diff options
Diffstat (limited to 'src/libstd')
| -rw-r--r-- | src/libstd/ffi/c_str.rs | 3 | ||||
| -rw-r--r-- | src/libstd/io/buffered.rs | 3 | ||||
| -rw-r--r-- | src/libstd/io/mod.rs | 3 | ||||
| -rw-r--r-- | src/libstd/lib.rs | 2 | ||||
| -rw-r--r-- | src/libstd/memchr.rs | 386 | ||||
| -rw-r--r-- | src/libstd/sys/unix/os.rs | 3 |
6 files changed, 396 insertions, 4 deletions
diff --git a/src/libstd/ffi/c_str.rs b/src/libstd/ffi/c_str.rs index 318ff410cba..3f3913471b8 100644 --- a/src/libstd/ffi/c_str.rs +++ b/src/libstd/ffi/c_str.rs @@ -19,6 +19,7 @@ use io; use iter::Iterator; use libc; use mem; +use memchr; use ops::Deref; use option::Option::{self, Some, None}; use os::raw::c_char; @@ -188,7 +189,7 @@ impl CString { } fn _new(bytes: Vec<u8>) -> Result<CString, NulError> { - match bytes.iter().position(|x| *x == 0) { + match memchr::memchr(0, &bytes) { Some(i) => Err(NulError(i, bytes)), None => Ok(unsafe { CString::from_vec_unchecked(bytes) }), } diff --git a/src/libstd/io/buffered.rs b/src/libstd/io/buffered.rs index 90a79da3483..79eedbeda2c 100644 --- a/src/libstd/io/buffered.rs +++ b/src/libstd/io/buffered.rs @@ -18,6 +18,7 @@ use cmp; use error; use fmt; use io::{self, DEFAULT_BUF_SIZE, Error, ErrorKind, SeekFrom}; +use memchr; /// The `BufReader` struct adds buffering to any reader. /// @@ -746,7 +747,7 @@ impl<W: Write> LineWriter<W> { #[stable(feature = "rust1", since = "1.0.0")] impl<W: Write> Write for LineWriter<W> { fn write(&mut self, buf: &[u8]) -> io::Result<usize> { - match buf.iter().rposition(|b| *b == b'\n') { + match memchr::memrchr(b'\n', buf) { Some(i) => { let n = try!(self.inner.write(&buf[..i + 1])); if n != i + 1 { return Ok(n) } diff --git a/src/libstd/io/mod.rs b/src/libstd/io/mod.rs index efe40cf07c1..cc3f8097a88 100644 --- a/src/libstd/io/mod.rs +++ b/src/libstd/io/mod.rs @@ -254,6 +254,7 @@ use result; use string::String; use str; use vec::Vec; +use memchr; #[stable(feature = "rust1", since = "1.0.0")] pub use self::buffered::{BufReader, BufWriter, LineWriter}; @@ -1194,7 +1195,7 @@ fn read_until<R: BufRead + ?Sized>(r: &mut R, delim: u8, buf: &mut Vec<u8>) Err(ref e) if e.kind() == ErrorKind::Interrupted => continue, Err(e) => return Err(e) }; - match available.iter().position(|x| *x == delim) { + match memchr::memchr(delim, available) { Some(i) => { buf.extend_from_slice(&available[..i + 1]); (true, i + 1) diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs index 0f8b2f6e17b..eba0c799cd2 100644 --- a/src/libstd/lib.rs +++ b/src/libstd/lib.rs @@ -248,6 +248,7 @@ #![feature(link_args)] #![feature(linkage)] #![feature(macro_reexport)] +#![feature(num_bits_bytes)] #![feature(on_unimplemented)] #![feature(oom)] #![feature(optin_builtin_traits)] @@ -429,6 +430,7 @@ pub mod path; pub mod process; pub mod sync; pub mod time; +mod memchr; #[macro_use] #[path = "sys/common/mod.rs"] mod sys_common; diff --git a/src/libstd/memchr.rs b/src/libstd/memchr.rs new file mode 100644 index 00000000000..c654efd499b --- /dev/null +++ b/src/libstd/memchr.rs @@ -0,0 +1,386 @@ +// 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 + + + +/// A safe interface to `memchr`. +/// +/// Returns the index corresponding to the first occurrence of `needle` in +/// `haystack`, or `None` if one is not found. +/// +/// memchr reduces to super-optimized machine code at around an order of +/// magnitude faster than `haystack.iter().position(|&b| b == needle)`. +/// (See benchmarks.) +/// +/// # Example +/// +/// This shows how to find the first position of a byte in a byte string. +/// +/// ```rust,ignore +/// use memchr::memchr; +/// +/// let haystack = b"the quick brown fox"; +/// assert_eq!