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comparison: security/nss/lib/zlib/adler32.c
security/nss/lib/zlib/adler32.c
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- TOR_BUG_9701
- changeset 15
- b8a032363ba2
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| -1:000000000000 | 0:a7824c0bcac3 |
|---|---|
| 1 /* adler32.c -- compute the Adler-32 checksum of a data stream | |
| 2 * Copyright (C) 1995-2007 Mark Adler | |
| 3 * For conditions of distribution and use, see copyright notice in zlib.h | |
| 4 */ | |
| 5 | |
| 6 /* @(#) $Id$ */ | |
| 7 | |
| 8 #include "zutil.h" | |
| 9 | |
| 10 #define local static | |
| 11 | |
| 12 local uLong adler32_combine_(uLong adler1, uLong adler2, z_off64_t len2); | |
| 13 | |
| 14 #define BASE 65521UL /* largest prime smaller than 65536 */ | |
| 15 #define NMAX 5552 | |
| 16 /* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */ | |
| 17 | |
| 18 #define DO1(buf,i) {adler += (buf)[i]; sum2 += adler;} | |
| 19 #define DO2(buf,i) DO1(buf,i); DO1(buf,i+1); | |
| 20 #define DO4(buf,i) DO2(buf,i); DO2(buf,i+2); | |
| 21 #define DO8(buf,i) DO4(buf,i); DO4(buf,i+4); | |
| 22 #define DO16(buf) DO8(buf,0); DO8(buf,8); | |
| 23 | |
| 24 /* use NO_DIVIDE if your processor does not do division in hardware */ | |
| 25 #ifdef NO_DIVIDE | |
| 26 # define MOD(a) \ | |
| 27 do { \ | |
| 28 if (a >= (BASE << 16)) a -= (BASE << 16); \ | |
| 29 if (a >= (BASE << 15)) a -= (BASE << 15); \ | |
| 30 if (a >= (BASE << 14)) a -= (BASE << 14); \ | |
| 31 if (a >= (BASE << 13)) a -= (BASE << 13); \ | |
| 32 if (a >= (BASE << 12)) a -= (BASE << 12); \ | |
| 33 if (a >= (BASE << 11)) a -= (BASE << 11); \ | |
| 34 if (a >= (BASE << 10)) a -= (BASE << 10); \ | |
| 35 if (a >= (BASE << 9)) a -= (BASE << 9); \ | |
| 36 if (a >= (BASE << 8)) a -= (BASE << 8); \ | |
| 37 if (a >= (BASE << 7)) a -= (BASE << 7); \ | |
| 38 if (a >= (BASE << 6)) a -= (BASE << 6); \ | |
| 39 if (a >= (BASE << 5)) a -= (BASE << 5); \ | |
| 40 if (a >= (BASE << 4)) a -= (BASE << 4); \ | |
| 41 if (a >= (BASE << 3)) a -= (BASE << 3); \ | |
| 42 if (a >= (BASE << 2)) a -= (BASE << 2); \ | |
| 43 if (a >= (BASE << 1)) a -= (BASE << 1); \ | |
| 44 if (a >= BASE) a -= BASE; \ | |
| 45 } while (0) | |
| 46 # define MOD4(a) \ | |
| 47 do { \ | |
| 48 if (a >= (BASE << 4)) a -= (BASE << 4); \ | |
| 49 if (a >= (BASE << 3)) a -= (BASE << 3); \ | |
| 50 if (a >= (BASE << 2)) a -= (BASE << 2); \ | |
| 51 if (a >= (BASE << 1)) a -= (BASE << 1); \ | |
| 52 if (a >= BASE) a -= BASE; \ | |
| 53 } while (0) | |
| 54 #else | |
| 55 # define MOD(a) a %= BASE | |
| 56 # define MOD4(a) a %= BASE | |
| 57 #endif | |
| 58 | |
| 59 /* ========================================================================= */ | |
| 60 uLong ZEXPORT adler32(adler, buf, len) | |
| 61 uLong adler; | |
| 62 const Bytef *buf; | |
| 63 uInt len; | |
| 64 { | |
| 65 unsigned long sum2; | |
| 66 unsigned n; | |
| 67 | |
| 68 /* split Adler-32 into component sums */ | |
| 69 sum2 = (adler >> 16) & 0xffff; | |
| 70 adler &= 0xffff; | |
| 71 | |
