/* * Compute the Adler-32 checksum of a data stream. * This is a modified version based on adler32.c from the zlib library. * * Copyright (C) 1995 Mark Adler * * This software is provided 'as-is', without any express or implied * warranty. In no event will the authors be held liable for any damages * arising from the use of this software. * * Permission is granted to anyone to use this software for any purpose, * including commercial applications, and to alter it and redistribute it * freely, subject to the following restrictions: * * 1. The origin of this software must not be misrepresented; you must not * claim that you wrote the original software. If you use this software * in a product, an acknowledgment in the product documentation would be * appreciated but is not required. * 2. Altered source versions must be plainly marked as such, and must not be * misrepresented as being the original software. * 3. This notice may not be removed or altered from any source distribution. */ #include "config.h" #include "adler32.h" #include "common.h" #include "intreadwrite.h" #define BASE 65521L /* largest prime smaller than 65536 */ #define DO1(buf) { s1 += *buf++; s2 += s1; } #define DO4(buf) DO1(buf); DO1(buf); DO1(buf); DO1(buf); #define DO16(buf) DO4(buf); DO4(buf); DO4(buf); DO4(buf); unsigned long av_adler32_update(unsigned long adler, const uint8_t * buf, unsigned int len) { unsigned long s1 = adler & 0xffff; unsigned long s2 = adler >> 16; while (len > 0) { #if HAVE_FAST_64BIT && HAVE_FAST_UNALIGNED && !CONFIG_SMALL unsigned len2 = FFMIN((len-1) & ~7, 23*8); if (len2) { uint64_t a1= 0; uint64_t a2= 0; uint64_t b1= 0; uint64_t b2= 0; len -= len2; s2 += s1*len2; while (len2 >= 8) { uint64_t v = AV_RN64(buf); a2 += a1; b2 += b1; a1 += v &0x00FF00FF00FF00FF; b1 += (v>>8)&0x00FF00FF00FF00FF; len2 -= 8; buf+=8; } //We combine the 8 interleaved adler32 checksums without overflows //Decreasing the number of iterations would allow below code to be //simplified but would likely be slower due to the fewer iterations //of the inner loop s1 += ((a1+b1)*0x1000100010001)>>48; s2 += ((((a2&0xFFFF0000FFFF)+(b2&0xFFFF0000FFFF)+((a2>>16)&0xFFFF0000FFFF)+((b2>>16)&0xFFFF0000FFFF))*0x800000008)>>32) #if HAVE_BIGENDIAN + 2*((b1*0x1000200030004)>>48) + ((a1*0x1000100010001)>>48) + 2*((a1*0x0000100020003)>>48); #else + 2*((a1*0x4000300020001)>>48) + ((b1*0x1000100010001)>>48) + 2*((b1*0x3000200010000)>>48); #endif } #else while (len > 4 && s2 < (1U << 31)) { DO4(buf); len -= 4; } #endif DO1(buf); len--; s1 %= BASE; s2 %= BASE; } return (s2 << 16) | s1; } #ifdef TEST // LCOV_EXCL_START #include <string.h> #include "log.h" #include "timer.h" #define LEN 7001 static volatile int checksum; int main(int argc, char **argv) { int i; char data[LEN]; av_log_set_level(AV_LOG_DEBUG); for (i = 0; i < LEN; i++) data[i] = ((i * i) >> 3) + 123 * i; if (argc > 1 && !strcmp(argv[1], "-t")) { for (i = 0; i < 1000; i++) { START_TIMER; checksum = av_adler32_update(1, data, LEN); STOP_TIMER("adler"); } } else { checksum = av_adler32_update(1, data, LEN); } av_log(NULL, AV_LOG_DEBUG, "%X (expected 50E6E508)\n", checksum); return checksum == 0x50e6e508 ? 0 : 1; } // LCOV_EXCL_STOP #endif