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133 lines
4.1 KiB
C
133 lines
4.1 KiB
C
/* adler32.c -- compute the Adler-32 checksum of a data stream
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* Copyright (C) 1995-2011, 2016 Mark Adler
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* For conditions of distribution and use, see copyright notice in zlib.h
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*/
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/* @(#) $Id$ */
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#include "zbuild.h"
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#include "zutil.h"
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#include "functable.h"
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#include "adler32_p.h"
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uint32_t adler32_c(uint32_t adler, const unsigned char *buf, size_t len);
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static uint32_t adler32_combine_(uint32_t adler1, uint32_t adler2, z_off64_t len2);
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#define DO1(buf, i) {adler += (buf)[i]; sum2 += adler;}
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#define DO2(buf, i) DO1(buf, i); DO1(buf, i+1);
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#define DO4(buf, i) DO2(buf, i); DO2(buf, i+2);
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#define DO8(buf, i) DO4(buf, i); DO4(buf, i+4);
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#define DO16(buf) DO8(buf, 0); DO8(buf, 8);
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/* ========================================================================= */
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uint32_t adler32_c(uint32_t adler, const unsigned char *buf, size_t len) {
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uint32_t sum2;
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unsigned n;
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/* split Adler-32 into component sums */
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sum2 = (adler >> 16) & 0xffff;
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adler &= 0xffff;
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/* in case user likes doing a byte at a time, keep it fast */
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if (len == 1)
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return adler32_len_1(adler, buf, sum2);
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/* initial Adler-32 value (deferred check for len == 1 speed) */
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if (buf == NULL)
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return 1L;
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/* in case short lengths are provided, keep it somewhat fast */
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if (len < 16)
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return adler32_len_16(adler, buf, len, sum2);
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/* do length NMAX blocks -- requires just one modulo operation */
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while (len >= NMAX) {
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len -= NMAX;
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#ifdef UNROLL_MORE
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n = NMAX / 16; /* NMAX is divisible by 16 */
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#else
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n = NMAX / 8; /* NMAX is divisible by 8 */
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#endif
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do {
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#ifdef UNROLL_MORE
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DO16(buf); /* 16 sums unrolled */
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buf += 16;
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#else
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DO8(buf, 0); /* 8 sums unrolled */
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buf += 8;
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#endif
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} while (--n);
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MOD(adler);
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MOD(sum2);
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}
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/* do remaining bytes (less than NMAX, still just one modulo) */
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if (len) { /* avoid modulos if none remaining */
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#ifdef UNROLL_MORE
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while (len >= 16) {
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len -= 16;
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DO16(buf);
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buf += 16;
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#else
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while (len >= 8) {
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len -= 8;
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DO8(buf, 0);
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buf += 8;
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#endif
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}
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while (len) {
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--len;
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adler += *buf++;
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sum2 += adler;
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}
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MOD(adler);
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MOD(sum2);
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}
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/* return recombined sums */
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return adler | (sum2 << 16);
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}
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uint32_t ZEXPORT PREFIX(adler32_z)(uint32_t adler, const unsigned char *buf, size_t len) {
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return functable.adler32(adler, buf, len);
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}
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/* ========================================================================= */
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uint32_t ZEXPORT PREFIX(adler32)(uint32_t adler, const unsigned char *buf, uint32_t len) {
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return functable.adler32(adler, buf, len);
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}
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/* ========================================================================= */
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static uint32_t adler32_combine_(uint32_t adler1, uint32_t adler2, z_off64_t len2) {
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uint32_t sum1;
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uint32_t sum2;
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unsigned rem;
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/* for negative len, return invalid adler32 as a clue for debugging */
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if (len2 < 0)
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return 0xffffffff;
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/* the derivation of this formula is left as an exercise for the reader */
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MOD63(len2); /* assumes len2 >= 0 */
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rem = (unsigned)len2;
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sum1 = adler1 & 0xffff;
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sum2 = rem * sum1;
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MOD(sum2);
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sum1 += (adler2 & 0xffff) + BASE - 1;
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sum2 += ((adler1 >> 16) & 0xffff) + ((adler2 >> 16) & 0xffff) + BASE - rem;
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if (sum1 >= BASE) sum1 -= BASE;
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if (sum1 >= BASE) sum1 -= BASE;
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if (sum2 >= ((unsigned long)BASE << 1)) sum2 -= ((unsigned long)BASE << 1);
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if (sum2 >= BASE) sum2 -= BASE;
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return sum1 | (sum2 << 16);
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}
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/* ========================================================================= */
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uint32_t ZEXPORT PREFIX(adler32_combine)(uint32_t adler1, uint32_t adler2, z_off_t len2) {
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return adler32_combine_(adler1, adler2, len2);
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}
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uint32_t ZEXPORT PREFIX(adler32_combine64)(uint32_t adler1, uint32_t adler2, z_off64_t len2) {
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return adler32_combine_(adler1, adler2, len2);
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}
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