avcodec/roqvideodec: Move transient GetByteContext to the stack

This avoids keeping potentially dangling pointers in the context,
beautifies the code (by replacing "&ri->gb" by gb for every access to
the GetByteContext) and also highlights the GetByteContext's short-lived
nature better.

Reviewed-by: Paul B Mahol <onemda@gmail.com>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@gmail.com>

1 files changed, 31 insertions, 30 deletions

diff --git a/libavcodec/roqvideodec.c b/libavcodec/roqvideodec.c
index dd045ed5eb..93c6e9ddf3 100644
--- a/libavcodec/roqvideodec.c
+++ b/libavcodec/roqvideodec.c
@@ -33,7 +33,7 @@
 #include "internal.h"
 #include "roqvideo.h"
 
-static void roqvideo_decode_frame(RoqContext *ri)
+static void roqvideo_decode_frame(RoqContext *ri, GetByteContext *gb)
 {
     unsigned int chunk_id = 0, chunk_arg = 0;
     unsigned long chunk_size = 0;
@@ -43,10 +43,10 @@ static void roqvideo_decode_frame(RoqContext *ri)
     roq_qcell *qcell;
     int64_t chunk_start;
 
-    while (bytestream2_get_bytes_left(&ri->gb) >= 8) {
-        chunk_id   = bytestream2_get_le16(&ri->gb);
-        chunk_size = bytestream2_get_le32(&ri->gb);
-        chunk_arg  = bytestream2_get_le16(&ri->gb);
+    while (bytestream2_get_bytes_left(gb) >= 8) {
+        chunk_id   = bytestream2_get_le16(gb);
+        chunk_size = bytestream2_get_le32(gb);
+        chunk_arg  = bytestream2_get_le16(gb);
 
         if(chunk_id == RoQ_QUAD_VQ)
             break;
@@ -56,36 +56,36 @@ static void roqvideo_decode_frame(RoqContext *ri)
             if((nv2 = chunk_arg & 0xff) == 0 && nv1 * 6 < chunk_size)
                 nv2 = 256;
             for(i = 0; i < nv1; i++) {
-                ri->cb2x2[i].y[0] = bytestream2_get_byte(&ri->gb);
-                ri->cb2x2[i].y[1] = bytestream2_get_byte(&ri->gb);
-                ri->cb2x2[i].y[2] = bytestream2_get_byte(&ri->gb);
-                ri->cb2x2[i].y[3] = bytestream2_get_byte(&ri->gb);
-                ri->cb2x2[i].u    = bytestream2_get_byte(&ri->gb);
-                ri->cb2x2[i].v    = bytestream2_get_byte(&ri->gb);
+                ri->cb2x2[i].y[0] = bytestream2_get_byte(gb);
+                ri->cb2x2[i].y[1] = bytestream2_get_byte(gb);
+                ri->cb2x2[i].y[2] = bytestream2_get_byte(gb);
+                ri->cb2x2[i].y[3] = bytestream2_get_byte(gb);
+                ri->cb2x2[i].u    = bytestream2_get_byte(gb);
+                ri->cb2x2[i].v    = bytestream2_get_byte(gb);
             }
             for(i = 0; i < nv2; i++)
                 for(j = 0; j < 4; j++)
-                    ri->cb4x4[i].idx[j] = bytestream2_get_byte(&ri->gb);
+                    ri->cb4x4[i].idx[j] = bytestream2_get_byte(gb);
         }
     }
 
-    chunk_start = bytestream2_tell(&ri->gb);
+    chunk_start = bytestream2_tell(gb);
     xpos = ypos = 0;
 
-    if (chunk_size > bytestream2_get_bytes_left(&ri->gb)) {
+    if (chunk_size > bytestream2_get_bytes_left(gb)) {
         av_log(ri->avctx, AV_LOG_ERROR, "Chunk does not fit in input buffer\n");
-        chunk_size = bytestream2_get_bytes_left(&ri->gb);
+        chunk_size = bytestream2_get_bytes_left(gb);
     }
 
