mirror of
https://github.com/jart/cosmopolitan.git
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62 lines
3.6 KiB
C
62 lines
3.6 KiB
C
/*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
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│ vi: set et ft=c ts=2 sts=2 sw=2 fenc=utf-8 :vi │
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╞══════════════════════════════════════════════════════════════════════════════╡
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│ Copyright 2020 Justine Alexandra Roberts Tunney │
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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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▄ ▄▄▄
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▄▄▓▓██▀░ ▄ ▄▓▌▀▀▀███▒
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▄ ░██░ ░▀▀ ▓▓█▓█▌ ▄▄▄██▀░ ▄▄░
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░▄▓██░ ░██▄ ▄▄▓▌ ▄▓███░ ░▄█▀▄▓▒
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░░▓█▓▄ ░▀██▒ ░▀█▄ ░▓██▓▄▒▄▄▀▀ ▄█▓▀▐██░
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▄███ ▀██▄ ▀▓█▓▄▄▓▀ ▀▀▀▀ ░▄▄█▀░▒▓██▓ ░░▄▄▄▄▄▄
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▄▄▓▀▐██ ░ ▓██▓▒ ▀▀ ▀▀▀ ▄▄██░ ▄▓██▓▀░░▀█░
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▀▒▓░ ▐██▓ ▓▓▒ ▀▀░ ▀▀▀█▒ ▓█▓▀░ ▄█▓▓░
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▒▀ ▒██▒░▄█▓▀ VARIABLE LENGTH INTEGER DECODING ▓█░ ▐▓▄ ░ ▓
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░███▓▀ ▀▓▓██▀▀░
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░▀░ */
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#include "libc/fmt/leb128.h"
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#include "libc/macros.h"
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/**
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* Decodes array to signed integer w/ zig-zag encoding.
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*
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* @param p is array
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* @param n is byte length of array
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* @param o optionally receives decoded integer
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* @return bytes decoded or -1 on error
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* @see zleb64()
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*/
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int unzleb64(const char *p, size_t n, int64_t *o) {
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int c;
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size_t i;
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uint64_t u, t;
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i = 0;
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u = 0;
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do {
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if (i == n)
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return -1;
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c = p[i] & 255;
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t = c & 127;
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if (i < 10) {
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t <<= i * 7;
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u |= t;
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}
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++i;
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} while (c & 128);
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if (o)
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*o = (u >> 1) ^ -(u & 1);
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return i;
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}
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