michael subversion
Thu Jul 20 10:34:02 CEST 2006

```Author: michael
Date: Thu Jul 20 10:34:01 2006
New Revision: 5800

Modified:

Log:
simpler, smaller and faster

==============================================================================
+++ trunk/libavutil/adler32.c	Thu Jul 20 10:34:01 2006
@@ -7,8 +7,6 @@

#define BASE 65521L /* 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)  {s1 += *buf++; s2 += s1;}
#define DO4(buf)  DO1(buf); DO1(buf); DO1(buf); DO1(buf);
@@ -17,22 +15,39 @@
{
unsigned long s1 = adler & 0xffff;
-    unsigned long s2 = (adler >> 16) & 0xffff;
+    unsigned long s2 = adler >> 16;

-    while (len > 0) {
-        int k = FFMIN(len, NMAX);
-        len -= k;
-#ifndef CONFIG_SMALL
-        while (k >= 16) {
-            DO16(buf);
-            k -= 16;
-        }
+    while (len>0) {
+#ifdef CONFIG_SMALL
+        while(len>4 && s2 < (1U<<31)){
+            DO4(buf); len-=4;
+#else
+        while(len>16 && s2 < (1U<<31)){
+            DO16(buf); len-=16;
#endif
-        while(k--) {
-            DO1(buf);
}
+        DO1(buf); len--;
s1 %= BASE;
s2 %= BASE;
}
return (s2 << 16) | s1;
}
+
+#ifdef TEST
+#include "log.h"
+#define LEN 7001
+volatile int checksum;
+int main(){
+    int i;
+    char data[LEN];
+    av_log_level = AV_LOG_DEBUG;
+    for(i=0; i<LEN; i++)
+        data[i]= ((i*i)>>3) + 123*i;
+    for(i=0; i<1000; i++){
+        START_TIMER