T) -> ReentrantMutex<T> {
+        unsafe {
+            let mut mutex = ReentrantMutex {
+                inner: box sys::ReentrantMutex::uninitialized(),
+                poison: poison::Flag::new(),
+                data: t,
+            };
+            mutex.inner.init();
+            mutex
+        }
+    }
+
+    /// Acquires a mutex, blocking the current thread until it is able to do so.
+    ///
+    /// This function will block the caller until it is available to acquire the mutex.
+    /// Upon returning, the thread is the only thread with the mutex held. When the thread
+    /// calling this method already holds the lock, the call shall succeed without
+    /// blocking.
+    ///
+    /// # Errors
+    ///
+    /// If another user of this mutex panicked while holding the mutex, then
+    /// this call will return failure if the mutex would otherwise be
+    /// acquired.
+    pub fn lock(&self) -> LockResult<ReentrantMutexGuard<T>> {
+        unsafe { self.inner.lock() }
+        ReentrantMutexGuard::new(&self)
+    }
+
+    /// Attempts to acquire this lock.
+    ///
+    /// If the lock could not be acquired at this time, then `Err` is returned.
+    /// Otherwise, an RAII guard is returned.
+    ///
+    /// This function does not block.
+    ///
+    /// # Errors
+    ///
+    /// If another user of this mutex panicked while holding the mutex, then
+    /// this call will return failure if the mutex would otherwise be
+    /// acquired.
+    pub fn try_lock(&self) -> TryLockResult<ReentrantMutexGuard<T>> {
+        if unsafe { self.inner.try_lock() } {
+            Ok(ReentrantMutexGuard::new(&self)?)
+        } else {
+            Err(TryLockError::WouldBlock)
+        }
+    }
+}
+
+impl<T> Drop for ReentrantMutex<T> {
+    fn drop(&mut self) {
+        // This is actually safe b/c we know that there is no further usage of
+        // this mutex (it's up to the user to arrange for a mutex to get
+        // dropped, that's not our job)
+        unsafe { self.inner.destroy() }
+    }
+}
+
+impl<T: fmt::Debug + 'static> fmt::Debug for ReentrantMutex<T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        match self.try_lock() {
+            Ok(guard) => write!(f, "ReentrantMutex {{ data: {:?} }}", &*guard),
+            Err(TryLockError::Poisoned(err)) => {
+                write!(f, "ReentrantMutex {{ data: Poisoned({:?}) }}", &**err.get_ref())
+            },
+            Err(TryLockError::WouldBlock) => write!(f, "ReentrantMutex {{ <locked> }}")
+        }
+    }
+}
+
+impl<'mutex, T> ReentrantMutexGuard<'mutex, T> {
+    fn new(lock: &'mutex ReentrantMutex<T>)
+            -> LockResult<ReentrantMutexGuard<'mutex, T>> {
+        poison::map_result(lock.poison.borrow(), |guard| {
+            ReentrantMutexGuard {
+                __lock: lock,
+                __poison: guard,
+            }
+        })
+    }
+}
+
+impl<'mutex, T> Deref for ReentrantMutexGuard<'mutex, T> {
+    type Target = T;
+
+    fn deref(&self) -> &T {
+        &self.__lock.data
+    }
+}
+
+impl<'a, T> Drop for ReentrantMutexGuard<'a, T> {
+    #[inline]
+    fn drop(&mut self) {
+        unsafe {
+            self.__lock.poison.done(&self.__poison);
+            self.__lock.inner.unlock();
+        }
+    }
+}
+
+
+#[cfg(all(test, not(target_os = "emscripten")))]
+mod tests {
+    use sys_common::remutex::{ReentrantMutex, ReentrantMutexGuard};
+    use cell::RefCell;
+    use sync::Arc;
+    use thread;
+
+    #[test]
+    fn smoke() {
+        let m = ReentrantMutex::new(());
+        {
+            let a = m.lock().unwrap();
+            {
+                let b = m.lock().unwrap();
+                {
+                    let c = m.lock().unwrap();
+                    assert_eq!(*c, ());
+                }
+                assert_eq!(*b, ());
+            }
+            assert_eq!(*a, ());
+        }
+    }
+
+    #[test]
+    fn is_mutex() {
+        let m = Arc::new(ReentrantMutex::new(RefCell::new(0)));
+        let m2 = m.clone();
+        let lock = m.lock().unwrap();
+        let child = thread::spawn(move || {
+            let lock = m2.lock().unwrap();
+            assert_eq!(*lock.borrow(), 4950);
+        });
+        for i in 0..100 {
+            let lock = m.lock().unwrap();
+            *lock.borrow_mut() += i;
+        }
+        drop(lock);
+        child.join().unwrap();
+    }
+
+    #[test]
+    fn trylock_works() {
+        let m = Arc::new(ReentrantMutex::new(()));
+        let m2 = m.clone();
+        let _lock = m.try_lock().unwrap();
+        let _lock2 = m.try_lock().unwrap();
+        thread::spawn(move || {
+            let lock = m2.try_lock();
+            assert!(lock.is_err());
+        }).join().unwrap();
+        let _lock3 = m.try_lock().unwrap();
+    }
+
+    pub struct Answer<'a>(pub ReentrantMutexGuard<'a, RefCell<u32>>);
+    impl<'a> Drop for Answer<'a> {
+        fn drop(&mut self) {
+            *self.0.borrow_mut() = 42;
+        }
+    }
+
+    #[test]
+    fn poison_works() {
+        let m = Arc::new(ReentrantMutex::new(RefCell::new(0)));
+        let mc = m.clone();
+        let result = thread::spawn(move ||{
+            let lock = mc.lock().unwrap();
+            *lock.borrow_mut() = 1;
+            let lock2 = mc.lock().unwrap();
+            *lock.borrow_mut() = 2;
+            let _answer = Answer(lock2);
+            panic!("What the answer to my lifetimes dilemma is?");
+        }).join();
+        assert!(result.is_err());
+        let r = m.lock().err().unwrap().into_inner();
+        assert_eq!(*r.borrow(), 42);
+    }
+}
diff --git a/src/libstd/sys_common/rwlock.rs b/src/libstd/sys_common/rwlock.rs
new file mode 100644
index 00000000000..71a4f01ec4c
--- /dev/null
+++ b/src/libstd/sys_common/rwlock.rs
@@ -0,0 +1,82 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use sys::rwlock as imp;
+
+/// An OS-based reader-writer lock.
+///
+/// This structure is entirely unsafe and serves as the lowest layer of a
+/// cross-platform binding of system rwlocks. It is recommended to use the
+/// safer types at the top level of this crate instead of this type.
+pub struct RWLock(imp::RWLock);
+
+impl RWLock {
+    /// Creates a new reader-writer lock for use.
+    ///
+    /// Behavior is undefined if the reader-writer lock is moved after it is
+    /// first used with any of the functions below.
+    pub const fn new() -> RWLock { RWLock(imp::RWLock::new()) }
+
+    /// Acquires shared access to the underlying lock, blocking the current
+    /// thread to do so.
+    ///
+    /// Behavior is undefined if the rwlock has been moved between this and any
+    /// previous method call.
+    #[inline]
+    pub unsafe fn read(&self) { self.0.read() }
+
+    /// Attempts to acquire shared access to this lock, returning whether it
+    /// succeeded or not.
+    ///
+    /// This function does not block the current thread.
+    ///
+    /// Behavior is undefined if the rwlock has been moved between this and any
+    /// previous method call.
+    #[inline]
+    pub unsafe fn try_read(&self) -> bool { self.0.try_read() }
+
+    /// Acquires write access to the underlying lock, blocking the current thread
+    /// to do so.
+    ///
+    /// Behavior is undefined if the rwlock has been moved between this and any
+    /// previous method call.
+    #[inline]
+    pub unsafe fn write(&self) { self.0.write() }
+
+    /// Attempts to acquire exclusive access to this lock, returning whether it
+    /// succeeded or not.
+    ///
+    /// This function does not block the current thread.
+    ///
+    /// Behavior is undefined if the rwlock has been moved between this and any
+    /// previous method call.
+    #[inline]
+    pub unsafe fn try_write(&self) -> bool { self.0.try_write() }
+
+    /// Unlocks previously acquired shared access to this lock.
+    ///
+    /// Behavior is undefined if the current thread does not have shared access.
+    #[inline]
+    pub unsafe fn read_unlock(&self) { self.0.read_unlock() }
+
+    /// Unlocks previously acquired exclusive access to this lock.
+    ///
+    /// Behavior is undefined if the current thread does not currently have
+    /// exclusive access.
+    #[inline]
+    pub unsafe fn write_unlock(&self) { self.0.write_unlock() }
+
+    /// Destroys OS-related resources with this RWLock.
