diff ffmpeg/libavutil/adler32.c @ 11:f445c3017523

new files

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/ffmpeg/libavutil/adler32.c	Sun Apr 21 11:16:23 2013 +0200
@@ -0,0 +1,123 @@
+/*
+ * 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
+ *
+ * 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 "config.h"
+#include "adler32.h"
+#include "common.h"
+#include "intreadwrite.h"
+
+#define BASE 65521L /* largest prime smaller than 65536 */
+
+#define DO1(buf)  { s1 += *buf++; s2 += s1; }
+#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;
+
+    while (len > 0) {
+#if HAVE_FAST_64BIT && HAVE_FAST_UNALIGNED && !CONFIG_SMALL
+        unsigned len2 = FFMIN((len-1) & ~7, 23*8);
+        if (len2) {
+            uint64_t a1= 0;
+            uint64_t a2= 0;
+            uint64_t b1= 0;
+            uint64_t b2= 0;
+            len -= len2;
+            s2 += s1*len2;
+            while (len2 >= 8) {
+                uint64_t v = AV_RN64(buf);
+                a2 += a1;
+                b2 += b1;
+                a1 +=  v    &0x00FF00FF00FF00FF;
+                b1 += (v>>8)&0x00FF00FF00FF00FF;
+                len2 -= 8;
+                buf+=8;
+            }
+
+            //We combine the 8 interleaved adler32 checksums without overflows
+            //Decreasing the number of iterations would allow below code to be
+            //simplified but would likely be slower due to the fewer iterations
+            //of the inner loop
+            s1 += ((a1+b1)*0x1000100010001)>>48;
+            s2 += ((((a2&0xFFFF0000FFFF)+(b2&0xFFFF0000FFFF)+((a2>>16)&0xFFFF0000FFFF)+((b2>>16)&0xFFFF0000FFFF))*0x800000008)>>32)
+#if HAVE_BIGENDIAN
+                 + 2*((b1*0x1000200030004)>>48)
+                 +   ((a1*0x1000100010001)>>48)
+                 + 2*((a1*0x0000100020003)>>48);
+#else
+                 + 2*((a1*0x4000300020001)>>48)
+                 +   ((b1*0x1000100010001)>>48)
+                 + 2*((b1*0x3000200010000)>>48);
+#endif
+        }
+#else
+        while (len > 4  && s2 < (1U << 31)) {
+            DO4(buf);
+            len -= 4;
+        }
+#endif
+        DO1(buf); len--;
+        s1 %= BASE;
+        s2 %= BASE;
+    }
+    return (s2 << 16) | s1;
+}
+
+#ifdef TEST
+// LCOV_EXCL_START
+#include <string.h>
+#include "log.h"
+#include "timer.h"
+#define LEN 7001
+
+static volatile int checksum;
+
+int main(int argc, char **argv)
+{
+    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;
+
+    if (argc > 1 && !strcmp(argv[1], "-t")) {
+        for (i = 0; i < 1000; i++) {
+            START_TIMER;
+            checksum = av_adler32_update(1, data, LEN);
+            STOP_TIMER("adler");
+        }
+    } else {
+        checksum = av_adler32_update(1, data, LEN);
+    }
+
+    av_log(NULL, AV_LOG_DEBUG, "%X (expected 50E6E508)\n", checksum);
+    return checksum == 0x50e6e508 ? 0 : 1;
+}
+// LCOV_EXCL_STOP
+#endif