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mysql/src/5.1-dbg/zlib/adler32.c File Reference
#include "zlib.h"Include dependency graph for adler32.c:
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Defines | |
| #define | ZLIB_INTERNAL |
| #define | BASE 65521UL |
| #define | NMAX 5552 |
| #define | DO1(buf, i) {adler += (buf)[i]; sum2 += adler;} |
| #define | DO2(buf, i) DO1(buf,i); DO1(buf,i+1); |
| #define | DO4(buf, i) DO2(buf,i); DO2(buf,i+2); |
| #define | DO8(buf, i) DO4(buf,i); DO4(buf,i+4); |
| #define | DO16(buf) DO8(buf,0); DO8(buf,8); |
| #define | MOD(a) a %= BASE |
| #define | MOD4(a) a %= BASE |
Functions | |
| uLong ZEXPORT | adler32 (uLong adler, const Bytef *buf, uInt len) |
| uLong ZEXPORT | adler32_combine (uLong adler1, uLong adler2, z_off_t len2) |
Define Documentation
| #define BASE 65521UL |
| #define MOD | ( | a | ) | a %= BASE |
Function Documentation
Definition at line 57 of file adler32.c.
References BASE, DO16, MOD, MOD4, n, NMAX, and Z_NULL.
Referenced by deflate(), deflateReset(), deflateSetDictionary(), inflateSetDictionary(), and read_buf().
00061 { 00062 unsigned long sum2; 00063 unsigned n; 00064 00065 /* split Adler-32 into component sums */ 00066 sum2 = (adler >> 16) & 0xffff; 00067 adler &= 0xffff; 00068 00069 /* in case user likes doing a byte at a time, keep it fast */ 00070 if (len == 1) { 00071 adler += buf[0]; 00072 if (adler >= BASE) 00073 adler -= BASE; 00074 sum2 += adler; 00075 if (sum2 >= BASE) 00076 sum2 -= BASE; 00077 return adler | (sum2 << 16); 00078 } 00079 00080 /* initial Adler-32 value (deferred check for len == 1 speed) */ 00081 if (buf == Z_NULL) 00082 return 1L; 00083 00084 /* in case short lengths are provided, keep it somewhat fast */ 00085 if (len < 16) { 00086 while (len--) { 00087 adler += *buf++; 00088 sum2 += adler; 00089 } 00090 if (adler >= BASE) 00091 adler -= BASE; 00092 MOD4(sum2); /* only added so many BASE's */ 00093 return adler | (sum2 << 16); 00094 } 00095 00096 /* do length NMAX blocks -- requires just one modulo operation */ 00097 while (len >= NMAX) { 00098 len -= NMAX; 00099 n = NMAX / 16; /* NMAX is divisible by 16 */ 00100 do { 00101 DO16(buf); /* 16 sums unrolled */ 00102 buf += 16; 00103 } while (--n); 00104 MOD(adler); 00105 MOD(sum2); 00106 } 00107 00108 /* do remaining bytes (less than NMAX, still just one modulo) */ 00109 if (len) { /* avoid modulos if none remaining */ 00110 while (len >= 16) { 00111 len -= 16; 00112 DO16(buf); 00113 buf += 16; 00114 } 00115 while (len--) { 00116 adler += *buf++; 00117 sum2 += adler; 00118 } 00119 MOD(adler); 00120 MOD(sum2); 00121 } 00122 00123 /* return recombined sums */ 00124 return adler | (sum2 << 16); 00125 }
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Definition at line 128 of file adler32.c.
00132 { 00133 unsigned long sum1; 00134 unsigned long sum2; 00135 unsigned rem; 00136 00137 /* the derivation of this formula is left as an exercise for the reader */ 00138 rem = (unsigned)(len2 % BASE); 00139 sum1 = adler1 & 0xffff; 00140 sum2 = rem * sum1; 00141 MOD(sum2); 00142 sum1 += (adler2 & 0xffff) + BASE - 1; 00143 sum2 += ((adler1 >> 16) & 0xffff) + ((adler2 >> 16) & 0xffff) + BASE - rem; 00144 if (sum1 > BASE) sum1 -= BASE; 00145 if (sum1 > BASE) sum1 -= BASE; 00146 if (sum2 > (BASE << 1)) sum2 -= (BASE << 1); 00147 if (sum2 > BASE) sum2 -= BASE; 00148 return sum1 | (sum2 << 16); 00149 }
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