On Sat, Apr 09, 2011 at 02:47:35AM +0200, Stefano Sabatini wrote:
> From b563c12cb285f1e6eb8dc19d1a18323cd9280ea1 Mon Sep 17 00:00:00 2001
> From: Stefano Sabatini <stefano.sabatini-l...@poste.it>
> Date: Fri, 8 Apr 2011 18:32:25 +0200
> Subject: [PATCH] avio: add avio_check()
>
> The new function is more flexible than url_exist(), as it allows to
> specify which access flags to check, and does not require an explicit
> open of the checked resource.
> ---
> libavformat/avio.c | 19 +++++++++++++++++++
> libavformat/avio.h | 15 +++++++++++++++
> 2 files changed, 34 insertions(+), 0 deletions(-)
>
> diff --git a/libavformat/avio.c b/libavformat/avio.c
> index 7b066e3..cc57529 100644
> --- a/libavformat/avio.c
> +++ b/libavformat/avio.c
> @@ -362,6 +362,25 @@ int url_exist(const char *filename)
> return 1;
> }
>
> +int avio_check(const char *url, int flags)
> +{
> + URLContext *h;
> + int ret = ffurl_alloc(&h, url, flags);
> + if (ret)
> + return ret;
> +
> + if (h->prot->url_check) {
> + ret = h->prot->url_check(h, flags);
> + } else {
> + ret = ffurl_connect(h);
> + if (ret >= 0)
When is ret > 0? A quick glance at ffurl_connect suggests that it
returns 0 on success or an AVERROR < 0 on error.
> + ret = flags;
> + }
> +
> + ffurl_close(h);
> + return ret;
> +}
> +
> int64_t ffurl_size(URLContext *h)
> {
> int64_t pos, size;
> diff --git a/libavformat/avio.h b/libavformat/avio.h
> index 03b6f6f..051c06e 100644
> --- a/libavformat/avio.h
> +++ b/libavformat/avio.h
> @@ -127,6 +127,20 @@ attribute_deprecated void
> url_set_interrupt_cb(URLInterruptCB *interrupt_cb);
> int url_exist(const char *url);
>
> /**
> + * Return AVIO_* access flags corresponding to the access permissions
> + * of the resource in url, or a negative value corresponding to an
> + * AVERROR code in case of failure. The returned access flags are
> + * masked by the value in flags.
> + *
> + * @note This function is intrinsecally unsafe, in the sense that the
nit: intrins_i_cally
> + * checked resource may change its existence or permission status from
> + * one call to another. Thus you should not trust the returned value,
> + * unless you are sure that no other processes are accessing the
> + * checked resource.
> + */
> +int avio_check(const char *url, int flags);
> +
> +/**
> * The callback is called in blocking functions to test regulary if
> * asynchronous interruption is needed. AVERROR_EXIT is returned
> * in this case by the interrupted function. 'NULL' means no interrupt
> @@ -157,6 +171,7 @@ typedef struct URLProtocol {
> int priv_data_size;
> const AVClass *priv_data_class;
> int flags;
> + int (*url_check)(URLContext *h, int mask);
> } URLProtocol;
>
> #if FF_API_REGISTER_PROTOCOL
> --
> 1.7.2.3
>
> From 3337ee5fd1ca5772c293f76e7c15267077c8001f Mon Sep 17 00:00:00 2001
> From: Stefano Sabatini <stefano.sabatini-l...@poste.it>
> Date: Sat, 9 Apr 2011 01:32:37 +0200
> Subject: [PATCH] prefer avio_check() over url_exist()
>
> The problem with url_exist() is that it tries to open a resource in
> RDONLY mode. If the file is a FIFO and there is already a reading
> client, the open() call will hang.
>
> By using avio_check() with access mode of 0, the second reading
> process will check if the file exists without attempting to open it,
> thus avoiding the lock.
>
> Fix issue #1663.
> ---
> ffmpeg.c | 2 +-
> ffserver.c | 4 ++--
> libavformat/img2.c | 6 +++---
> 3 files changed, 6 insertions(+), 6 deletions(-)
>
> diff --git a/ffmpeg.c b/ffmpeg.c
> index 40e5e67..9153a5b 100644
> --- a/ffmpeg.c
> +++ b/ffmpeg.c
> @@ -3870,7 +3870,7 @@ static void opt_output_file(const char *filename)
> (strchr(filename, ':') == NULL ||
> filename[1] == ':' ||
> av_strstart(filename, "file:", NULL))) {
> - if (url_exist(filename)) {
> + if (avio_check(filename, 0) != AVERROR(ENOENT)) {
> if (!using_stdin) {
> fprintf(stderr,"File '%s' already exists. Overwrite ?
> [y/N] ", filename);
> fflush(stderr);
> diff --git a/ffserver.c b/ffserver.c
> index 6e42979..5f165dd 100644
> --- a/ffserver.c
> +++ b/ffserver.c
> @@ -3684,7 +3684,7 @@ static void build_feed_streams(void)
> for(feed = first_feed; feed != NULL; feed = feed->next_feed) {
> int fd;
>
> - if (url_exist(feed->feed_filename)) {
> + if (url_check(feed->feed_filename, URL_RDONLY)) {
Ehm...
Otherwise the patches looks good. I can confirm that it really solves
1663.
--
Anton Khirnov
signature.asc
Description: Digital signature
_______________________________________________ libav-devel mailing list libav-devel@libav.org https://lists.libav.org/mailman/listinfo/libav-devel
