1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/compiler-init/zlib/adler32.c Sat Jul 15 04:51:28 2006 +0000
1.3 @@ -0,0 +1,149 @@
1.4 +/* adler32.c -- compute the Adler-32 checksum of a data stream
1.5 + * Copyright (C) 1995-2004 Mark Adler
1.6 + * For conditions of distribution and use, see copyright notice in zlib.h
1.7 + */
1.8 +
1.9 +/* @(#) $Id$ */
1.10 +
1.11 +#define ZLIB_INTERNAL
1.12 +#include "zlib.h"
1.13 +
1.14 +#define BASE 65521UL /* largest prime smaller than 65536 */
1.15 +#define NMAX 5552
1.16 +/* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */
1.17 +
1.18 +#define DO1(buf,i) {adler += (buf)[i]; sum2 += adler;}
1.19 +#define DO2(buf,i) DO1(buf,i); DO1(buf,i+1);
1.20 +#define DO4(buf,i) DO2(buf,i); DO2(buf,i+2);
1.21 +#define DO8(buf,i) DO4(buf,i); DO4(buf,i+4);
1.22 +#define DO16(buf) DO8(buf,0); DO8(buf,8);
1.23 +
1.24 +/* use NO_DIVIDE if your processor does not do division in hardware */
1.25 +#ifdef NO_DIVIDE
1.26 +# define MOD(a) \
1.27 + do { \
1.28 + if (a >= (BASE << 16)) a -= (BASE << 16); \
1.29 + if (a >= (BASE << 15)) a -= (BASE << 15); \
1.30 + if (a >= (BASE << 14)) a -= (BASE << 14); \
1.31 + if (a >= (BASE << 13)) a -= (BASE << 13); \
1.32 + if (a >= (BASE << 12)) a -= (BASE << 12); \
1.33 + if (a >= (BASE << 11)) a -= (BASE << 11); \
1.34 + if (a >= (BASE << 10)) a -= (BASE << 10); \
1.35 + if (a >= (BASE << 9)) a -= (BASE << 9); \
1.36 + if (a >= (BASE << 8)) a -= (BASE << 8); \
1.37 + if (a >= (BASE << 7)) a -= (BASE << 7); \
1.38 + if (a >= (BASE << 6)) a -= (BASE << 6); \
1.39 + if (a >= (BASE << 5)) a -= (BASE << 5); \
1.40 + if (a >= (BASE << 4)) a -= (BASE << 4); \
1.41 + if (a >= (BASE << 3)) a -= (BASE << 3); \
1.42 + if (a >= (BASE << 2)) a -= (BASE << 2); \
1.43 + if (a >= (BASE << 1)) a -= (BASE << 1); \
1.44 + if (a >= BASE) a -= BASE; \
1.45 + } while (0)
1.46 +# define MOD4(a) \
1.47 + do { \
1.48 + if (a >= (BASE << 4)) a -= (BASE << 4); \
1.49 + if (a >= (BASE << 3)) a -= (BASE << 3); \
1.50 + if (a >= (BASE << 2)) a -= (BASE << 2); \
1.51 + if (a >= (BASE << 1)) a -= (BASE << 1); \
1.52 + if (a >= BASE) a -= BASE; \
1.53 + } while (0)
1.54 +#else
1.55 +# define MOD(a) a %= BASE
1.56 +# define MOD4(a) a %= BASE
1.57 +#endif
1.58 +
1.59 +/* ========================================================================= */
1.60 +uLong ZEXPORT adler32(adler, buf, len)
1.61 + uLong adler;
1.62 + const Bytef *buf;
1.63 + uInt len;
1.64 +{
1.65 + unsigned long sum2;
1.66 + unsigned n;
1.67 +
1.68 + /* split Adler-32 into component sums */
1.69 + sum2 = (adler >> 16) & 0xffff;
1.70 + adler &= 0xffff;
1.71 +
1.72 + /* in case user likes doing a byte at a time, keep it fast */
1.73 + if (len == 1) {
1.74 + adler += buf[0];
1.75 + if (adler >= BASE)
1.76 + adler -= BASE;
1.77 + sum2 += adler;
1.78 + if (sum2 >= BASE)
1.79 + sum2 -= BASE;
1.80 + return adler | (sum2 << 16);
1.81 + }
1.82 +
1.83 + /* initial Adler-32 value (deferred check for len == 1 speed) */
1.84 + if (buf == Z_NULL)
1.85 + return 1L;
1.86 +
1.87 + /* in case short lengths are provided, keep it somewhat fast */
1.88 + if (len < 16) {
1.89 + while (len--) {
1.90 + adler += *buf++;
1.91 + sum2 += adler;
1.92 + }
1.93 + if (adler >= BASE)
1.94 + adler -= BASE;
1.95 + MOD4(sum2); /* only added so many BASE's */
1.96 + return adler | (sum2 << 16);
1.97 + }
1.98 +
1.99 + /* do length NMAX blocks -- requires just one modulo operation */
1.100 + while (len >= NMAX) {
1.101 + len -= NMAX;
1.102 + n = NMAX / 16; /* NMAX is divisible by 16 */
1.103 + do {
1.104 + DO16(buf); /* 16 sums unrolled */
1.105 + buf += 16;
1.106 + } while (--n);
1.107 + MOD(adler);
1.108 + MOD(sum2);
1.109 + }
1.110 +
1.111 + /* do remaining bytes (less than NMAX, still just one modulo) */
1.112 + if (len) { /* avoid modulos if none remaining */
1.113 + while (len >= 16) {
1.114 + len -= 16;
1.115 + DO16(buf);
1.116 + buf += 16;
1.117 + }
1.118 + while (len--) {
1.119 + adler += *buf++;
1.120 + sum2 += adler;
1.121 + }
1.122 + MOD(adler);
1.123 + MOD(sum2);
1.124 + }
1.125 +
1.126 + /* return recombined sums */
1.127 + return adler | (sum2 << 16);
1.128 +}
1.129 +
1.130 +/* ========================================================================= */
1.131 +uLong ZEXPORT adler32_combine(adler1, adler2, len2)
1.132 + uLong adler1;
1.133 + uLong adler2;
1.134 + z_off_t len2;
1.135 +{
1.136 + unsigned long sum1;
1.137 + unsigned long sum2;
1.138 + unsigned rem;
1.139 +
1.140 + /* the derivation of this formula is left as an exercise for the reader */
1.141 + rem = (unsigned)(len2 % BASE);
1.142 + sum1 = adler1 & 0xffff;
1.143 + sum2 = rem * sum1;
1.144 + MOD(sum2);
1.145 + sum1 += (adler2 & 0xffff) + BASE - 1;
1.146 + sum2 += ((adler1 >> 16) & 0xffff) + ((adler2 >> 16) & 0xffff) + BASE - rem;
1.147 + if (sum1 > BASE) sum1 -= BASE;
1.148 + if (sum1 > BASE) sum1 -= BASE;
1.149 + if (sum2 > (BASE << 1)) sum2 -= (BASE << 1);
1.150 + if (sum2 > BASE) sum2 -= BASE;
1.151 + return sum1 | (sum2 << 16);
1.152 +}
