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avcodec/movtextdec: Switch to pointer comparisons and bytestream API

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Improves readability and avoids a redundant index variable
that was mistakenly called "tracksize".

Reviewed-by: Philip Langdale <philipl@overt.org>
Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt 2021-12-08 17:28:29 +01:00
parent e1044e55e4
commit bbc866c9c9
1 changed files with 15 additions and 23 deletions
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36
libavcodec/movtextdec.c
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@ -102,7 +102,6 @@ typedef struct {
MovTextDefault d; MovTextDefault d;
uint8_t box_flags; uint8_t box_flags;
uint16_t style_entries, ftab_entries; uint16_t style_entries, ftab_entries;
uint64_t tracksize;
int readorder; int readorder;
int frame_width; int frame_width;
int frame_height; int frame_height;
@ -481,9 +480,7 @@ static int mov_text_decode_frame(AVCodecContext *avctx,
int ret; int ret;
AVBPrint buf; AVBPrint buf;
const char *ptr = avpkt->data, *end; const char *ptr = avpkt->data, *end;
int text_length, tsmb_type, ret_tsmb; int text_length;
uint64_t tsmb_size;
const uint8_t *tsmb;
size_t i; size_t i;
if (!ptr || avpkt->size < 2) if (!ptr || avpkt->size < 2)
@ -510,27 +507,23 @@ static int mov_text_decode_frame(AVCodecContext *avctx,
mov_text_cleanup(m); mov_text_cleanup(m);
tsmb_size = 0;
m->tracksize = 2 + text_length;
m->style_entries = 0; m->style_entries = 0;
m->box_flags = 0; m->box_flags = 0;
// Note that the spec recommends lines be no longer than 2048 characters. // Note that the spec recommends lines be no longer than 2048 characters.
av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED); av_bprint_init(&buf, 0, AV_BPRINT_SIZE_UNLIMITED);
if (text_length + 2 != avpkt->size) { if (text_length + 2 < avpkt->size) {
while (m->tracksize + 8 <= avpkt->size) { const uint8_t *tsmb = end;
int size_var; const uint8_t *const tsmb_end = avpkt->data + avpkt->size;
// A box is a minimum of 8 bytes. // A box is a minimum of 8 bytes.
tsmb = ptr + m->tracksize - 2; while (tsmb_end - tsmb >= 8) {
tsmb_size = AV_RB32(tsmb); uint64_t tsmb_size = bytestream_get_be32(&tsmb);
tsmb += 4; uint32_t tsmb_type = bytestream_get_be32(&tsmb);
tsmb_type = AV_RB32(tsmb); int size_var, ret_tsmb;
tsmb += 4;
if (tsmb_size == 1) { if (tsmb_size == 1) {
if (m->tracksize + 16 > avpkt->size) if (tsmb_end - tsmb < 8)
break; break;
tsmb_size = AV_RB64(tsmb); tsmb_size = bytestream_get_be64(&tsmb);
tsmb += 8;
size_var = 16; size_var = 16;
} else } else
size_var = 8; size_var = 8;
@ -540,13 +533,11 @@ static int mov_text_decode_frame(AVCodecContext *avctx,
av_log(avctx, AV_LOG_ERROR, "tsmb_size invalid\n"); av_log(avctx, AV_LOG_ERROR, "tsmb_size invalid\n");
return AVERROR_INVALIDDATA; return AVERROR_INVALIDDATA;
} }
if (tsmb_size > avpkt->size - m->tracksize)
break;
m->tracksize += tsmb_size;
tsmb_size -= size_var; tsmb_size -= size_var;
if (tsmb_end - tsmb < tsmb_size)
break;
for (i = 0; i < box_count; i++) { for (i = 0; i < box_count; i++) {
if (tsmb_type == box_types[i].type) { if (tsmb_type == box_types[i].type) {
if (tsmb_size < box_types[i].base_size) if (tsmb_size < box_types[i].base_size)
@ -556,6 +547,7 @@ static int mov_text_decode_frame(AVCodecContext *avctx,
break; break;
} }
} }
tsmb += tsmb_size;
} }
text_to_ass(&buf, ptr, end, avctx); text_to_ass(&buf, ptr, end, avctx);
mov_text_cleanup(m); mov_text_cleanup(m);