blob: c87d5e261c4803b86d888dc180d7c3c1d34d526c
| 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 "common.h" |
| 36 | #include "intreadwrite.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 | unsigned long av_adler32_update(unsigned long adler, const uint8_t * buf, |
| 45 | unsigned int len) |
| 46 | { |
| 47 | unsigned long s1 = adler & 0xffff; |
| 48 | unsigned long s2 = adler >> 16; |
| 49 | |
| 50 | while (len > 0) { |
| 51 | #if HAVE_FAST_64BIT && HAVE_FAST_UNALIGNED && !CONFIG_SMALL |
| 52 | unsigned len2 = FFMIN((len-1) & ~7, 23*8); |
| 53 | if (len2) { |
| 54 | uint64_t a1= 0; |
| 55 | uint64_t a2= 0; |
| 56 | uint64_t b1= 0; |
| 57 | uint64_t b2= 0; |
| 58 | len -= len2; |
| 59 | s2 += s1*len2; |
| 60 | while (len2 >= 8) { |
| 61 | uint64_t v = AV_RN64(buf); |
| 62 | a2 += a1; |
| 63 | b2 += b1; |
| 64 | a1 += v &0x00FF00FF00FF00FF; |
| 65 | b1 += (v>>8)&0x00FF00FF00FF00FF; |
| 66 | len2 -= 8; |
| 67 | buf+=8; |
| 68 | } |
| 69 | |
| 70 | //We combine the 8 interleaved adler32 checksums without overflows |
| 71 | //Decreasing the number of iterations would allow below code to be |
| 72 | //simplified but would likely be slower due to the fewer iterations |
| 73 | //of the inner loop |
| 74 | s1 += ((a1+b1)*0x1000100010001)>>48; |
| 75 | s2 += ((((a2&0xFFFF0000FFFF)+(b2&0xFFFF0000FFFF)+((a2>>16)&0xFFFF0000FFFF)+((b2>>16)&0xFFFF0000FFFF))*0x800000008)>>32) |
| 76 | #if HAVE_BIGENDIAN |
| 77 | + 2*((b1*0x1000200030004)>>48) |
| 78 | + ((a1*0x1000100010001)>>48) |
| 79 | + 2*((a1*0x0000100020003)>>48); |
| 80 | #else |
| 81 | + 2*((a1*0x4000300020001)>>48) |
| 82 | + ((b1*0x1000100010001)>>48) |
| 83 | + 2*((b1*0x3000200010000)>>48); |
| 84 | #endif |
| 85 | } |
| 86 | #else |
| 87 | while (len > 4 && s2 < (1U << 31)) { |
| 88 | DO4(buf); |
| 89 | len -= 4; |
| 90 | } |
| 91 | #endif |
| 92 | DO1(buf); len--; |
| 93 | s1 %= BASE; |
| 94 | s2 %= BASE; |
| 95 | } |
| 96 | return (s2 << 16) | s1; |
| 97 | } |
| 98 |