[FFmpeg-devel] [PATCH] avformat/cache - delete cache file after closing handle

[Nicolas George]

Gyan (12019-05-22):
> 
> The existing practice of unlinking path immediately after acquiring file
> handle was returning (unchecked) EPERM error on Windows. Switched to
> deletion after closing handle.
> Confirmed that cache protocol temp files are deleted in Windows 7 when
> ffmpeg exits.
> 
> The cache protocol calls avutil/avpriv_tempfile(), which in turn, calls
> mkstemp (for me), so I don't see the provision to append O_TEMPORARY as a
> flag while opening. mkstemp only applies
> _O_RDWR | _O_CREAT | _O_EXCL | _O_BINARY
> 
> Should be tested in other environments. If it works, supersedes
> https://patchwork.ffmpeg.org/patch/13242/
> 
> Thanks,
> Gyan

> From f1f17020dd96205a60195e310d8c3b53126c2e00 Mon Sep 17 00:00:00 2001
> From: Gyan Doshi <ffmpeg at gyani.pro>
> Date: Wed, 22 May 2019 18:05:04 +0530
> Subject: [PATCH] avformat/cache - delete cache file after closing handle
> 
> Ensures cache file deletion on Windows, when compiled under MinGW.
> ---
>  libavformat/cache.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/libavformat/cache.c b/libavformat/cache.c
> index 66bbbf54c9..1db13ceefc 100644
> --- a/libavformat/cache.c
> +++ b/libavformat/cache.c
> @@ -54,6 +54,7 @@ typedef struct CacheEntry {
>  typedef struct Context {
>      AVClass *class;
>      int fd;
> +    char *filename;
>      struct AVTreeNode *root;
>      int64_t logical_pos;
>      int64_t cache_pos;
> @@ -83,7 +84,7 @@ static int cache_open(URLContext *h, const char *arg, int flags, AVDictionary **
>          return c->fd;
>      }
>  

> -    unlink(buffername);

On systems that allow deleting the file when it is still in use deleting
it immediately is a better idea: it reduces the risk of leaving it if
the application is interrupted prematurely.

> +    c->filename = av_strdup(buffername);

Missing error check.

>      av_freep(&buffername);
>  
>      return ffurl_open_whitelist(&c->inner, arg, flags, &h->interrupt_callback,
> @@ -292,11 +293,15 @@ static int enu_free(void *opaque, void *elem)
>  static int cache_close(URLContext *h)
>  {
>      Context *c= h->priv_data;
> +    int ret;
>  
>      av_log(h, AV_LOG_INFO, "Statistics, cache hits:%"PRId64" cache misses:%"PRId64"\n",
>             c->cache_hit, c->cache_miss);
>  
>      close(c->fd);
> +    ret = avpriv_io_delete(c->filename);
> +    if (ret < 0)
> +        av_log(h, AV_LOG_ERROR, "Could not delete %s. Error is %s\n", c->filename, av_err2str(ret));
>      ffurl_close(c->inner);
>      av_tree_enumerate(c->root, NULL, NULL, enu_free);
>      av_tree_destroy(c->root);

Regards,

-- 
  Nicolas George
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