ptx: emit a warning on insufficient picture data

Return the whole packet as consumed in this case and not the size the
packet should have had. Move the insufficient data check into the for
condition to fix a ISO C90 error on bigendian.

libavcodec/ptx.c

@@ -84,9 +84,7 @@ static int ptx_decode_frame(AVCodecContext *avctx, void *data, int *data_size,
     ptr    = p->data[0];
     stride = p->linesize[0];
 
-    for (y=0; y<h; y++) {
-        if (buf_end - buf < w * bytes_per_pixel)
-            break;
+    for (y = 0; y < h && buf_end - buf < w * bytes_per_pixel; y++) {
 #if HAVE_BIGENDIAN
         unsigned int x;
         for (x=0; x<w*bytes_per_pixel; x+=bytes_per_pixel)
@@ -101,6 +99,11 @@ static int ptx_decode_frame(AVCodecContext *avctx, void *data, int *data_size,
     *picture = s->picture;
     *data_size = sizeof(AVPicture);
 
+    if (y < h) {
+        av_log(avctx, AV_LOG_WARNING, "incomplete packet\n");
+        return avpkt->size;
+    }
+
     return offset + w*h*bytes_per_pixel;
 }