adler32.c (3290B)
1 /* 2 * Compute the Adler-32 checksum of a data stream. 3 * This is a modified version based on adler32.c from the zlib library. 4 * 5 * Copyright (C) 1995 Mark Adler 6 * 7 * This software is provided 'as-is', without any express or implied 8 * warranty. In no event will the authors be held liable for any damages 9 * arising from the use of this software. 10 * 11 * Permission is granted to anyone to use this software for any purpose, 12 * including commercial applications, and to alter it and redistribute it 13 * freely, subject to the following restrictions: 14 * 15 * 1. The origin of this software must not be misrepresented; you must not 16 * claim that you wrote the original software. If you use this software 17 * in a product, an acknowledgment in the product documentation would be 18 * appreciated but is not required. 19 * 2. Altered source versions must be plainly marked as such, and must not be 20 * misrepresented as being the original software. 21 * 3. This notice may not be removed or altered from any source distribution. 22 */ 23 24 /** 25 * @file 26 * Computes the Adler-32 checksum of a data stream 27 * 28 * This is a modified version based on adler32.c from the zlib library. 29 * @author Mark Adler 30 * @ingroup lavu_adler32 31 */ 32 33 #include "config.h" 34 #include "adler32.h" 35 #include "intreadwrite.h" 36 #include "macros.h" 37 38 #define BASE 65521L /* largest prime smaller than 65536 */ 39 40 #define DO1(buf) { s1 += *buf++; s2 += s1; } 41 #define DO4(buf) DO1(buf); DO1(buf); DO1(buf); DO1(buf); 42 #define DO16(buf) DO4(buf); DO4(buf); DO4(buf); DO4(buf); 43 44 AVAdler av_adler32_update(AVAdler adler, const uint8_t *buf, size_t len) 45 { 46 unsigned long s1 = adler & 0xffff; 47 unsigned long s2 = adler >> 16; 48 49 while (len > 0) { 50 #if HAVE_FAST_64BIT && HAVE_FAST_UNALIGNED && !CONFIG_SMALL 51 unsigned len2 = FFMIN((len-1) & ~7, 23*8); 52 if (len2) { 53 uint64_t a1= 0; 54 uint64_t a2= 0; 55 uint64_t b1= 0; 56 uint64_t b2= 0; 57 len -= len2; 58 s2 += s1*len2; 59 while (len2 >= 8) { 60 uint64_t v = AV_RN64(buf); 61 a2 += a1; 62 b2 += b1; 63 a1 += v &0x00FF00FF00FF00FF; 64 b1 += (v>>8)&0x00FF00FF00FF00FF; 65 len2 -= 8; 66 buf+=8; 67 } 68 69 //We combine the 8 interleaved adler32 checksums without overflows 70 //Decreasing the number of iterations would allow below code to be 71 //simplified but would likely be slower due to the fewer iterations 72 //of the inner loop 73 s1 += ((a1+b1)*0x1000100010001)>>48; 74 s2 += ((((a2&0xFFFF0000FFFF)+(b2&0xFFFF0000FFFF)+((a2>>16)&0xFFFF0000FFFF)+((b2>>16)&0xFFFF0000FFFF))*0x800000008)>>32) 75 #if HAVE_BIGENDIAN 76 + 2*((b1*0x1000200030004)>>48) 77 + ((a1*0x1000100010001)>>48) 78 + 2*((a1*0x0000100020003)>>48); 79 #else 80 + 2*((a1*0x4000300020001)>>48) 81 + ((b1*0x1000100010001)>>48) 82 + 2*((b1*0x3000200010000)>>48); 83 #endif 84 } 85 #else 86 while (len > 4 && s2 < (1U << 31)) { 87 DO4(buf); 88 len -= 4; 89 } 90 #endif 91 DO1(buf); len--; 92 s1 %= BASE; 93 s2 %= BASE; 94 } 95 return (s2 << 16) | s1; 96 }