std: Redesign c_str and c_vec

This commit is an implementation of [RFC 494][rfc] which removes the entire
`std::c_vec` module and redesigns the `std::c_str` module as `std::ffi`.

[rfc]: https://github.com/rust-lang/rfcs/blob/master/text/0494-c_str-and-c_vec-stability.md

The interface of the new `CString` is outlined in the linked RFC, the primary
changes being:

* The `ToCStr` trait is gone, meaning the `with_c_str` and `to_c_str` methods
  are now gone. These two methods are replaced with a `CString::from_slice`
  method.
* The `CString` type is now just a wrapper around `Vec<u8>` with a static
  guarantee that there is a trailing nul byte with no internal nul bytes. This
  means that `CString` now implements `Deref<Target = [c_char]>`, which is where
  it gains most of its methods from. A few helper methods are added to acquire a
  slice of `u8` instead of `c_char`, as well as including a slice with the
  trailing nul byte if necessary.
* All usage of non-owned `CString` values is now done via two functions inside
  of `std::ffi`, called `c_str_to_bytes` and `c_str_to_bytes_with_nul`. These
  functions are now the one method used to convert a `*const c_char` to a Rust
  slice of `u8`.

Many more details, including newly deprecated methods, can be found linked in
the RFC. This is a:

[breaking-change]
Closes #20444

2 files changed, 8 insertions, 6 deletions

diff --git a/src/libstd/sys/common/mod.rs b/src/libstd/sys/common/mod.rs
index a441e55a732..a31dcc9884f 100644
--- a/src/libstd/sys/common/mod.rs
+++ b/src/libstd/sys/common/mod.rs
@@ -14,7 +14,7 @@
 use io::{self, IoError, IoResult};
 use prelude::v1::*;
 use sys::{last_error, retry};
-use c_str::CString;
+use ffi::CString;
 use num::Int;
 use path::BytesContainer;
 use collections;
diff --git a/src/libstd/sys/common/net.rs b/src/libstd/sys/common/net.rs
index 3f67b284f68..4cf891ac498 100644
--- a/src/libstd/sys/common/net.rs
+++ b/src/libstd/sys/common/net.rs
@@ -12,15 +12,16 @@ use prelude::v1::*;
 use self::SocketStatus::*;
 use self::InAddr::*;
 
-use c_str::ToCStr;
+use ffi::CString;
+use ffi;
 use io::net::addrinfo;
 use io::net::ip::{SocketAddr, IpAddr, Ipv4Addr, Ipv6Addr};
 use io::{IoResult, IoError};
 use libc::{self, c_char, c_int};
-use c_str::CString;
 use mem;
 use num::Int;
 use ptr::{self, null, null_mut};
+use str;
 use sys::{self, retry, c, sock_t, last_error, last_net_error, last_gai_error, close_sock,
           wrlen, msglen_t, os, wouldblock, set_nonblocking, timer, ms_to_timeval,
           decode_error_detailed};
@@ -234,9 +235,9 @@ pub fn get_host_addresses(host: Option<&str>, servname: Option<&str>,
 
     assert!(host.is_some() || servname.is_some());
 
-    let c_host = host.map(|x| x.to_c_str());
+    let c_host = host.map(|x| CString::from_slice(x.as_bytes()));
     let c_host = c_host.as_ref().map(|x| x.as_ptr()).unwrap_or(null());
-    let c_serv = servname.map(|x| x.to_c_str());
+    let c_serv = servname.map(|x| CString::from_slice(x.as_bytes()));
     let c_serv = c_serv.as_ref().map(|x| x.as_ptr()).unwrap_or(null());
 
     let hint = hint.map(|hint| {
@@ -324,7 +325,8 @@ pub fn get_address_name(addr: IpAddr) -> Result<String, IoError> {
     }
 
     unsafe {
-        Ok(CString::new(hostbuf.as_ptr(), false).as_str().unwrap().to_string())
+        Ok(str::from_utf8(ffi::c_str_to_bytes(&hostbuf.as_ptr()))
+               .unwrap().to_string())
     }
 }