| 1,5 → 1,5 |
|---|
| /* adler32.c -- compute the Adler-32 checksum of a data stream |
| * Copyright (C) 1995-2007 Mark Adler |
| * Copyright (C) 1995-2011 Mark Adler |
| * For conditions of distribution and use, see copyright notice in zlib.h |
| */ |
| |
| 9,9 → 9,9 |
|---|
| |
| #define local static |
| |
| local uLong adler32_combine_(uLong adler1, uLong adler2, z_off64_t len2); |
| local uLong adler32_combine_ OF((uLong adler1, uLong adler2, z_off64_t len2)); |
| |
| #define BASE 65521UL /* largest prime smaller than 65536 */ |
| #define BASE 65521 /* largest prime smaller than 65536 */ |
| #define NMAX 5552 |
| /* NMAX is the largest n such that 255n(n+1)/2 + (n+1)(BASE-1) <= 2^32-1 */ |
| |
| 21,39 → 21,44 |
|---|
| #define DO8(buf,i) DO4(buf,i); DO4(buf,i+4); |
| #define DO16(buf) DO8(buf,0); DO8(buf,8); |
| |
| /* use NO_DIVIDE if your processor does not do division in hardware */ |
| /* use NO_DIVIDE if your processor does not do division in hardware -- |
| try it both ways to see which is faster */ |
| #ifdef NO_DIVIDE |
| # define MOD(a) \ |
| /* note that this assumes BASE is 65521, where 65536 % 65521 == 15 |
| (thank you to John Reiser for pointing this out) */ |
| # define CHOP(a) \ |
| do { \ |
| if (a >= (BASE << 16)) a -= (BASE << 16); \ |
| if (a >= (BASE << 15)) a -= (BASE << 15); \ |
| if (a >= (BASE << 14)) a -= (BASE << 14); \ |
| if (a >= (BASE << 13)) a -= (BASE << 13); \ |
| if (a >= (BASE << 12)) a -= (BASE << 12); \ |
| if (a >= (BASE << 11)) a -= (BASE << 11); \ |
| if (a >= (BASE << 10)) a -= (BASE << 10); \ |
| if (a >= (BASE << 9)) a -= (BASE << 9); \ |
| if (a >= (BASE << 8)) a -= (BASE << 8); \ |
| if (a >= (BASE << 7)) a -= (BASE << 7); \ |
| if (a >= (BASE << 6)) a -= (BASE << 6); \ |
| if (a >= (BASE << 5)) a -= (BASE << 5); \ |
| if (a >= (BASE << 4)) a -= (BASE << 4); \ |
| if (a >= (BASE << 3)) a -= (BASE << 3); \ |
| if (a >= (BASE << 2)) a -= (BASE << 2); \ |
| if (a >= (BASE << 1)) a -= (BASE << 1); \ |
| unsigned long tmp = a >> 16; \ |
| a &= 0xffffUL; \ |
| a += (tmp << 4) - tmp; \ |
| } while (0) |
| # define MOD28(a) \ |
| do { \ |
| CHOP(a); \ |
| if (a >= BASE) a -= BASE; \ |
| } while (0) |
| # define MOD4(a) \ |
| # define MOD(a) \ |
| do { \ |
| if (a >= (BASE << 4)) a -= (BASE << 4); \ |
| if (a >= (BASE << 3)) a -= (BASE << 3); \ |
| if (a >= (BASE << 2)) a -= (BASE << 2); \ |
| if (a >= (BASE << 1)) a -= (BASE << 1); \ |
| CHOP(a); \ |
| MOD28(a); \ |
| } while (0) |
| # define MOD63(a) \ |
| do { /* this assumes a is not negative */ \ |
| z_off64_t tmp = a >> 32; \ |
| a &= 0xffffffffL; \ |
| a += (tmp << 8) - (tmp << 5) + tmp; \ |
| tmp = a >> 16; \ |
| a &= 0xffffL; \ |
| a += (tmp << 4) - tmp; \ |
| tmp = a >> 16; \ |
| a &= 0xffffL; \ |
| a += (tmp << 4) - tmp; \ |
| if (a >= BASE) a -= BASE; \ |
| } while (0) |
| #else |
| # define MOD(a) a %= BASE |
| # define MOD4(a) a %= BASE |
| # define MOD28(a) a %= BASE |
| # define MOD63(a) a %= BASE |
| #endif |
| |
| /* ========================================================================= */ |
| 92,7 → 97,7 |
|---|
| } |
| if (adler >= BASE) |
| adler -= BASE; |
| MOD4(sum2); /* only added so many BASE's */ |
| MOD28(sum2); /* only added so many BASE's */ |
| return adler | (sum2 << 16); |
| } |
| |
| 137,8 → 142,13 |
|---|
| unsigned long sum2; |
| unsigned rem; |
| |
| /* for negative len, return invalid adler32 as a clue for debugging */ |
| if (len2 < 0) |
| return 0xffffffffUL; |
| |
| /* the derivation of this formula is left as an exercise for the reader */ |
| rem = (unsigned)(len2 % BASE); |
| MOD63(len2); /* assumes len2 >= 0 */ |
| rem = (unsigned)len2; |
| sum1 = adler1 & 0xffff; |
| sum2 = rem * sum1; |
| MOD(sum2); |