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115 lines
3.9 KiB
115 lines
3.9 KiB
/* 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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#include "zbuild.h" |
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#include "functable.h" |
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#include "adler32_p.h" |
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/* ========================================================================= */ |
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Z_INTERNAL uint32_t adler32_c(uint32_t adler, const uint8_t *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 (UNLIKELY(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 (UNLIKELY(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 (UNLIKELY(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(adler, sum2, buf); /* 16 sums unrolled */ |
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buf += 16; |
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#else |
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DO8(adler, sum2, 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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adler %= BASE; |
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sum2 %= BASE; |
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} |
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/* do remaining bytes (less than NMAX, still just one modulo) */ |
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return adler32_len_64(adler, buf, len, sum2); |
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} |
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#ifdef ZLIB_COMPAT |
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unsigned long Z_EXPORT PREFIX(adler32_z)(unsigned long adler, const unsigned char *buf, size_t len) { |
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return (unsigned long)functable.adler32((uint32_t)adler, buf, len); |
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} |
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#else |
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uint32_t Z_EXPORT 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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#endif |
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/* ========================================================================= */ |
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#ifdef ZLIB_COMPAT |
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unsigned long Z_EXPORT PREFIX(adler32)(unsigned long adler, const unsigned char *buf, unsigned int len) { |
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return (unsigned long)functable.adler32((uint32_t)adler, buf, len); |
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} |
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#else |
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uint32_t Z_EXPORT 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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#endif |
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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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len2 %= BASE; /* 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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sum2 %= BASE; |
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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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#ifdef ZLIB_COMPAT |
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unsigned long Z_EXPORT PREFIX(adler32_combine)(unsigned long adler1, unsigned long adler2, z_off_t len2) { |
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return (unsigned long)adler32_combine_((uint32_t)adler1, (uint32_t)adler2, len2); |
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} |
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unsigned long Z_EXPORT PREFIX4(adler32_combine)(unsigned long adler1, unsigned long adler2, z_off64_t len2) { |
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return (unsigned long)adler32_combine_((uint32_t)adler1, (uint32_t)adler2, len2); |
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} |
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#else |
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uint32_t Z_EXPORT PREFIX4(adler32_combine)(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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#endif
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