(memchr(b'k', haystack), Some(8)); +/// ``` +pub fn memchr(needle: u8, haystack: &[u8]) -> Option<usize> { + // libc memchr + #[cfg(not(target_os = "windows"))] + fn memchr_specific(needle: u8, haystack: &[u8]) -> Option<usize> { + use libc; + + let p = unsafe { + libc::memchr( + haystack.as_ptr() as *const libc::c_void, + needle as libc::c_int, + haystack.len() as libc::size_t) + }; + if p.is_null() { + None + } else { + Some(p as usize - (haystack.as_ptr() as usize)) + } + } + + // use fallback on windows, since it's faster + #[cfg(target_os = "windows")] + fn memchr_specific(needle: u8, haystack: &[u8]) -> Option<usize> { + fallback::memchr(needle, haystack) + } + + memchr_specific(needle, haystack) +} + +/// A safe interface to `memrchr`. +/// +/// Returns the index corresponding to the last occurrence of `needle` in +/// `haystack`, or `None` if one is not found. +/// +/// # Example +/// +/// This shows how to find the last position of a byte in a byte string. +/// +/// ```rust,ignore +/// use memchr::memrchr; +/// +/// let haystack = b"the quick brown fox"; +/// assert_eq!(memrchr(b'o', haystack), Some(17)); +/// ``` +pub fn memrchr(needle: u8, haystack: &[u8]) -> Option<usize> { + + #[cfg(target_os = "linux")] + fn memrchr_specific(needle: u8, haystack: &[u8]) -> Option<usize> { + use libc; + + // GNU's memrchr() will - unlike memchr() - error if haystack is empty. + if haystack.is_empty() {return None} + let p = unsafe { + libc::memrchr( + haystack.as_ptr() as *const libc::c_void, + needle as libc::c_int, + haystack.len() as libc::size_t) + }; + if p.is_null() { + None + } else { + Some(p as usize - (haystack.as_ptr() as usize)) + } + } + + #[cfg(not(target_os = "linux"))] + fn memrchr_specific(needle: u8, haystack: &[u8]) -> Option<usize> { + haystack.iter().rposition(|&b| b == needle) + } + + memrchr_specific(needle, haystack) +} + +#[allow(dead_code)] +mod fallback { + use cmp; + use usize; + + 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 inital 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(); + + // 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(); + + // search to an aligned boundary + let end_align = (ptr as usize + len) & (usize::BYTES - 1); + let mut offset; + if end_align > 0 { + offset = len - cmp::min(usize::BYTES - end_align, len); + 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 plattforms + #[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")); + } +} + +#[cfg(test)] +mod tests { + // test the implementations for the current plattform + use super::{memchr, memrchr}; + + #[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")); + } +} diff --git a/src/libstd/sys/unix/os.rs b/src/libstd/sys/unix/os.rs index c2bf0651cff..12b9d6191a0 100644 --- a/src/libstd/sys/unix/os.rs +++ b/src/libstd/sys/unix/os.rs @@ -22,6 +22,7 @@ use io; use iter; use libc::{self, c_int, c_char, c_void}; use mem; +use memchr; use path::{self, PathBuf}; use ptr; use slice; @@ -406,7 +407,7 @@ pub fn env() -> Env { if input.is_empty() { return None; } - let pos = input[1..].iter().position(|&b| b == b'=').map(|p| p + 1); + let pos = memchr::memchr(b'=', &input[1..]).map(|p| p + 1); pos.map(|p| ( OsStringExt::from_vec(input[..p].to_vec()), OsStringExt::from_vec(input[p+1..].to_vec()), |