+    ///
+    /// Behavior is undefined if there are any currently active users of this
+    /// lock.
+    #[inline]
+    pub unsafe fn destroy(&self) { self.0.destroy() }
+}
diff --git a/src/libstd/sys_common/thread.rs b/src/libstd/sys_common/thread.rs
new file mode 100644
index 00000000000..3ee160da5fa
--- /dev/null
+++ b/src/libstd/sys_common/thread.rs
@@ -0,0 +1,22 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use alloc::boxed::FnBox;
+use libc;
+use sys::stack_overflow;
+
+pub unsafe fn start_thread(main: *mut libc::c_void) {
+    // Next, set up our stack overflow handler which may get triggered if we run
+    // out of stack.
+    let _handler = stack_overflow::Handler::new();
+
+    // Finally, let's run some code.
+    Box::from_raw(main as *mut Box<FnBox()>)()
+}
diff --git a/src/libstd/sys_common/thread_info.rs b/src/libstd/sys_common/thread_info.rs
new file mode 100644
index 00000000000..95d8b6cc951
--- /dev/null
+++ b/src/libstd/sys_common/thread_info.rs
@@ -0,0 +1,61 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![allow(dead_code)] // stack_guard isn't used right now on all platforms
+
+use cell::RefCell;
+use thread::Thread;
+use thread::LocalKeyState;
+
+struct ThreadInfo {
+    stack_guard: Option<usize>,
+    thread: Thread,
+}
+
+thread_local! { static THREAD_INFO: RefCell<Option<ThreadInfo>> = RefCell::new(None) }
+
+impl ThreadInfo {
+    fn with<R, F>(f: F) -> Option<R> where F: FnOnce(&mut ThreadInfo) -> R {
+        if THREAD_INFO.state() == LocalKeyState::Destroyed {
+            return None
+        }
+
+        THREAD_INFO.with(move |c| {
+            if c.borrow().is_none() {
+                *c.borrow_mut() = Some(ThreadInfo {
+                    stack_guard: None,
+                    thread: NewThread::new(None),
+                })
+            }
+            Some(f(c.borrow_mut().as_mut().unwrap()))
+        })
+    }
+}
+
+pub fn current_thread() -> Option<Thread> {
+    ThreadInfo::with(|info| info.thread.clone())
+}
+
+pub fn stack_guard() -> Option<usize> {
+    ThreadInfo::with(|info| info.stack_guard).and_then(|o| o)
+}
+
+pub fn set(stack_guard: Option<usize>, thread: Thread) {
+    THREAD_INFO.with(|c| assert!(c.borrow().is_none()));
+    THREAD_INFO.with(move |c| *c.borrow_mut() = Some(ThreadInfo{
+        stack_guard: stack_guard,
+        thread: thread,
+    }));
+}
+
+// a hack to get around privacy restrictions; implemented by `std::thread`
+pub trait NewThread {
+    fn new(name: Option<String>) -> Self;
+}
diff --git a/src/libstd/sys_common/thread_local.rs b/src/libstd/sys_common/thread_local.rs
new file mode 100644
index 00000000000..25a9d5720d9
--- /dev/null
+++ b/src/libstd/sys_common/thread_local.rs
@@ -0,0 +1,270 @@
+// Copyright 2014 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! OS-based thread local storage
+//!
+//! This module provides an implementation of OS-based thread local storage,
+//! using the native OS-provided facilities (think `TlsAlloc` or
+//! `pthread_setspecific`). The interface of this differs from the other types
+//! of thread-local-storage provided in this crate in that OS-based TLS can only
+//! get/set pointers,
+//!
+//! This module also provides two flavors of TLS. One is intended for static
+//! initialization, and does not contain a `Drop` implementation to deallocate
+//! the OS-TLS key. The other is a type which does implement `Drop` and hence
+//! has a safe interface.
+//!
+//! # Usage
+//!
+//! This module should likely not be used directly unless other primitives are
+//! being built on. types such as `thread_local::spawn::Key` are likely much
+//! more useful in practice than this OS-based version which likely requires
+//! unsafe code to interoperate with.
+//!
+//! # Examples
+//!
+//! Using a dynamically allocated TLS key. Note that this key can be shared
+//! among many threads via an `Arc`.
+//!
+//! ```rust,ignore
+//! let key = Key::new(None);
+//! assert!(key.get().is_null());
+//! key.set(1 as *mut u8);
+//! assert!(!key.get().is_null());
+//!
+//! drop(key); // deallocate this TLS slot.
+//! ```
+//!
+//! Sometimes a statically allocated key is either required or easier to work
+//! with, however.
+//!
+//! ```rust,ignore
+//! static KEY: StaticKey = INIT;
+//!
+//! unsafe {
+//!     assert!(KEY.get().is_null());
+//!     KEY.set(1 as *mut u8);
+//! }
+//! ```
+
+#![allow(non_camel_case_types)]
+#![unstable(feature = "thread_local_internals", issue = "0")]
+#![allow(dead_code)] // sys isn't exported yet
+
+use sync::atomic::{self, AtomicUsize, Ordering};
+
+use sys::thread_local as imp;
+
+/// A type for TLS keys that are statically allocated.
+///
+/// This type is entirely `unsafe` to use as it does not protect against
+/// use-after-deallocation or use-during-deallocation.
+///
+/// The actual OS-TLS key is lazily allocated when this is used for the first
+/// time. The key is also deallocated when the Rust runtime exits or `destroy`
+/// is called, whichever comes first.
+///
+/// # Examples
+///
+/// ```ignore
+/// use tls::os::{StaticKey, INIT};
+///
+/// static KEY: StaticKey = INIT;
+///
+/// unsafe {
+///     assert!(KEY.get().is_null());
+///     KEY.set(1 as *mut u8);
+/// }
+/// ```
+pub struct StaticKey {
+    /// Inner static TLS key (internals).
+    key: AtomicUsize,
+    /// Destructor for the TLS value.
+    ///
+    /// See `Key::new` for information about when the destructor runs and how
+    /// it runs.
+    dtor: Option<unsafe extern fn(*mut u8)>,
+}
+
+/// A type for a safely managed OS-based TLS slot.
+///
+/// This type allocates an OS TLS key when it is initialized and will deallocate
+/// the key when it falls out of scope. When compared with `StaticKey`, this
+/// type is entirely safe to use.
+///
+/// Implementations will likely, however, contain unsafe code as this type only
+/// operates on `*mut u8`, a raw pointer.
+///
+/// # Examples
+///
+/// ```rust,ignore
+/// use tls::os::Key;
+///
+/// let key = Key::new(None);
+/// assert!(key.get().is_null());
+/// key.set(1 as *mut u8);
+/// assert!(!key.get().is_null());
+///
+/// drop(key); // deallocate this TLS slot.
+/// ```
+pub struct Key {
+    key: imp::Key,
+}
+
+/// Constant initialization value for static TLS keys.
+///
+/// This value specifies no destructor by default.
+pub const INIT: StaticKey = StaticKey::new(None);
+
+impl StaticKey {
+    pub const fn new(dtor: Option<unsafe extern fn(*mut u8)>) -> StaticKey {
+        StaticKey {
+            key: atomic::AtomicUsize::new(0),
+            dtor: dtor
+        }
+    }
+
+    /// Gets the value associated with this TLS key
+    ///
+    /// This will lazily allocate a TLS key from the OS if one has not already
+    /// been allocated.
+    #[inline]
+    pub unsafe fn get(&self) -> *mut u8 { imp::get(self.key()) }
+
+    /// Sets this TLS key to a new value.
+    ///
+    /// This will lazily allocate a TLS key from the OS if one has not already
+    /// been allocated.
+    #[inline]
+    pub unsafe fn set(&self, val: *mut u8) { imp::set(self.key(), val) }
+
+    /// Deallocates this OS TLS key.
+    ///
+    /// This function is unsafe as there is no guarantee that the key is not
+    /// currently in use by other threads or will not ever be used again.
+    ///
+    /// Note that this does *not* run the user-provided destructor if one was
+    /// specified at definition time. Doing so must be done manually.
+    pub unsafe fn destroy(&self) {
+        match self.key.swap(0, Ordering::SeqCst) {
+            0 => {}
+            n => { imp::destroy(n as imp::Key) }
+        }
+    }
+
+    #[inline]
+    unsafe fn key(&self) -> imp::Key {
+        match self.key.load(Ordering::Relaxed) {
+            0 => self.lazy_init() as imp::Key,
+            n => n as imp::Key
+        }
+    }
+
+    unsafe fn lazy_init(&self) -> usize {
+        // POSIX allows the key created here to be 0, but the compare_and_swap
+        // below relies on using 0 as a sentinel value to check who won the
+        // race to set the shared TLS key. As far as I know, there is no
+        // guaranteed value that cannot be returned as a posix_key_create key,
+        // so there is no value we can initialize the inner key with to
+        // prove that it has not yet been set. As such, we'll continue using a
+        // value of 0, but with some gyrations to make sure we have a non-0
+        // value returned from the creation routine.
