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Diffstat (limited to 'libpng/adler32.c')
| -rw-r--r-- | libpng/adler32.c | 149 |
1 files changed, 0 insertions, 149 deletions
diff --git a/libpng/adler32.c b/libpng/adler32.c deleted file mode 100644 index 007ba26..0000000 --- a/libpng/adler32.c +++ /dev/null @@ -1,149 +0,0 @@ -/* adler32.c -- compute the Adler-32 checksum of a data stream - * Copyright (C) 1995-2004 Mark Adler - * For conditions of distribution and use, see copyright notice in zlib.h - */ - -/* @(#) $Id$ */ - -#define ZLIB_INTERNAL -#include "zlib.h" - -#define BASE 65521UL /* 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 */ - -#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); - -/* use NO_DIVIDE if your processor does not do division in hardware */ -#ifdef NO_DIVIDE -# define MOD(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); \ - if (a >= BASE) a -= BASE; \ - } while (0) -# define MOD4(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); \ - if (a >= BASE) a -= BASE; \ - } while (0) -#else -# define MOD(a) a %= BASE -# define MOD4(a) a %= BASE -#endif - -/* ========================================================================= */ -uLong ZEXPORT adler32(adler, buf, len) - uLong adler; - const Bytef *buf; - uInt len; -{ - unsigned long sum2; - unsigned n; - - /* split Adler-32 into component sums */ - sum2 = (adler >> 16) & 0xffff; - adler &= 0xffff; - - /* in case user likes doing a byte at a time, keep it fast */ - if (len == 1) { - adler += buf[0]; - if (adler >= BASE) - adler -= BASE; - sum2 += adler; - if (sum2 >= BASE) - sum2 -= BASE; - return adler | (sum2 << 16); - } - - /* initial Adler-32 value (deferred check for len == 1 speed) */ - if (buf == Z_NULL) - return 1L; - - /* in case short lengths are provided, keep it somewhat fast */ - if (len < 16) { - while (len--) { - adler += *buf++; - sum2 += adler; - } - if (adler >= BASE) - adler -= BASE; - MOD4(sum2); /* only added so many BASE's */ - return adler | (sum2 << 16); - } - - /* do length NMAX blocks -- requires just one modulo operation */ - while (len >= NMAX) { - len -= NMAX; - n = NMAX / 16; /* NMAX is divisible by 16 */ - do { - DO16(buf); /* 16 sums unrolled */ - buf += 16; - } while (--n); - MOD(adler); - MOD(sum2); - } - - /* do remaining bytes (less than NMAX, still just one modulo) */ - if (len) { /* avoid modulos if none remaining */ - while (len >= 16) { - len -= 16; - DO16(buf); - buf += 16; - } - while (len--) { - adler += *buf++; - sum2 += adler; - } - MOD(adler); - MOD(sum2); - } - - /* return recombined sums */ - return adler | (sum2 << 16); -} - -/* ========================================================================= */ -uLong ZEXPORT adler32_combine(adler1, adler2, len2) - uLong adler1; - uLong adler2; - z_off_t len2; -{ - unsigned long sum1; - unsigned long sum2; - unsigned rem; - - /* the derivation of this formula is left as an exercise for the reader */ - rem = (unsigned)(len2 % BASE); - sum1 = adler1 & 0xffff; - sum2 = rem * sum1; - MOD(sum2); - sum1 += (adler2 & 0xffff) + BASE - 1; - sum2 += ((adler1 >> 16) & 0xffff) + ((adler2 >> 16) & 0xffff) + BASE - rem; - if (sum1 > BASE) sum1 -= BASE; - if (sum1 > BASE) sum1 -= BASE; - if (sum2 > (BASE << 1)) sum2 -= (BASE << 1); - if (sum2 > BASE) sum2 -= BASE; - return sum1 | (sum2 << 16); -} |