imgutils: introduce internal image_get_linesize() and use it

Allow to factorize code between av_image_get_linesize() and
av_image_fill_linesizes(), and add missing checks.

Increase robustness.

libavutil/imgutils.c

@@ -43,27 +43,41 @@ void av_image_fill_max_pixsteps(int max_pixsteps[4], int max_pixstep_comps[4],
     }
 }
 
+static inline
+int image_get_linesize(int width, int plane,
+                       int max_step, int max_step_comp,
+                       const AVPixFmtDescriptor *desc)
+{
+    int s, shifted_w, linesize;
+
+    if (width < 0)
+        return AVERROR(EINVAL);
+    s = (max_step_comp == 1 || max_step_comp == 2) ? desc->log2_chroma_w : 0;
+    shifted_w = ((width + (1 << s) - 1)) >> s;
+    if (shifted_w && max_step > INT_MAX / shifted_w)
+        return AVERROR(EINVAL);
+    linesize = max_step * shifted_w;
+    if (desc->flags & PIX_FMT_BITSTREAM)
+        linesize = (linesize + 7) >> 3;
+    return linesize;
+}
+
 int av_image_get_linesize(enum PixelFormat pix_fmt, int width, int plane)
 {
     const AVPixFmtDescriptor *desc = &av_pix_fmt_descriptors[pix_fmt];
     int max_step     [4];       /* max pixel step for each plane */
     int max_step_comp[4];       /* the component for each plane which has the max pixel step */
-    int s, linesize;
 
     if ((unsigned)pix_fmt >= PIX_FMT_NB || desc->flags & PIX_FMT_HWACCEL)
         return AVERROR(EINVAL);
 
     av_image_fill_max_pixsteps(max_step, max_step_comp, desc);
-    s = (max_step_comp[plane] == 1 || max_step_comp[plane] == 2) ? desc->log2_chroma_w : 0;
-    linesize = max_step[plane] * (((width + (1 << s) - 1)) >> s);
-    if (desc->flags & PIX_FMT_BITSTREAM)
-        linesize = (linesize + 7) >> 3;
-    return linesize;
+    return image_get_linesize(width, plane, max_step[plane], max_step_comp[plane], desc);
 }
 
 int av_image_fill_linesizes(int linesizes[4], enum PixelFormat pix_fmt, int width)
 {
-    int i;
+    int i, ret;
     const AVPixFmtDescriptor *desc = &av_pix_fmt_descriptors[pix_fmt];
     int max_step     [4];       /* max pixel step for each plane */
     int max_step_comp[4];       /* the component for each plane which has the max pixel step */
@@ -75,13 +89,9 @@ int av_image_fill_linesizes(int linesizes[4], enum PixelFormat pix_fmt, int widt
 
     av_image_fill_max_pixsteps(max_step, max_step_comp, desc);
     for (i = 0; i < 4; i++) {
-        int s = (max_step_comp[i] == 1 || max_step_comp[i] == 2) ? desc->log2_chroma_w : 0;
-        int shifted_w = ((width + (1 << s) - 1)) >> s;
-        if (max_step[i] > INT_MAX / shifted_w)
-            return AVERROR(EINVAL);
-        linesizes[i] = max_step[i] * shifted_w;
-        if (desc->flags & PIX_FMT_BITSTREAM)
-            linesizes[i] = (linesizes[i] + 7) >> 3;
+        if ((ret = image_get_linesize(width, i, max_step[i], max_step_comp[i], desc)) < 0)
+            return ret;
+        linesizes[i] = ret;
     }
 
     return 0;