+        // FIXME: this is clearly a hack, and should be cleaned up.
+        let key1 = imp::create(self.dtor);
+        let key = if key1 != 0 {
+            key1
+        } else {
+            let key2 = imp::create(self.dtor);
+            imp::destroy(key1);
+            key2
+        };
+        assert!(key != 0);
+        match self.key.compare_and_swap(0, key as usize, Ordering::SeqCst) {
+            // The CAS succeeded, so we've created the actual key
+            0 => key as usize,
+            // If someone beat us to the punch, use their key instead
+            n => { imp::destroy(key); n }
+        }
+    }
+}
+
+impl Key {
+    /// Creates a new managed OS TLS key.
+    ///
+    /// This key will be deallocated when the key falls out of scope.
+    ///
+    /// The argument provided is an optionally-specified destructor for the
+    /// value of this TLS key. When a thread exits and the value for this key
+    /// is non-null the destructor will be invoked. The TLS value will be reset
+    /// to null before the destructor is invoked.
+    ///
+    /// Note that the destructor will not be run when the `Key` goes out of
+    /// scope.
+    #[inline]
+    pub fn new(dtor: Option<unsafe extern fn(*mut u8)>) -> Key {
+        Key { key: unsafe { imp::create(dtor) } }
+    }
+
+    /// See StaticKey::get
+    #[inline]
+    pub fn get(&self) -> *mut u8 {
+        unsafe { imp::get(self.key) }
+    }
+
+    /// See StaticKey::set
+    #[inline]
+    pub fn set(&self, val: *mut u8) {
+        unsafe { imp::set(self.key, val) }
+    }
+}
+
+impl Drop for Key {
+    fn drop(&mut self) {
+        unsafe { imp::destroy(self.key) }
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{Key, StaticKey};
+
+    fn assert_sync<T: Sync>() {}
+    fn assert_send<T: Send>() {}
+
+    #[test]
+    fn smoke() {
+        assert_sync::<Key>();
+        assert_send::<Key>();
+
+        let k1 = Key::new(None);
+        let k2 = Key::new(None);
+        assert!(k1.get().is_null());
+        assert!(k2.get().is_null());
+        k1.set(1 as *mut _);
+        k2.set(2 as *mut _);
+        assert_eq!(k1.get() as usize, 1);
+        assert_eq!(k2.get() as usize, 2);
+    }
+
+    #[test]
+    fn statik() {
+        static K1: StaticKey = StaticKey::new(None);
+        static K2: StaticKey = StaticKey::new(None);
+
+        unsafe {
+            assert!(K1.get().is_null());
+            assert!(K2.get().is_null());
+            K1.set(1 as *mut _);
+            K2.set(2 as *mut _);
+            assert_eq!(K1.get() as usize, 1);
+            assert_eq!(K2.get() as usize, 2);
+        }
+    }
+}
diff --git a/src/libstd/sys_common/util.rs b/src/libstd/sys_common/util.rs
new file mode 100644
index 00000000000..daa0c15920b
--- /dev/null
+++ b/src/libstd/sys_common/util.rs
@@ -0,0 +1,50 @@
+// Copyright 2013 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use env;
+use fmt;
+use io::prelude::*;
+use sync::atomic::{self, Ordering};
+use sys::stdio::Stderr;
+use thread;
+
+pub fn min_stack() -> usize {
+    static MIN: atomic::AtomicUsize = atomic::AtomicUsize::new(0);
+    match MIN.load(Ordering::SeqCst) {
+        0 => {}
+        n => return n - 1,
+    }
+    let amt = env::var("RUST_MIN_STACK").ok().and_then(|s| s.parse().ok());
+    let amt = amt.unwrap_or(2 * 1024 * 1024);
+    // 0 is our sentinel value, so ensure that we'll never see 0 after
+    // initialization has run
+    MIN.store(amt + 1, Ordering::SeqCst);
+    amt
+}
+
+pub fn dumb_print(args: fmt::Arguments) {
+    let _ = Stderr::new().map(|mut stderr| stderr.write_fmt(args));
+}
+
+// Other platforms should use the appropriate platform-specific mechanism for
+// aborting the process.  If no platform-specific mechanism is available,
+// ::intrinsics::abort() may be used instead.  The above implementations cover
+// all targets currently supported by libstd.
+
+pub fn abort(args: fmt::Arguments) -> ! {
+    dumb_print(format_args!("fatal runtime error: {}\n", args));
+    unsafe { ::sys::abort_internal(); }
+}
+
+#[allow(dead_code)] // stack overflow detection not enabled on all platforms
+pub unsafe fn report_overflow() {
+    dumb_print(format_args!("\nthread '{}' has overflowed its stack\n",
+                            thread::current().name().unwrap_or("<unknown>")));
+}
diff --git a/src/libstd/sys_common/wtf8.rs b/src/libstd/sys_common/wtf8.rs
new file mode 100644
index 00000000000..0a94ff1e958
--- /dev/null
+++ b/src/libstd/sys_common/wtf8.rs
@@ -0,0 +1,1180 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Implementation of [the WTF-8 encoding](https://simonsapin.github.io/wtf-8/).
+//!
+//! This library uses Rust’s type system to maintain
+//! [well-formedness](https://simonsapin.github.io/wtf-8/#well-formed),
+//! like the `String` and `&str` types do for UTF-8.
+//!
+//! Since [WTF-8 must not be used
+//! for interchange](https://simonsapin.github.io/wtf-8/#intended-audience),
+//! this library deliberately does not provide access to the underlying bytes
+//! of WTF-8 strings,
+//! nor can it decode WTF-8 from arbitrary bytes.
+//! WTF-8 strings can be obtained from UTF-8, UTF-16, or code points.
+
+// this module is imported from @SimonSapin's repo and has tons of dead code on
+// unix (it's mostly used on windows), so don't worry about dead code here.
+#![allow(dead_code)]
+
+use core::str::next_code_point;
+
+use ascii::*;
+use borrow::Cow;
+use char;
+use fmt;
+use hash::{Hash, Hasher};
+use iter::FromIterator;
+use mem;
+use ops;
+use slice;
+use str;
+use sys_common::AsInner;
+
+const UTF8_REPLACEMENT_CHARACTER: &'static [u8] = b"\xEF\xBF\xBD";
+
+/// A Unicode code point: from U+0000 to U+10FFFF.
+///
+/// Compare with the `char` type,
+/// which represents a Unicode scalar value:
+/// a code point that is not a surrogate (U+D800 to U+DFFF).
+#[derive(Eq, PartialEq, Ord, PartialOrd, Clone, Copy)]
+pub struct CodePoint {
+    value: u32
+}
+
+/// Format the code point as `U+` followed by four to six hexadecimal digits.
+/// Example: `U+1F4A9`
+impl fmt::Debug for CodePoint {
+    #[inline]
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+        write!(formatter, "U+{:04X}", self.value)
+    }
+}
+
+impl CodePoint {
+    /// Unsafely creates a new `CodePoint` without checking the value.
+    ///
+    /// Only use when `value` is known to be less than or equal to 0x10FFFF.
+    #[inline]
+    pub unsafe fn from_u32_unchecked(value: u32) -> CodePoint {
+        CodePoint { value: value }
+    }
+
+    /// Creates a new `CodePoint` if the value is a valid code point.
+    ///
+    /// Returns `None` if `value` is above 0x10FFFF.
+    #[inline]
+    pub fn from_u32(value: u32) -> Option<CodePoint> {
+        match value {
+            0 ... 0x10FFFF => Some(CodePoint { value: value }),
+            _ => None
+        }
+    }
+
+    /// Creates a new `CodePoint` from a `char`.
+    ///
+    /// Since all Unicode scalar values are code points, this always succeeds.
+    #[inline]
+    pub fn from_char(value: char) -> CodePoint {
+        CodePoint { value: value as u32 }
+    }
+
+    /// Returns the numeric value of the code point.
+    #[inline]
+    pub fn to_u32(&self) -> u32 {
+        self.value
+    }
+
+    /// Optionally returns a Unicode scalar value for the code point.
+    ///
+    /// Returns `None` if the code point is a surrogate (from U+D800 to U+DFFF).
