[FFmpeg-devel] [PATCH] cmdutils: dont call read_header before listing devices

[Michael Niedermayer]

On Wed, Dec 17, 2014 at 10:59:37PM +0100, Lukasz Marek wrote:
> On 15.12.2014 14:18, Michael Niedermayer wrote:
> >>  cmdutils.c |    8 ++++++--
> >>  1 file changed, 6 insertions(+), 2 deletions(-)
> >>8d012a5193b0440717f89d920661913ef160e674  0001-cmdutils-dont-call-read_header-before-listing-device.patch
> >> From 332bb7456c498518ea72dfdaa0e8c3e76d383f21 Mon Sep 17 00:00:00 2001
> >>From: Lukasz Marek <lukasz.m.luki2 at gmail.com>
> >>Date: Mon, 15 Dec 2014 00:31:42 +0100
> >>Subject: [PATCH] cmdutils: dont call read_header before listing devices
> >>
> >>List device callback must be able to return valid list without opening device.
> >>This callback should return input values for open function, not vice-versa.
> >>Read header funtion is very likey to fail without proper configuration provided.
> >
> >should be ok
> 
> I changed a patch. I wanted to avoid situation where .read_close is
> called without .read_header being called before.
> 

>  cmdutils.c |   41 +++++++++++++++++++++++++++++++++++------
>  1 file changed, 35 insertions(+), 6 deletions(-)
> 9a93c401d795bae3545a6c6112e71abd98ac22ca  0001-cmdutils-dont-call-read_header-before-listing-device.patch
> From 58fe020b8f1c0e809362e152febe3ad715b1c8fc Mon Sep 17 00:00:00 2001
> From: Lukasz Marek <lukasz.m.luki2 at gmail.com>
> Date: Mon, 15 Dec 2014 00:31:42 +0100
> Subject: [PATCH] cmdutils: dont call read_header before listing devices
> 
> List device callback must be able to return valid list without opening device.
> This callback should return input values for open function, not vice-versa.
> Read header funtion is very likey to fail without proper configuration provided.
> 
> Signed-off-by: Lukasz Marek <lukasz.m.luki2 at gmail.com>
> ---
>  cmdutils.c | 41 +++++++++++++++++++++++++++++++++++------
>  1 file changed, 35 insertions(+), 6 deletions(-)
> 
> diff --git a/cmdutils.c b/cmdutils.c
> index 4e0a406..23a5f77 100644
> --- a/cmdutils.c
> +++ b/cmdutils.c
> @@ -2052,7 +2052,37 @@ void *grow_array(void *array, int elem_size, int *size, int new_size)
>  }
>  
>  #if CONFIG_AVDEVICE
> -static int print_device_sources(AVInputFormat *fmt, AVDictionary *opts)
> +static int alloc_input_context(AVFormatContext **avctx, AVInputFormat *iformat)
> +{
> +    AVFormatContext *s = avformat_alloc_context();
> +    int ret = 0;
> +
> +    *avctx = NULL;
> +    if (!s)
> +        return AVERROR(ENOMEM);
> +
> +    s->iformat = iformat;
> +    if (s->iformat->priv_data_size > 0) {
> +        s->priv_data = av_mallocz(s->iformat->priv_data_size);
> +        if (!s->priv_data) {
> +            ret = AVERROR(ENOMEM);
> +            goto error;
> +        }
> +        if (s->iformat->priv_class) {
> +            *(const AVClass**)s->priv_data= s->iformat->priv_class;
> +            av_opt_set_defaults(s->priv_data);
> +        }
> +    } else
> +        s->priv_data = NULL;
> +
> +    *avctx = s;
> +    return 0;
> +  error:
> +    avformat_free_context(s);
> +    return ret;
> +}
> +

> +static int print_device_sources(void *pfmt, AVDictionary *opts)
>  {
>      int ret, i;
>      AVFormatContext *dev = NULL;
> @@ -2069,13 +2099,12 @@ static int print_device_sources(AVInputFormat *fmt, AVDictionary *opts)
>          goto fail;
>      }
>  
> -    /* TODO: avformat_open_input calls read_header callback which is not necessary.
> -             Function like avformat_alloc_output_context2 for input could be helpful here. */
> -    av_dict_copy(&tmp_opts, opts, 0);
> -    if ((ret = avformat_open_input(&dev, NULL, fmt, &tmp_opts)) < 0) {
> +    if ((ret = alloc_input_context(&dev, fmt)) < 0) {

this fails building due to lack of a fmt variable

[...]

-- 
Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Awnsering whenever a program halts or runs forever is
On a turing machine, in general impossible (turings halting problem).
On any real computer, always possible as a real computer has a finite number
of states N, and will either halt in less than N cycles or never halt.
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