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comparison: modules/zlib/src/adler32.c
modules/zlib/src/adler32.c
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- TOR_BUG_9701
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| -1:000000000000 | 0:91a7918da9f3 |
|---|---|
| 1 /* adler32.c -- compute the Adler-32 checksum of a data stream | |
| 2 * Copyright (C) 1995-2011 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_ OF((uLong adler1, uLong adler2, z_off64_t len2)); | |
| 13 | |
| 14 #define BASE 65521 /* 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 try it both ways to see which is faster */ | |
| 26 #ifdef NO_DIVIDE | |
| 27 /* note that this assumes BASE is 65521, where 65536 % 65521 == 15 | |
| 28 (thank you to John Reiser for pointing this out) */ | |
| 29 # define CHOP(a) \ | |
| 30 do { \ | |
| 31 unsigned long tmp = a >> 16; \ | |
| 32 a &= 0xffffUL; \ | |
| 33 a += (tmp << 4) - tmp; \ | |
| 34 } while (0) | |
| 35 # define MOD28(a) \ | |
| 36 do { \ | |
| 37 CHOP(a); \ | |
| 38 if (a >= BASE) a -= BASE; \ | |
| 39 } while (0) | |
| 40 # define MOD(a) \ | |
| 41 do { \ | |
| 42 CHOP(a); \ | |
| 43 MOD28(a); \ | |
| 44 } while (0) | |
| 45 # define MOD63(a) \ | |
| 46 do { /* this assumes a is not negative */ \ | |
| 47 z_off64_t tmp = a >> 32; \ | |
| 48 a &= 0xffffffffL; \ | |
| 49 a += (tmp << 8) - (tmp << 5) + tmp; \ | |
| 50 tmp = a >> 16; \ | |
| 51 a &= 0xffffL; \ | |
| 52 a += (tmp << 4) - tmp; \ | |
| 53 tmp = a >> 16; \ | |
| 54 a &= 0xffffL; \ | |
| 55 a += (tmp << 4) - tmp; \ | |
| 56 if (a >= BASE) a -= BASE; \ | |
| 57 } while (0) | |
| 58 #else | |
| 59 # define MOD(a) a %= BASE | |
| 60 # define MOD28(a) a %= BASE | |
| 61 # define MOD63(a) a %= BASE | |
| 62 #endif | |
| 63 | |
| 64 /* ========================================================================= */ | |
| 65 uLong ZEXPORT adler32(adler, buf, len) | |
| 66 uLong adler; | |
| 67 const Bytef *buf; | |
| 68 uInt len; | |
| 69 { | |
| 70 unsigned long sum2; | |
| 71 unsigned n; | |
| 72 | |
| 73 /* split Adler-32 into component sums */ | |
| 74 sum2 = (adler >> 16) & 0xffff; | |
| 75 adler &= 0xffff; | |
| 76 | |
| 77 /* in case user likes doing a byte at a time, keep it fast */ | |
| 78 if (len == 1) { | |
| 79 adler += buf[0]; | |
| 80 if (adler >= BASE) | |
| 81 adler -= BASE; | |
| 82 sum2 += adler; | |
| 83 if (sum2 >= BASE) | |
| 84 sum2 -= BASE; | |
| 85 return adler | (sum2 << 16); | |
| 86 } | |
| 87 | |
| 88 /* initial Adler-32 value (deferred check for len == 1 speed) */ | |
| 89 if (buf == Z_NULL) | |
| 90 return 1L; | |
| 91 | |
| 92 /* in case short lengths are provided, keep it somewhat fast */ | |
| 93 if (len < 16) { | |
| 94 while (len--) { | |
| 95 adler += *buf++; | |
| 96 sum2 += adler; | |
| 97 } | |
| 98 if (adler >= BASE) | |
| 99 adler -= BASE; | |
| 100 MOD28(sum2); /* only added so many BASE's */ | |
| 101 return adler | (sum2 << 16); | |
| 102 } | |
| 103 | |
| 104 /* do length NMAX blocks -- requires just one modulo operation */ | |
| 105 while (len >= NMAX) { | |
| 106 len -= NMAX; | |
| 107 n = NMAX / 16; /* NMAX is divisible by 16 */ | |
| 108 do { | |
| 109 DO16(buf); /* 16 sums unrolled */ | |
| 110 buf += 16; | |
| 111 } while (--n); | |
| 112 MOD(adler); | |
| 113 MOD(sum2); | |
| 114 } | |
| 115 | |
| 116 /* do remaining bytes (less than NMAX, still just one modulo) */ | |
| 117 if (len) { /* avoid modulos if none remaining */ | |
| 118 while (len >= 16) { | |
| 119 len -= 16; | |
| 120 DO16(buf); | |
| 121 buf += 16; | |
| 122 } | |
| 123 while (len--) { | |
| 124 adler += *buf++; | |
| 125 sum2 += adler; | |
| 126 } | |
| 127 MOD(adler); | |
| 128 MOD(sum2); | |
| 129 } | |
| 130 | |
| 131 /* return recombined sums */ | |
| 132 return adler | (sum2 << 16); | |
| 133 } | |
| 134 | |
| 135 /* ========================================================================= */ | |
| 136 local uLong adler32_combine_(adler1, adler2, len2) | |
| 137 uLong adler1; | |
| 138 uLong adler2; | |
| 139 z_off64_t len2; | |
| 140 { | |
| 141 unsigned long sum1; | |
| 142 unsigned long sum2; | |
| 143 unsigned rem; | |
| 144 | |
| 145 /* for negative len, return invalid adler32 as a clue for debugging */ | |
| 146 if (len2 < 0) | |
| 147 return 0xffffffffUL; | |
| 148 | |
| 149 /* the derivation of this formula is left as an exercise for the reader */ | |
| 150 MOD63(len2); /* assumes len2 >= 0 */ | |
| 151 rem = (unsigned)len2; | |
| 152 sum1 = adler1 & 0xffff; | |
| 153 sum2 = rem * sum1; | |
| 154 MOD(sum2); | |
| 155 sum1 += (adler2 & 0xffff) + BASE - 1; | |
| 156 sum2 += ((adler1 >> 16) & 0xffff) + ((adler2 >> 16) & 0xffff) + BASE - rem; | |
| 157 if (sum1 >= BASE) sum1 -= BASE; | |
| 158 if (sum1 >= BASE) sum1 -= BASE; | |
| 159 if (sum2 >= (BASE << 1)) sum2 -= (BASE << 1); | |
| 160 if (sum2 >= BASE) sum2 -= BASE; | |
| 161 return sum1 | (sum2 << 16); | |
| 162 } | |
| 163 | |
| 164 /* ========================================================================= */ | |
| 165 uLong ZEXPORT adler32_combine(adler1, adler2, len2) | |
| 166 uLong adler1; | |
| 167 uLong adler2; | |
| 168 z_off_t len2; | |
| 169 { | |
| 170 return adler32_combine_(adler1, adler2, len2); | |
| 171 } | |
| 172 | |
| 173 uLong ZEXPORT adler32_combine64(adler1, adler2, len2) | |
| 174 uLong adler1; | |
| 175 uLong adler2; | |
| 176 z_off64_t len2; | |
| 177 { | |
| 178 return adler32_combine_(adler1, adler2, len2); | |
| 179 } |