+    #[inline]
+    pub fn to_char(&self) -> Option<char> {
+        match self.value {
+            0xD800 ... 0xDFFF => None,
+            _ => Some(unsafe { char::from_u32_unchecked(self.value) })
+        }
+    }
+
+    /// Returns a Unicode scalar value for the code point.
+    ///
+    /// Returns `'\u{FFFD}'` (the replacement character “�”)
+    /// if the code point is a surrogate (from U+D800 to U+DFFF).
+    #[inline]
+    pub fn to_char_lossy(&self) -> char {
+        self.to_char().unwrap_or('\u{FFFD}')
+    }
+}
+
+/// An owned, growable string of well-formed WTF-8 data.
+///
+/// Similar to `String`, but can additionally contain surrogate code points
+/// if they’re not in a surrogate pair.
+#[derive(Eq, PartialEq, Ord, PartialOrd, Clone)]
+pub struct Wtf8Buf {
+    bytes: Vec<u8>
+}
+
+impl ops::Deref for Wtf8Buf {
+    type Target = Wtf8;
+
+    fn deref(&self) -> &Wtf8 {
+        self.as_slice()
+    }
+}
+
+/// Format the string with double quotes,
+/// and surrogates as `\u` followed by four hexadecimal digits.
+/// Example: `"a\u{D800}"` for a string with code points [U+0061, U+D800]
+impl fmt::Debug for Wtf8Buf {
+    #[inline]
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> Result<(), fmt::Error> {
+        fmt::Debug::fmt(&**self, formatter)
+    }
+}
+
+impl Wtf8Buf {
+    /// Creates a new, empty WTF-8 string.
+    #[inline]
+    pub fn new() -> Wtf8Buf {
+        Wtf8Buf { bytes: Vec::new() }
+    }
+
+    /// Creates a new, empty WTF-8 string with pre-allocated capacity for `n` bytes.
+    #[inline]
+    pub fn with_capacity(n: usize) -> Wtf8Buf {
+        Wtf8Buf { bytes: Vec::with_capacity(n) }
+    }
+
+    /// Creates a WTF-8 string from a UTF-8 `String`.
+    ///
+    /// This takes ownership of the `String` and does not copy.
+    ///
+    /// Since WTF-8 is a superset of UTF-8, this always succeeds.
+    #[inline]
+    pub fn from_string(string: String) -> Wtf8Buf {
+        Wtf8Buf { bytes: string.into_bytes() }
+    }
+
+    /// Creates a WTF-8 string from a UTF-8 `&str` slice.
+    ///
+    /// This copies the content of the slice.
+    ///
+    /// Since WTF-8 is a superset of UTF-8, this always succeeds.
+    #[inline]
+    pub fn from_str(str: &str) -> Wtf8Buf {
+        Wtf8Buf { bytes: <[_]>::to_vec(str.as_bytes()) }
+    }
+
+    pub fn clear(&mut self) {
+        self.bytes.clear()
+    }
+
+    /// Creates a WTF-8 string from a potentially ill-formed UTF-16 slice of 16-bit code units.
+    ///
+    /// This is lossless: calling `.encode_wide()` on the resulting string
+    /// will always return the original code units.
+    pub fn from_wide(v: &[u16]) -> Wtf8Buf {
+        let mut string = Wtf8Buf::with_capacity(v.len());
+        for item in char::decode_utf16(v.iter().cloned()) {
+            match item {
+                Ok(ch) => string.push_char(ch),
+                Err(surrogate) => {
+                    let surrogate = surrogate.unpaired_surrogate();
+                    // Surrogates are known to be in the code point range.
+                    let code_point = unsafe {
+                        CodePoint::from_u32_unchecked(surrogate as u32)
+                    };
+                    // Skip the WTF-8 concatenation check,
+                    // surrogate pairs are already decoded by decode_utf16
+                    string.push_code_point_unchecked(code_point)
+                }
+            }
+        }
+        string
+    }
+
+    /// Copied from String::push
+    /// This does **not** include the WTF-8 concatenation check.
+    fn push_code_point_unchecked(&mut self, code_point: CodePoint) {
+        let c = unsafe {
+            char::from_u32_unchecked(code_point.value)
+        };
+        let mut bytes = [0; 4];
+        let bytes = c.encode_utf8(&mut bytes).as_bytes();
+        self.bytes.extend_from_slice(bytes)
+    }
+
+    #[inline]
+    pub fn as_slice(&self) -> &Wtf8 {
+        unsafe { Wtf8::from_bytes_unchecked(&self.bytes) }
+    }
+
+    /// Reserves capacity for at least `additional` more bytes to be inserted
+    /// in the given `Wtf8Buf`.
+    /// The collection may reserve more space to avoid frequent reallocations.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the new capacity overflows `usize`.
+    #[inline]
+    pub fn reserve(&mut self, additional: usize) {
+        self.bytes.reserve(additional)
+    }
+
+    #[inline]
+    pub fn reserve_exact(&mut self, additional: usize) {
+        self.bytes.reserve_exact(additional)
+    }
+
+    /// Returns the number of bytes that this string buffer can hold without reallocating.
+    #[inline]
+    pub fn capacity(&self) -> usize {
+        self.bytes.capacity()
+    }
+
+    /// Append a UTF-8 slice at the end of the string.
+    #[inline]
+    pub fn push_str(&mut self, other: &str) {
+        self.bytes.extend_from_slice(other.as_bytes())
+    }
+
+    /// Append a WTF-8 slice at the end of the string.
+    ///
+    /// This replaces newly paired surrogates at the boundary
+    /// with a supplementary code point,
+    /// like concatenating ill-formed UTF-16 strings effectively would.
+    #[inline]
+    pub fn push_wtf8(&mut self, other: &Wtf8) {
+        match ((&*self).final_lead_surrogate(), other.initial_trail_surrogate()) {
+            // Replace newly paired surrogates by a supplementary code point.
+            (Some(lead), Some(trail)) => {
+                let len_without_lead_surrogate = self.len() - 3;
+                self.bytes.truncate(len_without_lead_surrogate);
+                let other_without_trail_surrogate = &other.bytes[3..];
+                // 4 bytes for the supplementary code point
+                self.bytes.reserve(4 + other_without_trail_surrogate.len());
+                self.push_char(decode_surrogate_pair(lead, trail));
+                self.bytes.extend_from_slice(other_without_trail_surrogate);
+            }
+            _ => self.bytes.extend_from_slice(&other.bytes)
+        }
+    }
+
+    /// Append a Unicode scalar value at the end of the string.
+    #[inline]
+    pub fn push_char(&mut self, c: char) {
+        self.push_code_point_unchecked(CodePoint::from_char(c))
+    }
+
+    /// Append a code point at the end of the string.
+    ///
+    /// This replaces newly paired surrogates at the boundary
+    /// with a supplementary code point,
+    /// like concatenating ill-formed UTF-16 strings effectively would.
+    #[inline]
+    pub fn push(&mut self, code_point: CodePoint) {
+        if let trail @ 0xDC00...0xDFFF = code_point.to_u32() {
+            if let Some(lead) = (&*self).final_lead_surrogate() {
+                let len_without_lead_surrogate = self.len() - 3;
+                self.bytes.truncate(len_without_lead_surrogate);
+                self.push_char(decode_surrogate_pair(lead, trail as u16));
+                return
+            }
+        }
+
+        // No newly paired surrogates at the boundary.
+        self.push_code_point_unchecked(code_point)
+    }
+
+    /// Shortens a string to the specified length.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `new_len` > current length,
+    /// or if `new_len` is not a code point boundary.
+    #[inline]
+    pub fn truncate(&mut self, new_len: usize) {
+        assert!(is_code_point_boundary(self, new_len));
+        self.bytes.truncate(new_len)
+    }
+
+    /// Consumes the WTF-8 string and tries to convert it to UTF-8.
+    ///
+    /// This does not copy the data.
+    ///
+    /// If the contents are not well-formed UTF-8
+    /// (that is, if the string contains surrogates),
+    /// the original WTF-8 string is returned instead.
+    pub fn into_string(self) -> Result<String, Wtf8Buf> {
+        match self.next_surrogate(0) {
+            None => Ok(unsafe { String::from_utf8_unchecked(self.bytes) }),
+            Some(_) => Err(self),
+        }
+    }
+
+    /// Consumes the WTF-8 string and converts it lossily to UTF-8.
+    ///
+    /// This does not copy the data (but may overwrite parts of it in place).
