Re: [FFmpeg-devel] [PATCH 01/10] avformat/segment: Add segment_write_temp option

[Marton Balint <cus@passwd.hu>]

On Fri, 13 Jun 2025, softworkz wrote:

> From: softworkz <softworkz@hotmail.com>
>
> Allows to write segments as temp files (.tmp) which
> are renamed on completion.
>
> Signed-off-by: softworkz <softworkz@hotmail.com>
> ---
> libavformat/segment.c | 30 +++++++++++++++++++++++++++---
> 1 file changed, 27 insertions(+), 3 deletions(-)
>
> diff --git a/libavformat/segment.c b/libavformat/segment.c
> index 65323ec678..04e973a198 100644
> --- a/libavformat/segment.c
> +++ b/libavformat/segment.c
> @@ -121,6 +121,7 @@ typedef struct SegmentContext {
>     int   break_non_keyframes;
>     int   write_empty;
>
> +    int segment_write_temp; ///< write segments as temp files and rename on completion
>     int use_rename;
>     char temp_list_filename[1024];
>
> @@ -226,6 +227,15 @@ static int set_segment_filename(AVFormatContext *s)
>              seg->entry_prefix ? seg->entry_prefix : "",
>              av_basename(oc->url));
>
> +    // Write segment as a temp file and rename on completion
> +    if(seg->segment_write_temp) {
> +        av_strlcatf(buf, sizeof(buf), ".tmp");
> +        char *temp_name = av_strdup(buf);
> +        if (!temp_name)
> +            return AVERROR(ENOMEM);

You should use av_asprintf() directly instead of strlcatf() + av_strdup()

> +        ff_format_set_url(oc, temp_name);
> +    }
> +
>     return 0;
> }
>
> @@ -372,7 +382,7 @@ static int segment_end(AVFormatContext *s, int write_trailer, int is_last)
>             SegmentListEntry *entry = av_mallocz(sizeof(*entry));
>             if (!entry) {
>                 ret = AVERROR(ENOMEM);
> -                goto end;
> +                goto fail;
>             }
>
>             /* append new element */
> @@ -393,7 +403,7 @@ static int segment_end(AVFormatContext *s, int write_trailer, int is_last)
>             }
>
>             if ((ret = segment_list_open(s)) < 0)
> -                goto end;
> +                goto fail;
>             for (entry = seg->segment_list_entries; entry; entry = entry->next)
>                 segment_list_print_entry(seg->list_pb, seg->list_type, entry, s);
>             if (seg->list_type == LIST_TYPE_M3U8 && is_last)
> @@ -450,7 +460,20 @@ static int segment_end(AVFormatContext *s, int write_trailer, int is_last)
>         }
>     }
>
> -end:
> +    ff_format_io_close(oc, &oc->pb);
> +
> +    // Now rename the .tmp file to its actual name.
> +    if (seg->segment_write_temp) {
> +        char *final_filename = av_strndup(oc->url, strlen(oc->url) - 4);
> +        if (!final_filename)
> +            return AVERROR(ENOMEM);

goto fail?

> +        ret = ff_rename(oc->url, final_filename, s);
> +        av_free(final_filename);
> +    }
> +
> +    return ret;
> +
> +fail:
>     ff_format_io_close(oc, &oc->pb);
>
>     return ret;
> @@ -1075,6 +1098,7 @@ static const AVOption options[] = {
>     { "reset_timestamps", "reset timestamps at the beginning of each segment", OFFSET(reset_timestamps), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, E },
>     { "initial_offset", "set initial timestamp offset", OFFSET(initial_offset), AV_OPT_TYPE_DURATION, {.i64 = 0}, -INT64_MAX, INT64_MAX, E },
>     { "write_empty_segments", "allow writing empty 'filler' segments", OFFSET(write_empty), AV_OPT_TYPE_BOOL, {.i64 = 0}, 0, 1, E },
> +    { "segment_write_temp", "write segments as temp files (.tmp) and rename on completion", OFFSET(segment_write_temp), AV_OPT_TYPE_BOOL,   {.i64 = 0}, 0, 1, E },
>     { NULL },
> };

Regards,
Marton
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