| /* |
| * 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. |
| */ |
| |
| /** |
| * @file |
| * Computes the Adler-32 checksum of a data stream |
| * |
| * This is a modified version based on adler32.c from the zlib library. |
| * @author Mark Adler |
| * @ingroup lavu_adler32 |
| */ |
| |
| #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; |
| } |