+    ///
+    /// Surrogates are replaced with `"\u{FFFD}"` (the replacement character “�”)
+    pub fn into_string_lossy(mut self) -> String {
+        let mut pos = 0;
+        loop {
+            match self.next_surrogate(pos) {
+                Some((surrogate_pos, _)) => {
+                    pos = surrogate_pos + 3;
+                    self.bytes[surrogate_pos..pos]
+                        .copy_from_slice(UTF8_REPLACEMENT_CHARACTER);
+                },
+                None => return unsafe { String::from_utf8_unchecked(self.bytes) }
+            }
+        }
+    }
+}
+
+/// Create a new WTF-8 string from an iterator of code points.
+///
+/// This replaces surrogate code point pairs with supplementary code points,
+/// like concatenating ill-formed UTF-16 strings effectively would.
+impl FromIterator<CodePoint> for Wtf8Buf {
+    fn from_iter<T: IntoIterator<Item=CodePoint>>(iter: T) -> Wtf8Buf {
+        let mut string = Wtf8Buf::new();
+        string.extend(iter);
+        string
+    }
+}
+
+/// Append code points from an iterator to the string.
+///
+/// This replaces surrogate code point pairs with supplementary code points,
+/// like concatenating ill-formed UTF-16 strings effectively would.
+impl Extend<CodePoint> for Wtf8Buf {
+    fn extend<T: IntoIterator<Item=CodePoint>>(&mut self, iter: T) {
+        let iterator = iter.into_iter();
+        let (low, _high) = iterator.size_hint();
+        // Lower bound of one byte per code point (ASCII only)
+        self.bytes.reserve(low);
+        for code_point in iterator {
+            self.push(code_point);
+        }
+    }
+}
+
+/// A borrowed slice of well-formed WTF-8 data.
+///
+/// Similar to `&str`, but can additionally contain surrogate code points
+/// if they’re not in a surrogate pair.
+#[derive(Eq, Ord, PartialEq, PartialOrd)]
+pub struct Wtf8 {
+    bytes: [u8]
+}
+
+impl AsInner<[u8]> for Wtf8 {
+    fn as_inner(&self) -> &[u8] { &self.bytes }
+}
+
+/// Format the slice with double quotes,
+/// and surrogates as `\u` followed by four hexadecimal digits.
+/// Example: `"a\u{D800}"` for a slice with code points [U+0061, U+D800]
+impl fmt::Debug for Wtf8 {
+    fn fmt(&self, formatter: &mut fmt::Formatter) -> fmt::Result {
+        fn write_str_escaped(f: &mut fmt::Formatter, s: &str) -> fmt::Result {
+            use fmt::Write;
+            for c in s.chars().flat_map(|c| c.escape_debug()) {
+                f.write_char(c)?
+            }
+            Ok(())
+        }
+
+        formatter.write_str("\"")?;
+        let mut pos = 0;
+        loop {
+            match self.next_surrogate(pos) {
+                None => break,
+                Some((surrogate_pos, surrogate)) => {
+                    write_str_escaped(
+                        formatter,
+                        unsafe { str::from_utf8_unchecked(
+                            &self.bytes[pos .. surrogate_pos]
+                        )},
+                    )?;
+                    write!(formatter, "\\u{{{:x}}}", surrogate)?;
+                    pos = surrogate_pos + 3;
+                }
+            }
+        }
+        write_str_escaped(
+            formatter,
+            unsafe { str::from_utf8_unchecked(&self.bytes[pos..]) },
+        )?;
+        formatter.write_str("\"")
+    }
+}
+
+impl Wtf8 {
+    /// Creates a WTF-8 slice from a UTF-8 `&str` slice.
+    ///
+    /// Since WTF-8 is a superset of UTF-8, this always succeeds.
+    #[inline]
+    pub fn from_str(value: &str) -> &Wtf8 {
+        unsafe { Wtf8::from_bytes_unchecked(value.as_bytes()) }
+    }
+
+    /// Creates a WTF-8 slice from a WTF-8 byte slice.
+    ///
+    /// Since the byte slice is not checked for valid WTF-8, this functions is
+    /// marked unsafe.
+    #[inline]
+    unsafe fn from_bytes_unchecked(value: &[u8]) -> &Wtf8 {
+        mem::transmute(value)
+    }
+
+    /// Returns the length, in WTF-8 bytes.
+    #[inline]
+    pub fn len(&self) -> usize {
+        self.bytes.len()
+    }
+
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.bytes.is_empty()
+    }
+
+    /// Returns the code point at `position` if it is in the ASCII range,
+    /// or `b'\xFF' otherwise.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `position` is beyond the end of the string.
+    #[inline]
+    pub fn ascii_byte_at(&self, position: usize) -> u8 {
+        match self.bytes[position] {
+            ascii_byte @ 0x00 ... 0x7F => ascii_byte,
+            _ => 0xFF
+        }
+    }
+
+    /// Returns an iterator for the string’s code points.
+    #[inline]
+    pub fn code_points(&self) -> Wtf8CodePoints {
+        Wtf8CodePoints { bytes: self.bytes.iter() }
+    }
+
+    /// Tries to convert the string to UTF-8 and return a `&str` slice.
+    ///
+    /// Returns `None` if the string contains surrogates.
+    ///
+    /// This does not copy the data.
+    #[inline]
+    pub fn as_str(&self) -> Option<&str> {
+        // Well-formed WTF-8 is also well-formed UTF-8
+        // if and only if it contains no surrogate.
+        match self.next_surrogate(0) {
+            None => Some(unsafe { str::from_utf8_unchecked(&self.bytes) }),
+            Some(_) => None,
+        }
+    }
+
+    /// Lossily converts the string to UTF-8.
+    /// Returns a UTF-8 `&str` slice if the contents are well-formed in UTF-8.
+    ///
+    /// Surrogates are replaced with `"\u{FFFD}"` (the replacement character “�”).
+    ///
+    /// This only copies the data if necessary (if it contains any surrogate).
+    pub fn to_string_lossy(&self) -> Cow<str> {
+        let surrogate_pos = match self.next_surrogate(0) {
+            None => return Cow::Borrowed(unsafe { str::from_utf8_unchecked(&self.bytes) }),
+            Some((pos, _)) => pos,
+        };
+        let wtf8_bytes = &self.bytes;
+        let mut utf8_bytes = Vec::with_capacity(self.len());
+        utf8_bytes.extend_from_slice(&wtf8_bytes[..surrogate_pos]);
+        utf8_bytes.extend_from_slice(UTF8_REPLACEMENT_CHARACTER);
+        let mut pos = surrogate_pos + 3;
+        loop {
+            match self.next_surrogate(pos) {
+                Some((surrogate_pos, _)) => {
+                    utf8_bytes.extend_from_slice(&wtf8_bytes[pos .. surrogate_pos]);
+                    utf8_bytes.extend_from_slice(UTF8_REPLACEMENT_CHARACTER);
+                    pos = surrogate_pos + 3;
+                },
+                None => {
+                    utf8_bytes.extend_from_slice(&wtf8_bytes[pos..]);
+                    return Cow::Owned(unsafe { String::from_utf8_unchecked(utf8_bytes) })
+                }
+            }
+        }
+    }
+
+    /// Converts the WTF-8 string to potentially ill-formed UTF-16
+    /// and return an iterator of 16-bit code units.
+    ///
+    /// This is lossless:
+    /// calling `Wtf8Buf::from_ill_formed_utf16` on the resulting code units
+    /// would always return the original WTF-8 string.
+    #[inline]
+    pub fn encode_wide(&self) -> EncodeWide {
+        EncodeWide { code_points: self.code_points(), extra: 0 }
+    }
+
+    #[inline]
+    fn next_surrogate(&self, mut pos: usize) -> Option<(usize, u16)> {
+        let mut iter = self.bytes[pos..].iter();
+        loop {
+            let b = match iter.next() {
+                None => return None,
+                Some(&b) => b,
+            };
+            if b < 0x80 {
+                pos += 1;
+            } else if b < 0xE0 {
+                iter.next();
+                pos += 2;
+            } else if b == 0xED {
+                match (iter.next(), iter.next()) {
+                    (Some(&b2), Some(&b3)) if b2 >= 0xA0 => {
+                        return Some((pos, decode_surrogate(b2, b3)))
+                    }
+                    _ => pos += 3
+                }
+            } else if b < 0xF0 {
+                iter.next();
+                iter.next();
+                pos += 3;
+            } else {
+                iter.next();
+                iter.next();
+                iter.next();
+                pos += 4;
+            }
+        }
+    }
+
+    #[inline]
+    fn final_lead_surrogate(&self) -> Option<u16> {
+        let len = self.len();
+        if len < 3 {
+            return None
+        }
+        match &self.bytes[(len - 3)..] {
+            &[0xED, b2 @ 0xA0...0xAF, b3] => Some(decode_surrogate(b2, b3)),
+            _ => None
+        }
+    }
+
+    #[inline]
+    fn initial_trail_surrogate(&self) -> Option<u16> {
+        let len = self.len();
+        if len < 3 {
+            return None
+        }
+        match &self.bytes[..3] {
+            &[0xED, b2 @ 0xB0...0xBF, b3] => Some(decode_surrogate(b2, b3)),
+            _ => None
+        }
+    }
+}
+
+
+/// Return a slice of the given string for the byte range [`begin`..`end`).
