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https://github.com/jart/cosmopolitan.git
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39bf41f4eb
- Python static hello world now 1.8mb
- Python static fully loaded now 10mb
- Python HTTPS client now uses MbedTLS
- Python REPL now completes import stmts
- Increase stack size for Python for now
- Begin synthesizing posixpath and ntpath
- Restore Python \N{UNICODE NAME} support
- Restore Python NFKD symbol normalization
- Add optimized code path for Intel SHA-NI
- Get more Python unit tests passing faster
- Get Python help() pagination working on NT
- Python hashlib now supports MbedTLS PBKDF2
- Make memcpy/memmove/memcmp/bcmp/etc. faster
- Add Mersenne Twister and Vigna to LIBC_RAND
- Provide privileged __printf() for error code
- Fix zipos opendir() so that it reports ENOTDIR
- Add basic chmod() implementation for Windows NT
- Add Cosmo's best functions to Python cosmo module
- Pin function trace indent depth to that of caller
- Show memory diagram on invalid access in MODE=dbg
- Differentiate stack overflow on crash in MODE=dbg
- Add stb_truetype and tools for analyzing font files
- Upgrade to UNICODE 13 and reduce its binary footprint
- COMPILE.COM now logs resource usage of build commands
- Start implementing basic poll() support on bare metal
- Set getauxval(AT_EXECFN) to GetModuleFileName() on NT
- Add descriptions to strerror() in non-TINY build modes
- Add COUNTBRANCH() macro to help with micro-optimizations
- Make error / backtrace / asan / memory code more unbreakable
- Add fast perfect C implementation of μ-Law and a-Law audio codecs
- Make strtol() functions consistent with other libc implementations
- Improve Linenoise implementation (see also github.com/jart/bestline)
- COMPILE.COM now suppresses stdout/stderr of successful build commands
95 lines
5.3 KiB
C
95 lines
5.3 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi│
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2014 Google Inc. │
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│ │
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│ Permission to use, copy, modify, and/or distribute this software for │
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│ any purpose with or without fee is hereby granted, provided that the │
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│ above copyright notice and this permission notice appear in all copies. │
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│ │
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│ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL │
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│ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED │
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│ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE │
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│ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL │
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│ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR │
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│ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER │
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│ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR │
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│ PERFORMANCE OF THIS SOFTWARE. │
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╚─────────────────────────────────────────────────────────────────────────────*/
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#include "libc/str/str.h"
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asm(".ident\t\"\\n\\n\
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timingsafe_memcmp (ISC License)\\n\
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Copyright 2014 Google Inc.\"");
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asm(".include \"libc/disclaimer.inc\"");
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/**
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* Lexicographically compares the first 𝑛 bytes in 𝑝 and 𝑞.
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*
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* The following expression:
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*
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* timingsafe_memcmp(p, q, n)
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*
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* Is functionally equivalent to:
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*
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* MAX(-1, MIN(1, memcmp(p, q, n)))
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*
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* Running time is independent of the byte sequences compared, making
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* this safe to use for comparing secret values such as cryptographic
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* MACs. In contrast, memcmp() may short-circuit after finding the first
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* differing byte.
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*
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* timingsafe_memcmp n=0 661 picoseconds
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* timingsafe_memcmp n=1 1 ns/byte 590 mb/s
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* timingsafe_memcmp n=2 1 ns/byte 738 mb/s
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* timingsafe_memcmp n=3 1 ns/byte 805 mb/s
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* timingsafe_memcmp n=4 1 ns/byte 843 mb/s
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* timingsafe_memcmp n=5 1 ns/byte 922 mb/s
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* timingsafe_memcmp n=6 1 ns/byte 932 mb/s
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* timingsafe_memcmp n=7 1 ns/byte 939 mb/s
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* timingsafe_memcmp n=8 992 ps/byte 984 mb/s
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* timingsafe_memcmp n=9 992 ps/byte 984 mb/s
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* timingsafe_memcmp n=15 926 ps/byte 1,054 mb/s
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* timingsafe_memcmp n=16 950 ps/byte 1,026 mb/s
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* timingsafe_memcmp n=17 933 ps/byte 1,045 mb/s
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* timingsafe_memcmp n=31 896 ps/byte 1,089 mb/s
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* timingsafe_memcmp n=32 888 ps/byte 1,098 mb/s
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* timingsafe_memcmp n=33 972 ps/byte 1,004 mb/s
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* timingsafe_memcmp n=80 913 ps/byte 1,068 mb/s
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* timingsafe_memcmp n=128 891 ps/byte 1,095 mb/s
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* timingsafe_memcmp n=256 873 ps/byte 1,118 mb/s
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* timingsafe_memcmp n=16384 858 ps/byte 1,138 mb/s
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* timingsafe_memcmp n=32768 856 ps/byte 1,140 mb/s
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* timingsafe_memcmp n=131072 857 ps/byte 1,138 mb/s
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* bcmp ne n=256 3 ps/byte 246 gb/s
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* bcmp eq n=256 32 ps/byte 30,233 mb/s
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* memcmp ne n=256 3 ps/byte 246 gb/s
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* memcmp eq n=256 31 ps/byte 31,493 mb/s
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* timingsafe_bcmp ne n=256 27 ps/byte 35,992 mb/s
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* timingsafe_bcmp eq n=256 27 ps/byte 35,992 mb/s
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* timingsafe_memcmp ne n=256 877 ps/byte 1,113 mb/s
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* timingsafe_memcmp eq n=256 883 ps/byte 1,105 mb/s
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*
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* @note each byte is interpreted as unsigned char
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* @return -1, 0, or 1 based on comparison
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* @see timingsafe_bcmp() it's 100x faster
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* @asyncsignalsafe
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*/
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int timingsafe_memcmp(const void *p, const void *q, size_t n) {
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const unsigned char *p1 = p, *p2 = q;
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size_t i;
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int res = 0, done = 0;
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for (i = 0; i < n; i++) {
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/* lt is -1 if p1[i] < p2[i]; else 0. */
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int lt = (p1[i] - p2[i]) >> CHAR_BIT;
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/* gt is -1 if p1[i] > p2[i]; else 0. */
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int gt = (p2[i] - p1[i]) >> CHAR_BIT;
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/* cmp is 1 if p1[i] > p2[i]; -1 if p1[i] < p2[i]; else 0. */
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int cmp = lt - gt;
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/* set res = cmp if !done. */
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res |= cmp & ~done;
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/* set done if p1[i] != p2[i]. */
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done |= lt | gt;
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}
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return res;
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}
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