1311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff/* adler32.c -- compute the Adler-32 checksum of a data stream 2311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff * Copyright (C) 1995-2004 Mark Adler 3311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff * For conditions of distribution and use, see copyright notice in zlib.h 4311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff */ 5311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 6311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff/* @(#) $Id$ */ 7311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 8311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff#define ZLIB_INTERNAL 9311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff#include "zlib.h" 10311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 11311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff#define BASE 65521UL /* largest prime smaller than 65536 */ 12311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff#define NMAX 5552 13311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff/* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */ 14311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 15311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff#define DO1(buf,i) {adler += (buf)[i]; sum2 += adler;} 16311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff#define DO2(buf,i) DO1(buf,i); DO1(buf,i+1); 17311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff#define DO4(buf,i) DO2(buf,i); DO2(buf,i+2); 18311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff#define DO8(buf,i) DO4(buf,i); DO4(buf,i+4); 19311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff#define DO16(buf) DO8(buf,0); DO8(buf,8); 20311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 21311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff/* use NO_DIVIDE if your processor does not do division in hardware */ 22311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff#ifdef NO_DIVIDE 23311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff# define MOD(a) \ 24311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff do { \ 25311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= (BASE << 16)) a -= (BASE << 16); \ 26311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= (BASE << 15)) a -= (BASE << 15); \ 27311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= (BASE << 14)) a -= (BASE << 14); \ 28311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= (BASE << 13)) a -= (BASE << 13); \ 29311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= (BASE << 12)) a -= (BASE << 12); \ 30311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= (BASE << 11)) a -= (BASE << 11); \ 31311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= (BASE << 10)) a -= (BASE << 10); \ 32311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= (BASE << 9)) a -= (BASE << 9); \ 33311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= (BASE << 8)) a -= (BASE << 8); \ 34311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= (BASE << 7)) a -= (BASE << 7); \ 35311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= (BASE << 6)) a -= (BASE << 6); \ 36311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= (BASE << 5)) a -= (BASE << 5); \ 37311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= (BASE << 4)) a -= (BASE << 4); \ 38311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= (BASE << 3)) a -= (BASE << 3); \ 39311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= (BASE << 2)) a -= (BASE << 2); \ 40311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= (BASE << 1)) a -= (BASE << 1); \ 41311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= BASE) a -= BASE; \ 42311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff } while (0) 43311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff# define MOD4(a) \ 44311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff do { \ 45311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= (BASE << 4)) a -= (BASE << 4); \ 46311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= (BASE << 3)) a -= (BASE << 3); \ 47311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= (BASE << 2)) a -= (BASE << 2); \ 48311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= (BASE << 1)) a -= (BASE << 1); \ 49311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (a >= BASE) a -= BASE; \ 50311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff } while (0) 51311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff#else 52311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff# define MOD(a) a %= BASE 53311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff# define MOD4(a) a %= BASE 54311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff#endif 55311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 56311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff/* ========================================================================= */ 57311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 58311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff/* 59311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff The adler32 code below computes, in effect, 60311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 61311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff uLong high = 0; 62311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff uLong low = 1; 63311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff for (j = 0; j < len; j++) { 64311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff low = (low + buf[j]) % BASE; 65311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff high = (high + low) % BASE; 66311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff } 67311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff checksum = (high << 16) | low; 68311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 69311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff Both 16-bit halves of the checksum are between 0 and BASE-1 (inclusive). 70311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff Hence, the minimum possible checksum value is 0, and the maximum is 71311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff ((BASE-1) << 16) | (BASE-1). Applications may have reserved values 72311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff outside this range to carry special meanings. 73311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 74311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff NOTE: If adler32() is changed in ANY way, be absolutely sure that the 75311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff change will NOT cause checksums previously stored to not match the data 76311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff they were originally intended to match, or expand the range in such a 77311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff way that values reserved by applications to carry special meanings now 78311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff become checksums of valid data. Also, be sure to change adler32_range() 79311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff accordingly. 80311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 81311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff This explanation and adler32_range() are not part of original software 82311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff distribution. They are added at Google (2006) in accordance with the 83311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff copyright notice in zlib.h, which permits alteration and redistribution 84311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff of the original software provided, among other things, that altered 85311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff source versions must be plainly marked as such and not misrepresented as 86311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff being the original software. 