X-Git-Url: https://git.sesse.net/?a=blobdiff_plain;f=libavutil%2Fadler32.c;h=4f2001025b372ad7c33c2cab76569e18c3b4b3f2;hb=28734ac995ef4ea9be2203144362a585b2296637;hp=1d814b4561616bcb66ccec412df108a45b704e11;hpb=38603ff65d956c6af61021662cfc76d6e54d1d34;p=ffmpeg

diff --git a/libavutil/adler32.c b/libavutil/adler32.c
index 1d814b45616..4f2001025b3 100644
--- a/libavutil/adler32.c
+++ b/libavutil/adler32.c
@@ -1,43 +1,73 @@
-/* adler32.c -- compute the Adler-32 checksum of a data stream
+/*
+ * Compute the Adler-32 checksum of a data stream.
+ * This is a modified version based on adler32.c from the zlib library.
+ *
  * Copyright (C) 1995 Mark Adler
- * For conditions of distribution and use, see copyright notice in zlib.h
+ *
+ * This software is provided 'as-is', without any express or implied
+ * warranty.  In no event will the authors be held liable for any damages
+ * arising from the use of this software.
+ *
+ * Permission is granted to anyone to use this software for any purpose,
+ * including commercial applications, and to alter it and redistribute it
+ * freely, subject to the following restrictions:
+ *
+ * 1. The origin of this software must not be misrepresented; you must not
+ *    claim that you wrote the original software. If you use this software
+ *    in a product, an acknowledgment in the product documentation would be
+ *    appreciated but is not required.
+ * 2. Altered source versions must be plainly marked as such, and must not be
+ *    misrepresented as being the original software.
+ * 3. This notice may not be removed or altered from any source distribution.
  */
 
-#include "common.h"
+#include "config.h"
 #include "adler32.h"
 
 #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 DO2(buf)  DO1(buf); DO1(buf);
-#define DO4(buf)  DO2(buf); DO2(buf);
-#define DO8(buf)  DO4(buf); DO4(buf);
-#define DO16(buf) DO8(buf); DO8(buf);
+#define DO4(buf)  DO1(buf); DO1(buf); DO1(buf); DO1(buf);
+#define DO16(buf) DO4(buf); DO4(buf); DO4(buf); DO4(buf);
 
 unsigned long av_adler32_update(unsigned long adler, const uint8_t *buf, unsigned int len)
 {
     unsigned long s1 = adler & 0xffff;
-    unsigned long s2 = (adler >> 16) & 0xffff;
-    int k;
+    unsigned long s2 = adler >> 16;
 
-    if (buf == NULL) return 1L;
-
-    while (len > 0) {
-        k = FFMIN(len, NMAX);
-        len -= k;
-#ifndef CONFIG_SMALL
-        while (k >= 16) {
-            DO16(buf);
-            k -= 16;
-        }
+    while (len>0) {
+#if 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"
+#include "timer.h"
+#define LEN 7001
+volatile int checksum;
+int main(void){
+    int i;
+    char data[LEN];
+    av_log_set_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
+        checksum= av_adler32_update(1, data, LEN);
+        STOP_TIMER("adler")
+    }
+    av_log(NULL, AV_LOG_DEBUG, "%X == 50E6E508\n", checksum);
+    return 0;
+}
+#endif