+///
+/// # Panics
+///
+/// Panics when `begin` and `end` do not point to code point boundaries,
+/// or point beyond the end of the string.
+impl ops::Index<ops::Range<usize>> for Wtf8 {
+    type Output = Wtf8;
+
+    #[inline]
+    fn index(&self, range: ops::Range<usize>) -> &Wtf8 {
+        // is_code_point_boundary checks that the index is in [0, .len()]
+        if range.start <= range.end &&
+           is_code_point_boundary(self, range.start) &&
+           is_code_point_boundary(self, range.end) {
+            unsafe { slice_unchecked(self, range.start, range.end) }
+        } else {
+            slice_error_fail(self, range.start, range.end)
+        }
+    }
+}
+
+/// Return a slice of the given string from byte `begin` to its end.
+///
+/// # Panics
+///
+/// Panics when `begin` is not at a code point boundary,
+/// or is beyond the end of the string.
+impl ops::Index<ops::RangeFrom<usize>> for Wtf8 {
+    type Output = Wtf8;
+
+    #[inline]
+    fn index(&self, range: ops::RangeFrom<usize>) -> &Wtf8 {
+        // is_code_point_boundary checks that the index is in [0, .len()]
+        if is_code_point_boundary(self, range.start) {
+            unsafe { slice_unchecked(self, range.start, self.len()) }
+        } else {
+            slice_error_fail(self, range.start, self.len())
+        }
+    }
+}
+
+/// Return a slice of the given string from its beginning to byte `end`.
+///
+/// # Panics
+///
+/// Panics when `end` is not at a code point boundary,
+/// or is beyond the end of the string.
+impl ops::Index<ops::RangeTo<usize>> for Wtf8 {
+    type Output = Wtf8;
+
+    #[inline]
+    fn index(&self, range: ops::RangeTo<usize>) -> &Wtf8 {
+        // is_code_point_boundary checks that the index is in [0, .len()]
+        if is_code_point_boundary(self, range.end) {
+            unsafe { slice_unchecked(self, 0, range.end) }
+        } else {
+            slice_error_fail(self, 0, range.end)
+        }
+    }
+}
+
+impl ops::Index<ops::RangeFull> for Wtf8 {
+    type Output = Wtf8;
+
+    #[inline]
+    fn index(&self, _range: ops::RangeFull) -> &Wtf8 {
+        self
+    }
+}
+
+#[inline]
+fn decode_surrogate(second_byte: u8, third_byte: u8) -> u16 {
+    // The first byte is assumed to be 0xED
+    0xD800 | (second_byte as u16 & 0x3F) << 6 | third_byte as u16 & 0x3F
+}
+
+#[inline]
+fn decode_surrogate_pair(lead: u16, trail: u16) -> char {
+    let code_point = 0x10000 + ((((lead - 0xD800) as u32) << 10) | (trail - 0xDC00) as u32);
+    unsafe { char::from_u32_unchecked(code_point) }
+}
+
+/// Copied from core::str::StrPrelude::is_char_boundary
+#[inline]
+pub fn is_code_point_boundary(slice: &Wtf8, index: usize) -> bool {
+    if index == slice.len() { return true; }
+    match slice.bytes.get(index) {
+        None => false,
+        Some(&b) => b < 128 || b >= 192,
+    }
+}
+
+/// Copied from core::str::raw::slice_unchecked
+#[inline]
+pub unsafe fn slice_unchecked(s: &Wtf8, begin: usize, end: usize) -> &Wtf8 {
+    // memory layout of an &[u8] and &Wtf8 are the same
+    Wtf8::from_bytes_unchecked(slice::from_raw_parts(
+        s.bytes.as_ptr().offset(begin as isize),
+        end - begin
+    ))
+}
+
+/// Copied from core::str::raw::slice_error_fail
+#[inline(never)]
+pub fn slice_error_fail(s: &Wtf8, begin: usize, end: usize) -> ! {
+    assert!(begin <= end);
+    panic!("index {} and/or {} in `{:?}` do not lie on character boundary",
+          begin, end, s);
+}
+
+/// Iterator for the code points of a WTF-8 string.
+///
+/// Created with the method `.code_points()`.
+#[derive(Clone)]
+pub struct Wtf8CodePoints<'a> {
+    bytes: slice::Iter<'a, u8>
+}
+
+impl<'a> Iterator for Wtf8CodePoints<'a> {
+    type Item = CodePoint;
+
+    #[inline]
+    fn next(&mut self) -> Option<CodePoint> {
+        next_code_point(&mut self.bytes).map(|c| CodePoint { value: c })
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let len = self.bytes.len();
+        (len.saturating_add(3) / 4, Some(len))
+    }
+}
+
+#[stable(feature = "rust1", since = "1.0.0")]
+#[derive(Clone)]
+pub struct EncodeWide<'a> {
+    code_points: Wtf8CodePoints<'a>,
+    extra: u16
+}
+
+// Copied from libunicode/u_str.rs
+#[stable(feature = "rust1", since = "1.0.0")]
+impl<'a> Iterator for EncodeWide<'a> {
+    type Item = u16;
+
+    #[inline]
+    fn next(&mut self) -> Option<u16> {
+        if self.extra != 0 {
+            let tmp = self.extra;
+            self.extra = 0;
+            return Some(tmp);
+        }
+
+        let mut buf = [0; 2];
+        self.code_points.next().map(|code_point| {
+            let c = unsafe {
+                char::from_u32_unchecked(code_point.value)
+            };
+            let n = c.encode_utf16(&mut buf).len();
+            if n == 2 {
+                self.extra = buf[1];
+            }
+            buf[0]
+        })
+    }
+
+    #[inline]
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        let (low, high) = self.code_points.size_hint();
+        // every code point gets either one u16 or two u16,
+        // so this iterator is between 1 or 2 times as
+        // long as the underlying iterator.
