[PATCH] Simplify decode_format80 function

[Adam Iglewski]

---
 libavcodec/vqavideo.c |  121 ++++++++++++++++---------------------------------
 1 files changed, 40 insertions(+), 81 deletions(-)

diff --git a/libavcodec/vqavideo.c b/libavcodec/vqavideo.c
index 67dd7de..9646d67 100644
--- a/libavcodec/vqavideo.c
+++ b/libavcodec/vqavideo.c
@@ -199,101 +199,61 @@ static av_cold int vqa_decode_init(AVCodecContext *avctx)
     return 0;
 }
 
-#define CHECK_COUNT() \
-    if (dest_index + count > dest_size) { \
-        av_log(NULL, AV_LOG_ERROR, "  VQA video: decode_format80 problem: next op would overflow dest_index\n"); \
-        av_log(NULL, AV_LOG_ERROR, "  VQA video: current dest_index = %d, count = %d, dest_size = %d\n", \
-            dest_index, count, dest_size); \
+#define CHECK_PTR() \
+    if (dest + count > dest_end) { \
+        av_log(NULL, AV_LOG_ERROR, "  VQA video: decode_format80 problem: next op would overflow dest buffer\n"); \
         return; \
     }
 
 static void decode_format80(const unsigned char *src, int src_size,
     unsigned char *dest, int dest_size, int check_size) {
 
-    int src_index = 0;
-    int dest_index = 0;
+    const unsigned char *from,*src_end = src+src_size;
+    unsigned char *dest_end = dest+dest_size;
     int count;
     int src_pos;
-    unsigned char color;
-    int i;
+    unsigned char code;
     int new_format = !*src || src_size > 0xffff;
 
     if (new_format)
-        src_index++;
+        src++;
 
-    while (src_index < src_size) {
+    while (src < src_end) {
 
-        vqa_debug("      opcode %02X: ", src[src_index]);
+        code = *src++;
 
         /* 0x80 means that frame is finished */
-        if (src[src_index] == 0x80)
+        if (code == 0x80)
             return;
 
-        if (dest_index >= dest_size) {
-            av_log(NULL, AV_LOG_ERROR, "  VQA video: decode_format80 problem: dest_index (%d) exceeded dest_size (%d)\n",
-                dest_index, dest_size);
-            return;
-        }
-
-        if (src[src_index] == 0xFF) {
-
-            src_index++;
-            count = AV_RL16(&src[src_index]);
-            src_index += 2;
-            src_pos = AV_RL16(&src[src_index]);
-            if(new_format)
-                src_pos = dest_index-src_pos;
-            src_index += 2;
-            vqa_debug("(1) copy %X bytes from absolute pos %X\n", count, src_pos);
-            CHECK_COUNT();
-            for (i = 0; i < count; i++)
-                dest[dest_index + i] = dest[src_pos + i];
-            dest_index += count;
-
-        } else if (src[src_index] == 0xFE) {
-
-            src_index++;
-            count = AV_RL16(&src[src_index]);
-            src_index += 2;
-            color = src[src_index++];
-            vqa_debug("(2) set %X bytes to %02X\n", count, color);
-            CHECK_COUNT();
-            memset(&dest[dest_index], color, count);
-            dest_index += count;
-
-        } else if ((src[src_index] & 0xC0) == 0xC0) {
-
-            count = (src[src_index++] & 0x3F) + 3;
-            src_pos = AV_RL16(&src[src_index]);
-            if(new_format)
-                src_pos = dest_index-src_pos;
-            src_index += 2;
-            vqa_debug("(3) copy %X bytes from absolute pos %X\n", count, src_pos);
-            CHECK_COUNT();
-            for (i = 0; i < count; i++)
-                dest[dest_index + i] = dest[src_pos + i];
-            dest_index += count;
-
-        } else if (src[src_index] > 0x80) {
-
-            count = src[src_index++] & 0x3F;
-            vqa_debug("(4) copy %X bytes from source to dest\n", count);
-            CHECK_COUNT();
-            memcpy(&dest[dest_index], &src[src_index], count);
-            src_index += count;
-            dest_index += count;
-
-        } else {
-
-            count = ((src[src_index] & 0x70) >> 4) + 3;
-            src_pos = AV_RB16(&src[src_index]) & 0x0FFF;
-            src_index += 2;
-            vqa_debug("(5) copy %X bytes from relpos %X\n", count, src_pos);
-            CHECK_COUNT();
-            for (i = 0; i < count; i++)
-                dest[dest_index + i] = dest[dest_index - src_pos + i];
-            dest_index += count;
-        }
+            if(code == 0xFE) {
+                count = bytestream_get_le16(&src);
+                CHECK_PTR()
+                memset(dest, *src++, count);
+                dest += count;
+                continue;
+            } else if((code == 0xFF) || ((code & 0xC0) == 0xC0)) {
+                if(code == 0xFF)
+                    count = bytestream_get_le16(&src);
+                else
+                    count = (code & 0x3F) + 3;
+                src_pos = bytestream_get_le16(&src);
+                if(new_format)
+                    from = dest-src_pos;
+                else
+                    from = dest_end-dest_size+src_pos;
+            } else if (code > 0x80) {
+                count = (code & 0x3F);
+                from = src;
+                src += count;
+            } else {
+                count = ((code & 0x70) >> 4) + 3;
+                src_pos = ((code & 0x0F) << 8) | *src++;
+                from = dest-src_pos;
+            }
+            CHECK_PTR()
+            while(count--)
+                *dest++ = *from++;
     }
 
     /* validate that the entire destination buffer was filled; this is
@@ -301,9 +261,8 @@ static void decode_format80(const unsigned char *src, int src_size,
      * codebook entry; it is not important for compressed codebooks because
      * not every entry needs to be filled */
     if (check_size)
-        if (dest_index < dest_size)
-            av_log(NULL, AV_LOG_ERROR, "  VQA video: decode_format80 problem: decode finished with dest_index (%d) < dest_size (%d)\n",
-                dest_index, dest_size);
+        if (dest < dest_end)
+            av_log(NULL, AV_LOG_ERROR, "  VQA video: decode_format80 problem: decode finished with dest < dest_end\n");
 }
 
 static inline void vqa_copy_hc_block(uint16_t *pixels,int stride,const uint16_t *codebook,
-- 
1.6.0.4



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