+++ /dev/null
-/* adler32.c -- compute the Adler-32 checksum of a data stream\r
- * Copyright (C) 1995-2004 Mark Adler\r
- * For conditions of distribution and use, see copyright notice in zlib.h\r
- */\r
-\r
-/* @(#) $Id$ */\r
-\r
-#define ZLIB_INTERNAL\r
-#include "zlib.h"\r
-\r
-#define BASE 65521UL /* largest prime smaller than 65536 */\r
-#define NMAX 5552\r
-/* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */\r
-\r
-#define DO1(buf,i) {adler += (buf)[i]; sum2 += adler;}\r
-#define DO2(buf,i) DO1(buf,i); DO1(buf,i+1);\r
-#define DO4(buf,i) DO2(buf,i); DO2(buf,i+2);\r
-#define DO8(buf,i) DO4(buf,i); DO4(buf,i+4);\r
-#define DO16(buf) DO8(buf,0); DO8(buf,8);\r
-\r
-/* use NO_DIVIDE if your processor does not do division in hardware */\r
-#ifdef NO_DIVIDE\r
-# define MOD(a) \\r
- do { \\r
- if (a >= (BASE << 16)) a -= (BASE << 16); \\r
- if (a >= (BASE << 15)) a -= (BASE << 15); \\r
- if (a >= (BASE << 14)) a -= (BASE << 14); \\r
- if (a >= (BASE << 13)) a -= (BASE << 13); \\r
- if (a >= (BASE << 12)) a -= (BASE << 12); \\r
- if (a >= (BASE << 11)) a -= (BASE << 11); \\r
- if (a >= (BASE << 10)) a -= (BASE << 10); \\r
- if (a >= (BASE << 9)) a -= (BASE << 9); \\r
- if (a >= (BASE << 8)) a -= (BASE << 8); \\r
- if (a >= (BASE << 7)) a -= (BASE << 7); \\r
- if (a >= (BASE << 6)) a -= (BASE << 6); \\r
- if (a >= (BASE << 5)) a -= (BASE << 5); \\r
- if (a >= (BASE << 4)) a -= (BASE << 4); \\r
- if (a >= (BASE << 3)) a -= (BASE << 3); \\r
- if (a >= (BASE << 2)) a -= (BASE << 2); \\r
- if (a >= (BASE << 1)) a -= (BASE << 1); \\r
- if (a >= BASE) a -= BASE; \\r
- } while (0)\r
-# define MOD4(a) \\r
- do { \\r
- if (a >= (BASE << 4)) a -= (BASE << 4); \\r
- if (a >= (BASE << 3)) a -= (BASE << 3); \\r
- if (a >= (BASE << 2)) a -= (BASE << 2); \\r
- if (a >= (BASE << 1)) a -= (BASE << 1); \\r
- if (a >= BASE) a -= BASE; \\r
- } while (0)\r
-#else\r
-# define MOD(a) a %= BASE\r
-# define MOD4(a) a %= BASE\r
-#endif\r
-\r
-/* ========================================================================= */\r
-uLong ZEXPORT adler32(adler, buf, len)\r
- uLong adler;\r
- const Bytef *buf;\r
- uInt len;\r
-{\r
- unsigned long sum2;\r
- unsigned n;\r
-\r
- /* split Adler-32 into component sums */\r
- sum2 = (adler >> 16) & 0xffff;\r
- adler &= 0xffff;\r
-\r
- /* in case user likes doing a byte at a time, keep it fast */\r
- if (len == 1) {\r
- adler += buf[0];\r
- if (adler >= BASE)\r
- adler -= BASE;\r
- sum2 += adler;\r
- if (sum2 >= BASE)\r
- sum2 -= BASE;\r
- return adler | (sum2 << 16);\r
- }\r
-\r
- /* initial Adler-32 value (deferred check for len == 1 speed) */\r
- if (buf == Z_NULL)\r
- return 1L;\r
-\r
- /* in case short lengths are provided, keep it somewhat fast */\r
- if (len < 16) {\r
- while (len--) {\r
- adler += *buf++;\r
- sum2 += adler;\r
- }\r
- if (adler >= BASE)\r
- adler -= BASE;\r
- MOD4(sum2); /* only added so many BASE's */\r
- return adler | (sum2 << 16);\r
- }\r
-\r
- /* do length NMAX blocks -- requires just one modulo operation */\r
- while (len >= NMAX) {\r
- len -= NMAX;\r
- n = NMAX / 16; /* NMAX is divisible by 16 */\r
- do {\r
- DO16(buf); /* 16 sums unrolled */\r
- buf += 16;\r
- } while (--n);\r
- MOD(adler);\r
- MOD(sum2);\r
- }\r
-\r
- /* do remaining bytes (less than NMAX, still just one modulo) */\r
- if (len) { /* avoid modulos if none remaining */\r
- while (len >= 16) {\r
- len -= 16;\r
- DO16(buf);\r
- buf += 16;\r
- }\r
- while (len--) {\r
- adler += *buf++;\r
- sum2 += adler;\r
- }\r
- MOD(adler);\r
- MOD(sum2);\r
- }\r
-\r
- /* return recombined sums */\r
- return adler | (sum2 << 16);\r
-}\r
-\r
-/* ========================================================================= */\r
-uLong ZEXPORT adler32_combine(adler1, adler2, len2)\r
- uLong adler1;\r
- uLong adler2;\r
- z_off_t len2;\r
-{\r
- unsigned long sum1;\r
- unsigned long sum2;\r
- unsigned rem;\r
-\r
- /* the derivation of this formula is left as an exercise for the reader */\r
- rem = (unsigned)(len2 % BASE);\r
- sum1 = adler1 & 0xffff;\r
- sum2 = rem * sum1;\r
- MOD(sum2);\r
- sum1 += (adler2 & 0xffff) + BASE - 1;\r
- sum2 += ((adler1 >> 16) & 0xffff) + ((adler2 >> 16) & 0xffff) + BASE - rem;\r
- if (sum1 > BASE) sum1 -= BASE;\r
- if (sum1 > BASE) sum1 -= BASE;\r
- if (sum2 > (BASE << 1)) sum2 -= (BASE << 1);\r
- if (sum2 > BASE) sum2 -= BASE;\r
- return sum1 | (sum2 << 16);\r
-}\r