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Diffstat (limited to 'ctr-std/src/sys_common/memchr.rs')
| -rw-r--r-- | ctr-std/src/sys_common/memchr.rs | 230 |
1 files changed, 0 insertions, 230 deletions
diff --git a/ctr-std/src/sys_common/memchr.rs b/ctr-std/src/sys_common/memchr.rs deleted file mode 100644 index 3824a5f..0000000 --- a/ctr-std/src/sys_common/memchr.rs +++ /dev/null @@ -1,230 +0,0 @@ -// 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..])); - } - } -} |