+        (low, high.and_then(|n| n.checked_mul(2)))
+    }
+}
+
+impl Hash for CodePoint {
+    #[inline]
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        self.value.hash(state)
+    }
+}
+
+impl Hash for Wtf8Buf {
+    #[inline]
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        state.write(&self.bytes);
+        0xfeu8.hash(state)
+    }
+}
+
+impl Hash for Wtf8 {
+    #[inline]
+    fn hash<H: Hasher>(&self, state: &mut H) {
+        state.write(&self.bytes);
+        0xfeu8.hash(state)
+    }
+}
+
+impl AsciiExt for Wtf8 {
+    type Owned = Wtf8Buf;
+
+    fn is_ascii(&self) -> bool {
+        self.bytes.is_ascii()
+    }
+    fn to_ascii_uppercase(&self) -> Wtf8Buf {
+        Wtf8Buf { bytes: self.bytes.to_ascii_uppercase() }
+    }
+    fn to_ascii_lowercase(&self) -> Wtf8Buf {
+        Wtf8Buf { bytes: self.bytes.to_ascii_lowercase() }
+    }
+    fn eq_ignore_ascii_case(&self, other: &Wtf8) -> bool {
+        self.bytes.eq_ignore_ascii_case(&other.bytes)
+    }
+
+    fn make_ascii_uppercase(&mut self) { self.bytes.make_ascii_uppercase() }
+    fn make_ascii_lowercase(&mut self) { self.bytes.make_ascii_lowercase() }
+}
+
+#[cfg(test)]
+mod tests {
+    use borrow::Cow;
+    use super::*;
+
+    #[test]
+    fn code_point_from_u32() {
+        assert!(CodePoint::from_u32(0).is_some());
+        assert!(CodePoint::from_u32(0xD800).is_some());
+        assert!(CodePoint::from_u32(0x10FFFF).is_some());
+        assert!(CodePoint::from_u32(0x110000).is_none());
+    }
+
+    #[test]
+    fn code_point_to_u32() {
+        fn c(value: u32) -> CodePoint { CodePoint::from_u32(value).unwrap() }
+        assert_eq!(c(0).to_u32(), 0);
+        assert_eq!(c(0xD800).to_u32(), 0xD800);
+        assert_eq!(c(0x10FFFF).to_u32(), 0x10FFFF);
+    }
+
+    #[test]
+    fn code_point_from_char() {
+        assert_eq!(CodePoint::from_char('a').to_u32(), 0x61);
+        assert_eq!(CodePoint::from_char('💩').to_u32(), 0x1F4A9);
+    }
+
+    #[test]
+    fn code_point_to_string() {
+        assert_eq!(format!("{:?}", CodePoint::from_char('a')), "U+0061");
+        assert_eq!(format!("{:?}", CodePoint::from_char('💩')), "U+1F4A9");
+    }
+
+    #[test]
+    fn code_point_to_char() {
+        fn c(value: u32) -> CodePoint { CodePoint::from_u32(value).unwrap() }
+        assert_eq!(c(0x61).to_char(), Some('a'));
+        assert_eq!(c(0x1F4A9).to_char(), Some('💩'));
+        assert_eq!(c(0xD800).to_char(), None);
+    }
+
+    #[test]
+    fn code_point_to_char_lossy() {
+        fn c(value: u32) -> CodePoint { CodePoint::from_u32(value).unwrap() }
+        assert_eq!(c(0x61).to_char_lossy(), 'a');
+        assert_eq!(c(0x1F4A9).to_char_lossy(), '💩');
+        assert_eq!(c(0xD800).to_char_lossy(), '\u{FFFD}');
+    }
+
+    #[test]
+    fn wtf8buf_new() {
+        assert_eq!(Wtf8Buf::new().bytes, b"");
+    }
+
+    #[test]
+    fn wtf8buf_from_str() {
+        assert_eq!(Wtf8Buf::from_str("").bytes, b"");
+        assert_eq!(Wtf8Buf::from_str("aé 💩").bytes,
+                   b"a\xC3\xA9 \xF0\x9F\x92\xA9");
+    }
+
+    #[test]
+    fn wtf8buf_from_string() {
+        assert_eq!(Wtf8Buf::from_string(String::from("")).bytes, b"");
+        assert_eq!(Wtf8Buf::from_string(String::from("aé 💩")).bytes,
+                   b"a\xC3\xA9 \xF0\x9F\x92\xA9");
+    }
+
+    #[test]
+    fn wtf8buf_from_wide() {
+        assert_eq!(Wtf8Buf::from_wide(&[]).bytes, b"");
+        assert_eq!(Wtf8Buf::from_wide(
+                      &[0x61, 0xE9, 0x20, 0xD83D, 0xD83D, 0xDCA9]).bytes,
+                   b"a\xC3\xA9 \xED\xA0\xBD\xF0\x9F\x92\xA9");
+    }
+
+    #[test]
+    fn wtf8buf_push_str() {
+        let mut string = Wtf8Buf::new();
+        assert_eq!(string.bytes, b"");
+        string.push_str("aé 💩");
+        assert_eq!(string.bytes, b"a\xC3\xA9 \xF0\x9F\x92\xA9");
+    }
+
+    #[test]
+    fn wtf8buf_push_char() {
+        let mut string = Wtf8Buf::from_str("aé ");
+        assert_eq!(string.bytes, b"a\xC3\xA9 ");
+        string.push_char('💩');
+        assert_eq!(string.bytes, b"a\xC3\xA9 \xF0\x9F\x92\xA9");
+    }
+
+    #[test]
+    fn wtf8buf_push() {
+        let mut string = Wtf8Buf::from_str("aé ");
+        assert_eq!(string.bytes, b"a\xC3\xA9 ");
+        string.push(CodePoint::from_char('💩'));
+        assert_eq!(string.bytes, b"a\xC3\xA9 \xF0\x9F\x92\xA9");
+
+        fn c(value: u32) -> CodePoint { CodePoint::from_u32(value).unwrap() }
+
+        let mut string = Wtf8Buf::new();
+        string.push(c(0xD83D));  // lead
+        string.push(c(0xDCA9));  // trail
+        assert_eq!(string.bytes, b"\xF0\x9F\x92\xA9");  // Magic!
+
+        let mut string = Wtf8Buf::new();
+        string.push(c(0xD83D));  // lead
+        string.push(c(0x20));  // not surrogate
+        string.push(c(0xDCA9));  // trail
+        assert_eq!(string.bytes, b"\xED\xA0\xBD \xED\xB2\xA9");
+
+        let mut string = Wtf8Buf::new();
+        string.push(c(0xD800));  // lead
+        string.push(c(0xDBFF));  // lead
+        assert_eq!(string.bytes, b"\xED\xA0\x80\xED\xAF\xBF");
+
+        let mut string = Wtf8Buf::new();
+        string.push(c(0xD800));  // lead
+        string.push(c(0xE000));  // not surrogate
+        assert_eq!(string.bytes, b"\xED\xA0\x80\xEE\x80\x80");
+
+        let mut string = Wtf8Buf::new();
+        string.push(c(0xD7FF));  // not surrogate
+        string.push(c(0xDC00));  // trail
+        assert_eq!(string.bytes, b"\xED\x9F\xBF\xED\xB0\x80");
+
+        let mut string = Wtf8Buf::new();
+        string.push(c(0x61));  // not surrogate, < 3 bytes
+        string.push(c(0xDC00));  // trail
+        assert_eq!(string.bytes, b"\x61\xED\xB0\x80");
+
+        let mut string = Wtf8Buf::new();
+        string.push(c(0xDC00));  // trail
+        assert_eq!(string.bytes, b"\xED\xB0\x80");
+    }
+
+    #[test]
+    fn wtf8buf_push_wtf8() {
+        let mut string = Wtf8Buf::from_str("aé");
+        assert_eq!(string.bytes, b"a\xC3\xA9");
+        string.push_wtf8(Wtf8::from_str(" 💩"));
+        assert_eq!(string.bytes, b"a\xC3\xA9 \xF0\x9F\x92\xA9");
+
+        fn w(v: &[u8]) -> &Wtf8 { unsafe { Wtf8::from_bytes_unchecked(v) } }
+
+        let mut string = Wtf8Buf::new();
+        string.push_wtf8(w(b"\xED\xA0\xBD"));  // lead
+        string.push_wtf8(w(b"\xED\xB2\xA9"));  // trail
+        assert_eq!(string.bytes, b"\xF0\x9F\x92\xA9");  // Magic!
+
+        let mut string = Wtf8Buf::new();
+        string.push_wtf8(w(b"\xED\xA0\xBD"));  // lead
+        string.push_wtf8(w(b" "));  // not surrogate
+        string.push_wtf8(w(b"\xED\xB2\xA9"));  // trail
+        assert_eq!(string.bytes, b"\xED\xA0\xBD \xED\xB2\xA9");
+
+        let mut string = Wtf8Buf::new();
+        string.push_wtf8(w(b"\xED\xA0\x80"));  // lead
+        string.push_wtf8(w(b"\xED\xAF\xBF"));  // lead
+        assert_eq!(string.bytes, b"\xED\xA0\x80\xED\xAF\xBF");
+
+        let mut string = Wtf8Buf::new();
+        string.push_wtf8(w(b"\xED\xA0\x80"));  // lead
+        string.push_wtf8(w(b"\xEE\x80\x80"));  // not surrogate
+        assert_eq!(string.bytes, b"\xED\xA0\x80\xEE\x80\x80");
+
+        let mut string = Wtf8Buf::new();
+        string.push_wtf8(w(b"\xED\x9F\xBF"));  // not surrogate
+        string.push_wtf8(w(b"\xED\xB0\x80"));  // trail
+        assert_eq!(string.bytes, b"\xED\x9F\xBF\xED\xB0\x80");
+
+        let mut string = Wtf8Buf::new();
+        string.push_wtf8(w(b"a"));  // not surrogate, < 3 bytes
+        string.push_wtf8(w(b"\xED\xB0\x80"));  // trail
+        assert_eq!(string.bytes, b"\x61\xED\xB0\x80");
+
+        let mut string = Wtf8Buf::new();
+        string.push_wtf8(w(b"\xED\xB0\x80"));  // trail
+        assert_eq!(string.bytes, b"\xED\xB0\x80");
+    }
+
+    #[test]
+    fn wtf8buf_truncate() {
+        let mut string = Wtf8Buf::from_str("aé");
+        string.truncate(1);
+        assert_eq!(string.bytes, b"a");
+    }
+
+    #[test]
+    #[should_panic]
+    fn wtf8buf_truncate_fail_code_point_boundary() {
+        let mut string = Wtf8Buf::from_str("aé");
+        string.truncate(2);
+    }
+
+    #[test]
+    #[should_panic]
+    fn wtf8buf_truncate_fail_longer() {
+        let mut string = Wtf8Buf::from_str("aé");
+        string.truncate(4);
+    }
+
+    #[test]
+    fn wtf8buf_into_string() {
+        let mut string = Wtf8Buf::from_str("aé 💩");
+        assert_eq!(string.clone().into_string(), Ok(String::from("aé 💩")));
+        string.push(CodePoint::from_u32(0xD800).unwrap());
+        assert_eq!(string.clone().into_string(), Err(string));
+    }
+
+    #[test]
+    fn wtf8buf_into_string_lossy() {
+        let mut string = Wtf8Buf::from_str("aé 💩");
+        assert_eq!(string.clone().into_string_lossy(), String::from("aé 💩"));
+        string.push(CodePoint::from_u32(0xD800).unwrap());
+        assert_eq!(string.clone().into_string_lossy(), String::from("aé 💩�"));
+    }
+
+    #[test]
+    fn wtf8buf_from_iterator() {
+        fn f(values: &[u32]) -> Wtf8Buf {
+            values.iter().map(|&c| CodePoint::from_u32(c).unwrap()).collect::<Wtf8Buf>()
+        }
+        assert_eq!(f(&[0x61, 0xE9, 0x20, 0x1F4A9]).bytes, b"a\xC3\xA9 \xF0\x9F\x92\xA9");
+
+        assert_eq!(f(&[0xD83D, 0xDCA9]).bytes, b"\xF0\x9F\x92\xA9");  // Magic!
