[FFmpeg-cvslog] 4xm: refactor decode_p_block

[Luca Barbato]

ffmpeg | branch: master | Luca Barbato <lu_zero at gentoo.org> | Sun Jun  9 21:50:57 2013 +0200| [fbd0dacc8d61ab418b3fa8e7be22017558323e56] | committer: Luca Barbato

4xm: refactor decode_p_block

Directly return from code 1, 2 and 6 codepaths and simplify the
remaining one to have a single overflow check and a single call to
mcdc.

> http://git.videolan.org/gitweb.cgi/ffmpeg.git/?a=commit;h=fbd0dacc8d61ab418b3fa8e7be22017558323e56
---

 libavcodec/4xm.c |   65 +++++++++++++++++++++++++-----------------------------
 1 file changed, 30 insertions(+), 35 deletions(-)

diff --git a/libavcodec/4xm.c b/libavcodec/4xm.c
index 2554ba9..5814c3a 100644
--- a/libavcodec/4xm.c
+++ b/libavcodec/4xm.c
@@ -342,52 +342,26 @@ static int decode_p_block(FourXContext *f, uint16_t *dst, uint16_t *src,
     uint16_t *start = (uint16_t *)f->last_picture->data[0];
     uint16_t *end   = start + stride * (f->avctx->height - h + 1) - (1 << log2w);
     int ret;
+    int scale   = 1;
+    unsigned dc = 0;
 
     if (code < 0 || code > 6 || log2w < 0)
         return AVERROR_INVALIDDATA;
 
-    if (code == 0) {
-        src += f->mv[bytestream2_get_byte(&f->g)];
-        if (start > src || src > end) {
-            av_log(f->avctx, AV_LOG_ERROR, "mv out of pic\n");
-            return AVERROR_INVALIDDATA;
-        }
-        mcdc(dst, src, log2w, h, stride, 1, 0);
-    } else if (code == 1) {
+    if (code == 1) {
         log2h--;
         if ((ret = decode_p_block(f, dst, src, log2w, log2h, stride)) < 0)
             return ret;
-        if ((ret = decode_p_block(f, dst + (stride << log2h),
-                                  src + (stride << log2h),
-                                  log2w, log2h, stride)) < 0)
-            return ret;
+        return decode_p_block(f, dst + (stride << log2h),
+                              src + (stride << log2h),
+                              log2w, log2h, stride);
     } else if (code == 2) {
         log2w--;
         if ((ret = decode_p_block(f, dst , src, log2w, log2h, stride)) < 0)
             return ret;
-        if ((ret = decode_p_block(f, dst + (1 << log2w),
-                                  src + (1 << log2w),
-                                  log2w, log2h, stride)) < 0)
-            return ret;
-    } else if (code == 3 && f->version < 2) {
-        if (start > src || src > end) {
-            av_log(f->avctx, AV_LOG_ERROR, "mv out of pic\n");
-            return AVERROR_INVALIDDATA;
-        }
-        mcdc(dst, src, log2w, h, stride, 1, 0);
-    } else if (code == 4) {
-        src += f->mv[bytestream2_get_byte(&f->g)];
-        if (start > src || src > end) {
-            av_log(f->avctx, AV_LOG_ERROR, "mv out of pic\n");
-            return AVERROR_INVALIDDATA;
-        }
-        mcdc(dst, src, log2w, h, stride, 1, bytestream2_get_le16(&f->g2));
-    } else if (code == 5) {
-        if (start > src || src > end) {
-            av_log(f->avctx, AV_LOG_ERROR, "mv out of pic\n");
-            return AVERROR_INVALIDDATA;
-        }
-        mcdc(dst, src, log2w, h, stride, 0, bytestream2_get_le16(&f->g2));
+        return decode_p_block(f, dst + (1 << log2w),
+                              src + (1 << log2w),
+                              log2w, log2h, stride);
     } else if (code == 6) {
         if (log2w) {
             dst[0]      = bytestream2_get_le16(&f->g2);
@@ -396,7 +370,28 @@ static int decode_p_block(FourXContext *f, uint16_t *dst, uint16_t *src,
             dst[0]      = bytestream2_get_le16(&f->g2);
             dst[stride] = bytestream2_get_le16(&f->g2);
         }
+        return 0;
+    }
+
+    if (code == 0) {
+        src  += f->mv[bytestream2_get_byte(&f->g)];
+    } else if (code == 3 && f->version >= 2) {
+        return 0;
+    } else if (code == 4) {
+        src  += f->mv[bytestream2_get_byte(&f->g)];
+        dc    = bytestream2_get_le16(&f->g2);
+    } else if (code == 5) {
+        scale = 0;
+        dc    = bytestream2_get_le16(&f->g2);
     }
+
+    if (start > src || src > end) {
+        av_log(f->avctx, AV_LOG_ERROR, "mv out of pic\n");
+        return AVERROR_INVALIDDATA;
+    }
+
+    mcdc(dst, src, log2w, h, stride, scale, dc);
+
     return 0;
 }