1 files changed, 28 insertions, 3 deletions

diff --git a/adler32.c b/adler32.c
index 4d52399..bad930e 100644
--- a/adler32.c
+++ b/adler32.c
@@ -8,7 +8,7 @@
 #define ZLIB_INTERNAL
 #include "zlib.h"
 
-#define BASE 65521L /* largest prime smaller than 65536 */
+#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 */
 
@@ -18,6 +18,31 @@
 #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;
@@ -42,8 +67,8 @@ uLong ZEXPORT adler32(adler, buf, len)
             s1 += *buf++;
             s2 += s1;
         } while (--k);
-        s1 %= BASE;
-        s2 %= BASE;
+        MOD(s1);
+        MOD(s2);
     }
     return (s2 << 16) | s1;
 }