+        assert_eq!(f(&[0xD83D, 0x20, 0xDCA9]).bytes, b"\xED\xA0\xBD \xED\xB2\xA9");
+        assert_eq!(f(&[0xD800, 0xDBFF]).bytes, b"\xED\xA0\x80\xED\xAF\xBF");
+        assert_eq!(f(&[0xD800, 0xE000]).bytes, b"\xED\xA0\x80\xEE\x80\x80");
+        assert_eq!(f(&[0xD7FF, 0xDC00]).bytes, b"\xED\x9F\xBF\xED\xB0\x80");
+        assert_eq!(f(&[0x61, 0xDC00]).bytes, b"\x61\xED\xB0\x80");
+        assert_eq!(f(&[0xDC00]).bytes, b"\xED\xB0\x80");
+    }
+
+    #[test]
+    fn wtf8buf_extend() {
+        fn e(initial: &[u32], extended: &[u32]) -> Wtf8Buf {
+            fn c(value: &u32) -> CodePoint { CodePoint::from_u32(*value).unwrap() }
+            let mut string = initial.iter().map(c).collect::<Wtf8Buf>();
+            string.extend(extended.iter().map(c));
+            string
+        }
+
+        assert_eq!(e(&[0x61, 0xE9], &[0x20, 0x1F4A9]).bytes,
+                   b"a\xC3\xA9 \xF0\x9F\x92\xA9");
+
+        assert_eq!(e(&[0xD83D], &[0xDCA9]).bytes, b"\xF0\x9F\x92\xA9");  // Magic!
+        assert_eq!(e(&[0xD83D, 0x20], &[0xDCA9]).bytes, b"\xED\xA0\xBD \xED\xB2\xA9");
+        assert_eq!(e(&[0xD800], &[0xDBFF]).bytes, b"\xED\xA0\x80\xED\xAF\xBF");
+        assert_eq!(e(&[0xD800], &[0xE000]).bytes, b"\xED\xA0\x80\xEE\x80\x80");
+        assert_eq!(e(&[0xD7FF], &[0xDC00]).bytes, b"\xED\x9F\xBF\xED\xB0\x80");
+        assert_eq!(e(&[0x61], &[0xDC00]).bytes, b"\x61\xED\xB0\x80");
+        assert_eq!(e(&[], &[0xDC00]).bytes, b"\xED\xB0\x80");
+    }
+
+    #[test]
+    fn wtf8buf_show() {
+        let mut string = Wtf8Buf::from_str("a\té \u{7f}💩\r");
+        string.push(CodePoint::from_u32(0xD800).unwrap());
+        assert_eq!(format!("{:?}", string), "\"a\\té \\u{7f}\u{1f4a9}\\r\\u{d800}\"");
+    }
+
+    #[test]
+    fn wtf8buf_as_slice() {
+        assert_eq!(Wtf8Buf::from_str("aé").as_slice(), Wtf8::from_str("aé"));
+    }
+
+    #[test]
+    fn wtf8buf_show_str() {
+        let text = "a\té 💩\r";
+        let string = Wtf8Buf::from_str(text);
+        assert_eq!(format!("{:?}", text), format!("{:?}", string));
+    }
+
+    #[test]
+    fn wtf8_from_str() {
+        assert_eq!(&Wtf8::from_str("").bytes, b"");
+        assert_eq!(&Wtf8::from_str("aé 💩").bytes, b"a\xC3\xA9 \xF0\x9F\x92\xA9");
+    }
+
+    #[test]
+    fn wtf8_len() {
+        assert_eq!(Wtf8::from_str("").len(), 0);
+        assert_eq!(Wtf8::from_str("aé 💩").len(), 8);
+    }
+
+    #[test]
+    fn wtf8_slice() {
+        assert_eq!(&Wtf8::from_str("aé 💩")[1.. 4].bytes, b"\xC3\xA9 ");
+    }
+
+    #[test]
+    #[should_panic]
+    fn wtf8_slice_not_code_point_boundary() {
+        &Wtf8::from_str("aé 💩")[2.. 4];
+    }
+
+    #[test]
+    fn wtf8_slice_from() {
+        assert_eq!(&Wtf8::from_str("aé 💩")[1..].bytes, b"\xC3\xA9 \xF0\x9F\x92\xA9");
+    }
+
+    #[test]
+    #[should_panic]
+    fn wtf8_slice_from_not_code_point_boundary() {
+        &Wtf8::from_str("aé 💩")[2..];
+    }
+
+    #[test]
+    fn wtf8_slice_to() {
+        assert_eq!(&Wtf8::from_str("aé 💩")[..4].bytes, b"a\xC3\xA9 ");
+    }
+
+    #[test]
+    #[should_panic]
+    fn wtf8_slice_to_not_code_point_boundary() {
+        &Wtf8::from_str("aé 💩")[5..];
+    }
+
+    #[test]
+    fn wtf8_ascii_byte_at() {
+        let slice = Wtf8::from_str("aé 💩");
+        assert_eq!(slice.ascii_byte_at(0), b'a');
+        assert_eq!(slice.ascii_byte_at(1), b'\xFF');
+        assert_eq!(slice.ascii_byte_at(2), b'\xFF');
+        assert_eq!(slice.ascii_byte_at(3), b' ');
+        assert_eq!(slice.ascii_byte_at(4), b'\xFF');
+    }
+
+    #[test]
+    fn wtf8_code_points() {
+        fn c(value: u32) -> CodePoint { CodePoint::from_u32(value).unwrap() }
+        fn cp(string: &Wtf8Buf) -> Vec<Option<char>> {
+            string.code_points().map(|c| c.to_char()).collect::<Vec<_>>()
+        }
+        let mut string = Wtf8Buf::from_str("é ");
+        assert_eq!(cp(&string), [Some('é'), Some(' ')]);
+        string.push(c(0xD83D));
+        assert_eq!(cp(&string), [Some('é'), Some(' '), None]);
+        string.push(c(0xDCA9));
+        assert_eq!(cp(&string), [Some('é'), Some(' '), Some('💩')]);
+    }
+
+    #[test]
+    fn wtf8_as_str() {
+        assert_eq!(Wtf8::from_str("").as_str(), Some(""));
+        assert_eq!(Wtf8::from_str("aé 💩").as_str(), Some("aé 💩"));
+        let mut string = Wtf8Buf::new();
+        string.push(CodePoint::from_u32(0xD800).unwrap());
+        assert_eq!(string.as_str(), None);
+    }
+
+    #[test]
+    fn wtf8_to_string_lossy() {
+        assert_eq!(Wtf8::from_str("").to_string_lossy(), Cow::Borrowed(""));
+        assert_eq!(Wtf8::from_str("aé 💩").to_string_lossy(), Cow::Borrowed("aé 💩"));
+        let mut string = Wtf8Buf::from_str("aé 💩");
+        string.push(CodePoint::from_u32(0xD800).unwrap());
+        let expected: Cow<str> = Cow::Owned(String::from("aé 💩�"));
+        assert_eq!(string.to_string_lossy(), expected);
+    }
+
+    #[test]
+    fn wtf8_encode_wide() {
+        let mut string = Wtf8Buf::from_str("aé ");
+        string.push(CodePoint::from_u32(0xD83D).unwrap());
+        string.push_char('💩');
+        assert_eq!(string.encode_wide().collect::<Vec<_>>(),
+                   vec![0x61, 0xE9, 0x20, 0xD83D, 0xD83D, 0xDCA9]);
+    }
+}