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Code Issues Releases Activity

avformat/avio: clarify that AVSEEK_FORCE has no effect

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avio_seek() never supported SEEK_END and returned AVERROR(EINVAL) when
specified, so the later check "(whence != SEEK_END || force)" was always true.

This also means that AVSEEK_FORCE had no effect since 7a6fe01f99, that is 15
years ago. Rather than changing behaviour, let's document instead that the flag
has no effect.

Also fixed other commit 41ed7ab45f which confused ORing / passing AVSEEK_FORCE
and AVSEEK_SIZE in the docs.

Signed-off-by: Valerii Zapodovnikov <val.zapod.vz@gmail.com>
This commit is contained in:
Valerii Zapodovnikov
2025-08-04 23:53:49 +03:00
committed by Marton Balint
parent 134fbfd1dc
commit 8426622bb9
2 changed files with 6 additions and 8 deletions
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6
libavformat/avio.h
View File

@@ -461,17 +461,17 @@ int avio_put_str16be(AVIOContext *s, const char *str);
void avio_write_marker(AVIOContext *s, int64_t time, enum AVIODataMarkerType type); void avio_write_marker(AVIOContext *s, int64_t time, enum AVIODataMarkerType type);
/** /**
* ORing this as the "whence" parameter to a seek function causes it to * Passing this as the "whence" parameter to a seek function causes it to
* return the filesize without seeking anywhere. Supporting this is optional. * return the filesize without seeking anywhere. Supporting this is optional.
* If it is not supported then the seek function will return <0. * If it is not supported then the seek function will return <0.
*/ */
#define AVSEEK_SIZE 0x10000 #define AVSEEK_SIZE 0x10000
/** /**
* Passing this flag as the "whence" parameter to a seek function causes it to * OR'ing this flag into the "whence" parameter to a seek function causes it to
* seek by any means (like reopening and linear reading) or other normally unreasonable * seek by any means (like reopening and linear reading) or other normally unreasonable
* means that can be extremely slow. * means that can be extremely slow.
* This may be ignored by the seek code. * This is the default and therefore ignored by the seek code since 2010.
*/ */
#define AVSEEK_FORCE 0x20000 #define AVSEEK_FORCE 0x20000

8
libavformat/aviobuf.c
View File

@@ -238,10 +238,9 @@ int64_t avio_seek(AVIOContext *s, int64_t offset, int whence)
FFIOContext *const ctx = ffiocontext(s); FFIOContext *const ctx = ffiocontext(s);
int64_t offset1; int64_t offset1;
int64_t pos; int64_t pos;
int force = whence & AVSEEK_FORCE;
int buffer_size; int buffer_size;
int short_seek; int short_seek;
whence &= ~AVSEEK_FORCE; whence &= ~AVSEEK_FORCE; // force flag does nothing
if(!s) if(!s)
return AVERROR(EINVAL); return AVERROR(EINVAL);
@@ -282,8 +281,7 @@ int64_t avio_seek(AVIOContext *s, int64_t offset, int whence)
} else if ((!(s->seekable & AVIO_SEEKABLE_NORMAL) || } else if ((!(s->seekable & AVIO_SEEKABLE_NORMAL) ||
offset1 <= buffer_size + short_seek) && offset1 <= buffer_size + short_seek) &&
!s->write_flag && offset1 >= 0 && !s->write_flag && offset1 >= 0 &&
(!s->direct || !s->seek) && (!s->direct || !s->seek)) {
(whence != SEEK_END || force)) {
while(s->pos < offset && !s->eof_reached) while(s->pos < offset && !s->eof_reached)
fill_buffer(s); fill_buffer(s);
if (s->eof_reached) if (s->eof_reached)
@@ -300,7 +298,7 @@ int64_t avio_seek(AVIOContext *s, int64_t offset, int whence)
s->pos = pos; s->pos = pos;
s->eof_reached = 0; s->eof_reached = 0;
fill_buffer(s); fill_buffer(s);
return avio_seek(s, offset, SEEK_SET | force); return avio_seek(s, offset, SEEK_SET);
} else { } else {
int64_t res; int64_t res;
if (s->write_flag) { if (s->write_flag) {