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/* adler32.c -- compute the Adler-32 checksum of a data stream
* Copyright (C) 1995-2011, 2016 Mark Adler
* For conditions of distribution and use, see copyright notice in zlib.h
*/
#include "zbuild.h"
#include "functable.h"
#include "adler32_p.h"
/* ========================================================================= */
Z_INTERNAL uint32_t adler32_c(uint32_t adler, const uint8_t *buf, size_t len) {
uint32_t sum2;
unsigned n;
/* split Adler-32 into component sums */
sum2 = (adler >> 16) & 0xffff;
adler &= 0xffff;
/* in case user likes doing a byte at a time, keep it fast */
if (UNLIKELY(len == 1))
return adler32_len_1(adler, buf, sum2);
/* initial Adler-32 value (deferred check for len == 1 speed) */
if (UNLIKELY(buf == NULL))
return 1L;
/* in case short lengths are provided, keep it somewhat fast */
if (UNLIKELY(len < 16))
return adler32_len_16(adler, buf, len, sum2);
/* do length NMAX blocks -- requires just one modulo operation */
while (len >= NMAX) {
len -= NMAX;
#ifdef UNROLL_MORE
n = NMAX / 16; /* NMAX is divisible by 16 */
#else
n = NMAX / 8; /* NMAX is divisible by 8 */
#endif
do {
#ifdef UNROLL_MORE
DO16(adler, sum2, buf); /* 16 sums unrolled */
buf += 16;
#else
DO8(adler, sum2, buf, 0); /* 8 sums unrolled */
buf += 8;
#endif
} while (--n);
adler %= BASE;
sum2 %= BASE;
}
/* do remaining bytes (less than NMAX, still just one modulo) */
return adler32_len_64(adler, buf, len, sum2);
}
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