yading@11: /*
yading@11:  * Compute the Adler-32 checksum of a data stream.
yading@11:  * This is a modified version based on adler32.c from the zlib library.
yading@11:  *
yading@11:  * Copyright (C) 1995 Mark Adler
yading@11:  *
yading@11:  * This software is provided 'as-is', without any express or implied
yading@11:  * warranty.  In no event will the authors be held liable for any damages
yading@11:  * arising from the use of this software.
yading@11:  *
yading@11:  * Permission is granted to anyone to use this software for any purpose,
yading@11:  * including commercial applications, and to alter it and redistribute it
yading@11:  * freely, subject to the following restrictions:
yading@11:  *
yading@11:  * 1. The origin of this software must not be misrepresented; you must not
yading@11:  *    claim that you wrote the original software. If you use this software
yading@11:  *    in a product, an acknowledgment in the product documentation would be
yading@11:  *    appreciated but is not required.
yading@11:  * 2. Altered source versions must be plainly marked as such, and must not be
yading@11:  *    misrepresented as being the original software.
yading@11:  * 3. This notice may not be removed or altered from any source distribution.
yading@11:  */
yading@11: 
yading@11: #include "config.h"
yading@11: #include "adler32.h"
yading@11: #include "common.h"
yading@11: #include "intreadwrite.h"
yading@11: 
yading@11: #define BASE 65521L /* largest prime smaller than 65536 */
yading@11: 
yading@11: #define DO1(buf)  { s1 += *buf++; s2 += s1; }
yading@11: #define DO4(buf)  DO1(buf); DO1(buf); DO1(buf); DO1(buf);
yading@11: #define DO16(buf) DO4(buf); DO4(buf); DO4(buf); DO4(buf);
yading@11: 
yading@11: unsigned long av_adler32_update(unsigned long adler, const uint8_t * buf,
yading@11:                                 unsigned int len)
yading@11: {
yading@11:     unsigned long s1 = adler & 0xffff;
yading@11:     unsigned long s2 = adler >> 16;
yading@11: 
yading@11:     while (len > 0) {
yading@11: #if HAVE_FAST_64BIT && HAVE_FAST_UNALIGNED && !CONFIG_SMALL
yading@11:         unsigned len2 = FFMIN((len-1) & ~7, 23*8);
yading@11:         if (len2) {
yading@11:             uint64_t a1= 0;
yading@11:             uint64_t a2= 0;
yading@11:             uint64_t b1= 0;
yading@11:             uint64_t b2= 0;
yading@11:             len -= len2;
yading@11:             s2 += s1*len2;
yading@11:             while (len2 >= 8) {
yading@11:                 uint64_t v = AV_RN64(buf);
yading@11:                 a2 += a1;
yading@11:                 b2 += b1;
yading@11:                 a1 +=  v    &0x00FF00FF00FF00FF;
yading@11:                 b1 += (v>>8)&0x00FF00FF00FF00FF;
yading@11:                 len2 -= 8;
yading@11:                 buf+=8;
yading@11:             }
yading@11: 
yading@11:             //We combine the 8 interleaved adler32 checksums without overflows
yading@11:             //Decreasing the number of iterations would allow below code to be
yading@11:             //simplified but would likely be slower due to the fewer iterations
yading@11:             //of the inner loop
yading@11:             s1 += ((a1+b1)*0x1000100010001)>>48;
yading@11:             s2 += ((((a2&0xFFFF0000FFFF)+(b2&0xFFFF0000FFFF)+((a2>>16)&0xFFFF0000FFFF)+((b2>>16)&0xFFFF0000FFFF))*0x800000008)>>32)
yading@11: #if HAVE_BIGENDIAN
yading@11:                  + 2*((b1*0x1000200030004)>>48)
yading@11:                  +   ((a1*0x1000100010001)>>48)
yading@11:                  + 2*((a1*0x0000100020003)>>48);
yading@11: #else
yading@11:                  + 2*((a1*0x4000300020001)>>48)
yading@11:                  +   ((b1*0x1000100010001)>>48)
yading@11:                  + 2*((b1*0x3000200010000)>>48);
yading@11: #endif
yading@11:         }
yading@11: #else
yading@11:         while (len > 4  && s2 < (1U << 31)) {
yading@11:             DO4(buf);
yading@11:             len -= 4;
yading@11:         }
yading@11: #endif
yading@11:         DO1(buf); len--;
yading@11:         s1 %= BASE;
yading@11:         s2 %= BASE;
yading@11:     }
yading@11:     return (s2 << 16) | s1;
yading@11: }
yading@11: 
yading@11: #ifdef TEST
yading@11: // LCOV_EXCL_START
yading@11: #include <string.h>
yading@11: #include "log.h"
yading@11: #include "timer.h"
yading@11: #define LEN 7001
yading@11: 
yading@11: static volatile int checksum;
yading@11: 
yading@11: int main(int argc, char **argv)
yading@11: {
yading@11:     int i;
yading@11:     char data[LEN];
yading@11: 
yading@11:     av_log_set_level(AV_LOG_DEBUG);
yading@11: 
yading@11:     for (i = 0; i < LEN; i++)
yading@11:         data[i] = ((i * i) >> 3) + 123 * i;
yading@11: 
yading@11:     if (argc > 1 && !strcmp(argv[1], "-t")) {
yading@11:         for (i = 0; i < 1000; i++) {
yading@11:             START_TIMER;
yading@11:             checksum = av_adler32_update(1, data, LEN);
yading@11:             STOP_TIMER("adler");
yading@11:         }
yading@11:     } else {
yading@11:         checksum = av_adler32_update(1, data, LEN);
yading@11:     }
yading@11: 
yading@11:     av_log(NULL, AV_LOG_DEBUG, "%X (expected 50E6E508)\n", checksum);
yading@11:     return checksum == 0x50e6e508 ? 0 : 1;
yading@11: }
yading@11: // LCOV_EXCL_STOP
yading@11: #endif