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avcodec/srtenc: Don't copy data around unnecessarily

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Using av_bprint_init_for_buffer() avoids copying data
into the internal AVBPrint buffer (or worse: to allocate
a temporary buffer in case the internal buffer does not
suffice). It also ensures that the data is always
0-terminated, whereas the current code never does this
and returns success in case the length of the
string to write and the size of the buffer coincide.

Signed-off-by: Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
This commit is contained in:
Andreas Rheinhardt 2024-02-18 00:27:14 +01:00
parent b8a00a1f73
commit 686af4578c
1 changed files with 2 additions and 8 deletions
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10
libavcodec/srtenc.c
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@ -23,7 +23,6 @@
#include <stdarg.h>
#include "avcodec.h"
#include "libavutil/avstring.h"
#include "libavutil/bprint.h"
#include "ass_split.h"
#include "ass.h"
@ -138,7 +137,6 @@ static av_cold int srt_encode_init(AVCodecContext *avctx)
SRTContext *s = avctx->priv_data;
s->avctx = avctx;
s->ass_ctx = ff_ass_split(avctx->subtitle_header);
av_bprint_init(&s->buffer, 0, AV_BPRINT_SIZE_UNLIMITED);
return s->ass_ctx ? 0 : AVERROR_INVALIDDATA;
}
@ -237,7 +235,7 @@ static int encode_frame(AVCodecContext *avctx,
ASSDialog *dialog;
int i;
av_bprint_clear(&s->buffer);
av_bprint_init_for_buffer(&s->buffer, buf, bufsize);
for (i=0; i<sub->num_rects; i++) {
const char *ass = sub->rects[i]->ass;
@ -257,16 +255,13 @@ static int encode_frame(AVCodecContext *avctx,
ff_ass_free_dialog(&dialog);
}
if (!av_bprint_is_complete(&s->buffer))
return AVERROR(ENOMEM);
if (!s->buffer.len)
return 0;
if (s->buffer.len > bufsize) {
if (!av_bprint_is_complete(&s->buffer)) {
av_log(avctx, AV_LOG_ERROR, "Buffer too small for ASS event.\n");
return AVERROR_BUFFER_TOO_SMALL;
}
memcpy(buf, s->buffer.str, s->buffer.len);
return s->buffer.len;
}
@ -287,7 +282,6 @@ static int srt_encode_close(AVCodecContext *avctx)
{
SRTContext *s = avctx->priv_data;
ff_ass_split_free(s->ass_ctx);
av_bprint_finalize(&s->buffer, NULL);
return 0;
}