Re: [FFmpeg-devel] [PATCH] Revert "avformat/file: seek back to initial position for fd protocol"

[Zhao Zhili <quinkblack@foxmail.com>]

> On May 27, 2024, at 23:22, Rémi Denis-Courmont <remi@remlab.net> wrote:
> 
> The generally expected behaviour is for software to append from the
> current position, not to keep resetting. See also how shell works:
> # (foo && bar) > file
> ...would normally concatenate the output of both commands to file.
> 
> If foo seeks like lavf, bar would instead overwrite the output of
> foo (possibly not completely).

Fine. I overlooked this use case.

> 
> This reverts commit 5c3d2177e7be7dde69a83b1b394f57976c164c84.
> ---
> libavformat/file.c | 14 +-------------
> 1 file changed, 1 insertion(+), 13 deletions(-)
> 
> diff --git a/libavformat/file.c b/libavformat/file.c
> index 0ed4cff266..3fc1e741f2 100644
> --- a/libavformat/file.c
> +++ b/libavformat/file.c
> @@ -99,7 +99,6 @@ typedef struct FileContext {
> #if HAVE_DIRENT_H
>     DIR *dir;
> #endif
> -    int64_t initial_pos;
> } FileContext;
> 
> static const AVOption file_options[] = {
> @@ -220,12 +219,7 @@ static int fd_dup(URLContext *h, int oldfd)
> static int file_close(URLContext *h)
> {
>     FileContext *c = h->priv_data;
> -    int ret;
> -
> -    if (c->initial_pos >= 0 && !h->is_streamed)
> -        lseek(c->fd, c->initial_pos, SEEK_SET);
> -
> -    ret = close(c->fd);
> +    int ret = close(c->fd);
>     return (ret == -1) ? AVERROR(errno) : 0;
> }
> 
> @@ -293,7 +287,6 @@ static int file_open(URLContext *h, const char *filename, int flags)
> 
>     av_strstart(filename, "file:", &filename);
> 
> -    c->initial_pos = -1;
>     if (flags & AVIO_FLAG_WRITE && flags & AVIO_FLAG_READ) {
>         access = O_CREAT | O_RDWR;
>         if (c->trunc)
> @@ -505,11 +498,6 @@ static int fd_open(URLContext *h, const char *filename, int flags)
>     if (c->fd == -1)
>         return AVERROR(errno);
> 
> -    if (h->is_streamed)
> -        c->initial_pos = -1;
> -    else
> -        c->initial_pos = lseek(c->fd, 0, SEEK_CUR);
> -
>     return 0;
> }
> 
> -- 
> 2.45.1
> 
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