-    while (bytestream2_tell(&ri->gb) < chunk_start + chunk_size) {
+    while (bytestream2_tell(gb) < chunk_start + chunk_size) {
         for (yp = ypos; yp < ypos + 16; yp += 8)
             for (xp = xpos; xp < xpos + 16; xp += 8) {
-                if (bytestream2_tell(&ri->gb) >= chunk_start + chunk_size) {
+                if (bytestream2_tell(gb) >= chunk_start + chunk_size) {
                     av_log(ri->avctx, AV_LOG_VERBOSE, "Chunk is too short\n");
                     return;
                 }
                 if (vqflg_pos < 0) {
-                    vqflg = bytestream2_get_le16(&ri->gb);
+                    vqflg = bytestream2_get_le16(gb);
                     vqflg_pos = 7;
                 }
                 vqid = (vqflg >> (vqflg_pos * 2)) & 0x3;
@@ -96,14 +96,14 @@ static void roqvideo_decode_frame(RoqContext *ri)
                 case RoQ_ID_MOT:
                     break;
                 case RoQ_ID_FCC: {
-                    int byte = bytestream2_get_byte(&ri->gb);
+                    int byte = bytestream2_get_byte(gb);
                     mx = 8 - (byte >> 4) - ((signed char) (chunk_arg >> 8));
                     my = 8 - (byte & 0xf) - ((signed char) chunk_arg);
                     ff_apply_motion_8x8(ri, xp, yp, mx, my);
                     break;
                 }
                 case RoQ_ID_SLD:
-                    qcell = ri->cb4x4 + bytestream2_get_byte(&ri->gb);
+                    qcell = ri->cb4x4 + bytestream2_get_byte(gb);
                     ff_apply_vector_4x4(ri, xp,     yp,     ri->cb2x2 + qcell->idx[0]);
                     ff_apply_vector_4x4(ri, xp + 4, yp,     ri->cb2x2 + qcell->idx[1]);
                     ff_apply_vector_4x4(ri, xp,     yp + 4, ri->cb2x2 + qcell->idx[2]);
@@ -115,12 +115,12 @@ static void roqvideo_decode_frame(RoqContext *ri)
                         if(k & 0x01) x += 4;
                         if(k & 0x02) y += 4;
 
-                        if (bytestream2_tell(&ri->gb) >= chunk_start + chunk_size) {
+                        if (bytestream2_tell(gb) >= chunk_start + chunk_size) {
                             av_log(ri->avctx, AV_LOG_VERBOSE, "Chunk is too short\n");
                             return;
                         }
                         if (vqflg_pos < 0) {
-                            vqflg = bytestream2_get_le16(&ri->gb);
+                            vqflg = bytestream2_get_le16(gb);
                             vqflg_pos = 7;
                         }
                         vqid = (vqflg >> (vqflg_pos * 2)) & 0x3;
@@ -130,24 +130,24 @@ static void roqvideo_decode_frame(RoqContext *ri)
                         case RoQ_ID_MOT:
                             break;
                         case RoQ_ID_FCC: {
-                            int byte = bytestream2_get_byte(&ri->gb);
+                            int byte = bytestream2_get_byte(gb);
                             mx = 8 - (byte >> 4) - ((signed char) (chunk_arg >> 8));
                             my = 8 - (byte & 0xf) - ((signed char) chunk_arg);
                             ff_apply_motion_4x4(ri, x, y, mx, my);
                             break;
                         }
                         case RoQ_ID_SLD:
-                            qcell = ri->cb4x4 + bytestream2_get_byte(&ri->gb);
+                            qcell = ri->cb4x4 + bytestream2_get_byte(gb);
                             ff_apply_vector_2x2(ri, x,     y,     ri->cb2x2 + qcell->idx[0]);
                             ff_apply_vector_2x2(ri, x + 2, y,     ri->cb2x2 + qcell->idx[1]);
                             ff_apply_vector_2x2(ri, x,     y + 2, ri->cb2x2 + qcell->idx[2]);
                             ff_apply_vector_2x2(ri, x + 2, y + 2, ri->cb2x2 + qcell->idx[3]);
                             break;
                         case RoQ_ID_CCC:
-                            ff_apply_vector_2x2(ri, x,     y,     ri->cb2x2 + bytestream2_get_byte(&ri->gb));
-                            ff_apply_vector_2x2(ri, x + 2, y,     ri->cb2x2 + bytestream2_get_byte(&ri->gb));
-                            ff_apply_vector_2x2(ri, x,     y + 2, ri->cb2x2 + bytestream2_get_byte(&ri->gb));
-                            ff_apply_vector_2x2(ri, x + 2, y + 2, ri->cb2x2 + bytestream2_get_byte(&ri->gb));
+                            ff_apply_vector_2x2(ri, x,     y,     ri->cb2x2 + bytestream2_get_byte(gb));
+                            ff_apply_vector_2x2(ri, x + 2, y,     ri->cb2x2 + bytestream2_get_byte(gb));
+                            ff_apply_vector_2x2(ri, x,     y + 2, ri->cb2x2 + bytestream2_get_byte(gb));
+                            ff_apply_vector_2x2(ri, x + 2, y + 2, ri->cb2x2 + bytestream2_get_byte(gb));
                             break;
                         }
                     }
@@ -201,6 +201,7 @@ static int roq_decode_frame(AVCodecContext *avctx,
     int buf_size = avpkt->size;
     RoqContext *s = avctx->priv_data;
     int copy = !s->current_frame->data[0] && s->last_frame->data[0];
+    GetByteContext gb;
     int ret;
 
     if ((ret = ff_reget_buffer(avctx, s->current_frame, 0)) < 0)
@@ -212,8 +213,8 @@ static int roq_decode_frame(AVCodecContext *avctx,
             return ret;
     }
 
-    bytestream2_init(&s->gb, buf, buf_size);
-    roqvideo_decode_frame(s);
+    bytestream2_init(&gb, buf, buf_size);
+    roqvideo_decode_frame(s, &gb);
 
     if ((ret = av_frame_ref(data, s->current_frame)) < 0)
         return ret;