gst-ffmpeg: avcodec/rpza: Perform pointer advance and checks before
 using the pointers

Fixes out of array accesses
Fixes Ticket2850

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
(cherry picked from commit 3819db745da2ac7fb3faacb116788c32f4753f34)

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

Upstream-Status: Backport 

Singed-off-by: Yue Tao <yue.tao@windriver.com>

---
 libavcodec/rpza.c |    8 ++++----
 1 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/libavcodec/rpza.c b/libavcodec/rpza.c
index 635b406..f291a95 100644
--- a/gst-libs/ext/libav/libavcodec/rpza.c
+++ b/gst-libs/ext/libav/libavcodec/rpza.c
@@ -83,7 +83,7 @@ static void rpza_decode_stream(RpzaContext *s)
     unsigned short *pixels = (unsigned short *)s->frame.data[0];
 
     int row_ptr = 0;
-    int pixel_ptr = 0;
+    int pixel_ptr = -4;
     int block_ptr;
     int pixel_x, pixel_y;
     int total_blocks;
@@ -139,6 +139,7 @@ static void rpza_decode_stream(RpzaContext *s)
             colorA = AV_RB16 (&s->buf[stream_ptr]);
             stream_ptr += 2;
             while (n_blocks--) {
+                ADVANCE_BLOCK()
                 block_ptr = row_ptr + pixel_ptr;
                 for (pixel_y = 0; pixel_y < 4; pixel_y++) {
                     for (pixel_x = 0; pixel_x < 4; pixel_x++){
@@ -147,7 +148,6 @@ static void rpza_decode_stream(RpzaContext *s)
                     }
                     block_ptr += row_inc;
                 }
-                ADVANCE_BLOCK();
             }
             break;
 
@@ -184,6 +184,7 @@ static void rpza_decode_stream(RpzaContext *s)
             color4[2] |= ((21 * ta + 11 * tb) >> 5);
 
             while (n_blocks--) {
+                ADVANCE_BLOCK();
                 block_ptr = row_ptr + pixel_ptr;
                 for (pixel_y = 0; pixel_y < 4; pixel_y++) {
                     index = s->buf[stream_ptr++];
@@ -194,12 +195,12 @@ static void rpza_decode_stream(RpzaContext *s)
                     }
                     block_ptr += row_inc;
                 }
-                ADVANCE_BLOCK();
             }
             break;
 
         /* Fill block with 16 colors */
         case 0x00:
+            ADVANCE_BLOCK();
             block_ptr = row_ptr + pixel_ptr;
             for (pixel_y = 0; pixel_y < 4; pixel_y++) {
                 for (pixel_x = 0; pixel_x < 4; pixel_x++){
@@ -213,7 +214,6 @@ static void rpza_decode_stream(RpzaContext *s)
                 }
                 block_ptr += row_inc;
             }
-            ADVANCE_BLOCK();
             break;
 
         /* Unknown opcode */
-- 
1.7.5.4