87311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff*/ 88311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 89311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiffvoid ZEXPORT adler32_range(min, max) 90311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff uLong *min; 91311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff uLong *max; 92311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff{ 93311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff *min = 0L; 94311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff *max = ((BASE-1) << 16) | (BASE-1); 95311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff} 96311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 97311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiffuLong ZEXPORT adler32(adler, buf, len) 98311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff uLong adler; 99311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff const Bytef *buf; 100311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff uInt len; 101311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff{ 102311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff unsigned long sum2; 103311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff unsigned n; 104311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 105311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff /* split Adler-32 into component sums */ 106311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff sum2 = (adler >> 16) & 0xffff; 107311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff adler &= 0xffff; 108311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 109311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff /* in case user likes doing a byte at a time, keep it fast */ 110311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (len == 1) { 111311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff adler += buf[0]; 112311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (adler >= BASE) 113311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff adler -= BASE; 114311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff sum2 += adler; 115311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (sum2 >= BASE) 116311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff sum2 -= BASE; 117311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff return adler | (sum2 << 16); 118311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff } 119311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 120311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff /* initial Adler-32 value (deferred check for len == 1 speed) */ 121311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (buf == Z_NULL) 122311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff return 1L; 123311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 124311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff /* in case short lengths are provided, keep it somewhat fast */ 125311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (len < 16) { 126311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff while (len--) { 127311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff adler += *buf++; 128311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff sum2 += adler; 129311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff } 130311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (adler >= BASE) 131311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff adler -= BASE; 132311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff MOD4(sum2); /* only added so many BASE's */ 133311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff return adler | (sum2 << 16); 134311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff } 135311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 136311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff /* do length NMAX blocks -- requires just one modulo operation */ 137311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff while (len >= NMAX) { 138311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff len -= NMAX; 139311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff n = NMAX / 16; /* NMAX is divisible by 16 */ 140311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff do { 141311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff DO16(buf); /* 16 sums unrolled */ 142311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff buf += 16; 143311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff } while (--n); 144311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff MOD(adler); 145311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff MOD(sum2); 146311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff } 147311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 148311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff /* do remaining bytes (less than NMAX, still just one modulo) */ 149311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (len) { /* avoid modulos if none remaining */ 150311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff while (len >= 16) { 151311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff len -= 16; 152311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff DO16(buf); 153311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff buf += 16; 154311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff } 155311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff while (len--) { 156311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff adler += *buf++; 157311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff sum2 += adler; 158311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff } 159311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff MOD(adler); 160311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff MOD(sum2); 161311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff } 162311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 163311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff /* return recombined sums */ 164311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff return adler | (sum2 << 16); 165311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff} 166311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 167311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff/* ========================================================================= */ 168311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiffuLong ZEXPORT adler32_combine(adler1, adler2, len2) 169311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff uLong adler1; 170311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff uLong adler2; 171311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff z_off_t len2; 172311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff{ 173311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff unsigned long sum1; 174311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff unsigned long sum2; 175311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff unsigned rem; 176311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff 177311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff /* the derivation of this formula is left as an exercise for the reader */ 178311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff rem = (unsigned)(len2 % BASE); 179311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff sum1 = adler1 & 0xffff; 180311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff sum2 = rem * sum1; 181311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff MOD(sum2); 182311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff sum1 += (adler2 & 0xffff) + BASE - 1; 183311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff sum2 += ((adler1 >> 16) & 0xffff) + ((adler2 >> 16) & 0xffff) + BASE - rem; 184311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (sum1 >= BASE) sum1 -= BASE; 185311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (sum1 >= BASE) sum1 -= BASE; 186311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (sum2 >= (BASE << 1)) sum2 -= (BASE << 1); 187311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff if (sum2 >= BASE) sum2 -= BASE; 188311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff return sum1 | (sum2 << 16); 189311c71486f5f6074e5ba62a7f4c5397c8700b868openvcdiff} 190