Index: third_party/zlib/adler32.c |
diff --git a/third_party/zlib/adler32.c b/third_party/zlib/adler32.c |
index 65ad6a5adc44c00428b35eb15ff26d16f9ef209b..a868f073d8a0e35dcb3ec812b41b1d3f0acdd84d 100644 |
--- a/third_party/zlib/adler32.c |
+++ b/third_party/zlib/adler32.c |
@@ -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 @@ local uLong adler32_combine_(uLong adler1, uLong adler2, z_off64_t len2); |
#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 { \ |
+ unsigned long tmp = a >> 16; \ |
+ a &= 0xffffUL; \ |
+ a += (tmp << 4) - tmp; \ |
+ } while (0) |
+# define MOD28(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); \ |
+ 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 @@ uLong ZEXPORT adler32(adler, buf, len) |
} |
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 @@ local uLong adler32_combine_(adler1, adler2, len2) |
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); |