[FFmpeg-devel] [PATCH 1/2] avcodec/roqvideodec: Move transient GetByteContext to the stack
Paul B Mahol
onemda at gmail.com
Sun Aug 30 22:28:50 EEST 2020
On 8/30/20, Andreas Rheinhardt <andreas.rheinhardt at gmail.com> wrote:
> 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.
>
> Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt at gmail.com>
> ---
> libavcodec/roqvideo.h | 1 -
> libavcodec/roqvideodec.c | 61 ++++++++++++++++++++--------------------
> 2 files changed, 31 insertions(+), 31 deletions(-)
>
Probably ok.
> diff --git a/libavcodec/roqvideo.h b/libavcodec/roqvideo.h
> index 3da6eaa991..f47b2c8e6f 100644
> --- a/libavcodec/roqvideo.h
> +++ b/libavcodec/roqvideo.h
> @@ -52,7 +52,6 @@ typedef struct RoqContext {
> roq_cell cb2x2[256];
> roq_qcell cb4x4[256];
>
> - GetByteContext gb;
> int width, height;
>
> /* Encoder only data */
> 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;
> --
> 2.20.1
>
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