| 72 /* in case user likes doing a byte at a time, keep it fast */ | |
| 73 if (len == 1) { | |
| 74 adler += buf[0]; | |
| 75 if (adler >= BASE) | |
| 76 adler -= BASE; | |
| 77 sum2 += adler; | |
| 78 if (sum2 >= BASE) | |
| 79 sum2 -= BASE; | |
| 80 return adler | (sum2 << 16); | |
| 81 } | |
| 82 | |
| 83 /* initial Adler-32 value (deferred check for len == 1 speed) */ | |
| 84 if (buf == Z_NULL) | |
| 85 return 1L; | |
| 86 | |
| 87 /* in case short lengths are provided, keep it somewhat fast */ | |
| 88 if (len < 16) { | |
| 89 while (len--) { | |
| 90 adler += *buf++; | |
| 91 sum2 += adler; | |
| 92 } | |
| 93 if (adler >= BASE) | |
| 94 adler -= BASE; | |
| 95 MOD4(sum2); /* only added so many BASE's */ | |
| 96 return adler | (sum2 << 16); | |
| 97 } | |
| 98 | |
| 99 /* do length NMAX blocks -- requires just one modulo operation */ | |
| 100 while (len >= NMAX) { | |
| 101 len -= NMAX; | |
| 102 n = NMAX / 16; /* NMAX is divisible by 16 */ | |
| 103 do { | |
| 104 DO16(buf); /* 16 sums unrolled */ | |
| 105 buf += 16; | |
| 106 } while (--n); | |
| 107 MOD(adler); | |
| 108 MOD(sum2); | |
| 109 } | |
| 110 | |
| 111 /* do remaining bytes (less than NMAX, still just one modulo) */ | |
| 112 if (len) { /* avoid modulos if none remaining */ | |
| 113 while (len >= 16) { | |
| 114 len -= 16; | |
| 115 DO16(buf); | |
| 116 buf += 16; | |
| 117 } | |
| 118 while (len--) { | |
| 119 adler += *buf++; | |
| 120 sum2 += adler; | |
| 121 } | |
| 122 MOD(adler); | |
| 123 MOD(sum2); | |
| 124 } | |
| 125 | |
| 126 /* return recombined sums */ | |
| 127 return adler | (sum2 << 16); | |
| 128 } | |
| 129 | |
| 130 /* ========================================================================= */ | |
| 131 local uLong adler32_combine_(adler1, adler2, len2) | |
| 132 uLong adler1; | |
| 133 uLong adler2; | |
| 134 z_off64_t len2; | |
| 135 { | |
| 136 unsigned long sum1; | |
| 137 unsigned long sum2; | |
| 138 unsigned rem; | |
| 139 | |
| 140 /* the derivation of this formula is left as an exercise for the reader */ | |
| 141 rem = (unsigned)(len2 % BASE); | |
| 142 sum1 = adler1 & 0xffff; | |
| 143 sum2 = rem * sum1; | |
| 144 MOD(sum2); | |
| 145 sum1 += (adler2 & 0xffff) + BASE - 1; | |
| 146 sum2 += ((adler1 >> 16) & 0xffff) + ((adler2 >> 16) & 0xffff) + BASE - rem; | |
| 147 if (sum1 >= BASE) sum1 -= BASE; | |
| 148 if (sum1 >= BASE) sum1 -= BASE; | |
| 149 if (sum2 >= (BASE << 1)) sum2 -= (BASE << 1); | |
| 150 if (sum2 >= BASE) sum2 -= BASE; | |
| 151 return sum1 | (sum2 << 16); | |
| 152 } | |
| 153 | |
| 154 /* ========================================================================= */ | |
| 155 uLong ZEXPORT adler32_combine(adler1, adler2, len2) | |
| 156 uLong adler1; | |
| 157 uLong adler2; | |
| 158 z_off_t len2; | |
| 159 { | |
| 160 return adler32_combine_(adler1, adler2, len2); | |
| 161 } | |
| 162 | |
| 163 uLong ZEXPORT adler32_combine64(adler1, adler2, len2) | |
| 164 uLong adler1; | |
| 165 uLong adler2; | |
| 166 z_off64_t len2; | |
| 167 { | |
| 168 return adler32_combine_(adler1, adler2, len2); | |
| 169 } |
