diff options
Diffstat (limited to 'zlib/adler32.c')
-rw-r--r-- | zlib/adler32.c | 260 |
1 files changed, 186 insertions, 74 deletions
diff --git a/zlib/adler32.c b/zlib/adler32.c index dd6d60f..d0be438 100644 --- a/zlib/adler32.c +++ b/zlib/adler32.c @@ -1,74 +1,186 @@ -/* adler32.c -- compute the Adler-32 checksum of a data stream
- * Copyright (C) 1995-2003 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) {s1 += buf[i]; s2 += s1;}
-#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);
-
-#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)
-#else
-# define MOD(a) a %= BASE
-#endif
-
-/* ========================================================================= */
-uLong ZEXPORT adler32(adler, buf, len)
- uLong adler;
- const Bytef *buf;
- uInt len;
-{
- unsigned long s1 = adler & 0xffff;
- unsigned long s2 = (adler >> 16) & 0xffff;
- int k;
-
- if (buf == Z_NULL) return 1L;
-
- while (len > 0) {
- k = len < NMAX ? (int)len : NMAX;
- len -= k;
- while (k >= 16) {
- DO16(buf);
- buf += 16;
- k -= 16;
- }
- if (k != 0) do {
- s1 += *buf++;
- s2 += s1;
- } while (--k);
- MOD(s1);
- MOD(s2);
- }
- return (s2 << 16) | s1;
-}
+/* adler32.c -- compute the Adler-32 checksum of a data stream + * Copyright (C) 1995-2011, 2016 Mark Adler + * For conditions of distribution and use, see copyright notice in zlib.h + */ + +/* @(#) $Id$ */ + +#include "zutil.h" + +local uLong adler32_combine_ OF((uLong adler1, uLong adler2, z_off64_t len2)); + +#define BASE 65521U /* 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 -- + try it both ways to see which is faster */ +#ifdef NO_DIVIDE +/* note that this assumes BASE is 65521, where 65536 % 65521 == 15 + (thank you to John Reiser for pointing this out) */ +# define CHOP(a) \ + do { \ + 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 MOD(a) \ + do { \ + 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 MOD28(a) a %= BASE +# define MOD63(a) a %= BASE +#endif + +/* ========================================================================= */ +uLong ZEXPORT adler32_z(adler, buf, len) + uLong adler; + const Bytef *buf; + z_size_t 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; + MOD28(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(adler, buf, len) + uLong adler; + const Bytef *buf; + uInt len; +{ + return adler32_z(adler, buf, len); +} + +/* ========================================================================= */ +local uLong adler32_combine_(adler1, adler2, len2) + uLong adler1; + uLong adler2; + z_off64_t len2; +{ + unsigned long sum1; + 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 */ + MOD63(len2); /* assumes len2 >= 0 */ + rem = (unsigned)len2; + 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 >= ((unsigned long)BASE << 1)) sum2 -= ((unsigned long)BASE << 1); + if (sum2 >= BASE) sum2 -= BASE; + return sum1 | (sum2 << 16); +} + +/* ========================================================================= */ +uLong ZEXPORT adler32_combine(adler1, adler2, len2) + uLong adler1; + uLong adler2; + z_off_t len2; +{ + return adler32_combine_(adler1, adler2, len2); +} + +uLong ZEXPORT adler32_combine64(adler1, adler2, len2) + uLong adler1; + uLong adler2; + z_off64_t len2; +{ + return adler32_combine_(adler1, adler2, len2); +} |