Update Zlib to version 1.2.8

third_party/zlib/adler32.c

 /* 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
  */
 
 /* @(#) $Id$ */
 
 #include "zutil.h"
 
 #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 */
 
 #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 */
+/* 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 { \
-        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; \
+        CHOP(a); \
+        MOD28(a); \
     } 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); \
+#  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
 
 /* ========================================================================= */
 uLong ZEXPORT adler32(adler, buf, len)
     uLong adler;
     const Bytef *buf;
     uInt len;
 {
     unsigned long sum2;
     unsigned n;
@@ skipping 18 matching lines @@
         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 */
+        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;
@@ skipping 24 matching lines @@
 /* ========================================================================= */
 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 */
-    rem = (unsigned)(len2 % BASE);
+    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 >= (BASE << 1)) sum2 -= (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);
 }