Re: [FFmpeg-devel] [PATCH 1/5] avformat/rtsp: make use of avio_get_str() to load the sdp

[Marton Balint]

On Wed, 1 Dec 2021, lance.lmw...@gmail.com wrote:

On Wed, Dec 01, 2021 at 05:17:08PM +0200, Martin Storsjö wrote:
On Wed, 1 Dec 2021, lance.lmw...@gmail.com wrote:

> On Wed, Dec 01, 2021 at 03:55:37PM +0200, Martin Storsjö wrote:
> > On Wed, 1 Dec 2021, lance.lmw...@gmail.com wrote:
> > 
> > > From: Limin Wang <lance.lmw...@gmail.com>
> > > > Signed-off-by: Limin Wang <lance.lmw...@gmail.com>
> > > ---
> > > libavformat/rtsp.c | 30 ++++++++++++++++++++----------
> > > 1 file changed, 20 insertions(+), 10 deletions(-)
> > > > diff --git a/libavformat/rtsp.c b/libavformat/rtsp.c
> > > index e6a4993..ec8be8b 100644
> > > --- a/libavformat/rtsp.c
> > > +++ b/libavformat/rtsp.c
> > > @@ -2369,11 +2369,29 @@ static void append_source_addrs(char *buf, int 
size, const char *name,
> > >         av_strlcatf(buf, size, ",%s", addrs[i]->addr);
> > > }
> > > > +static char *read_sdp_str(AVIOContext *pb, int size)
> > > +{
> > > +    int n;
> > > +    char *str;
> > > +
> > > +    if (size < 0 || size == INT_MAX)
> > > +        return NULL;
> > > +
> > > +    str = av_malloc(size + 1);
> > > +    if (!str)
> > > +        return NULL;
> > > +    n = avio_get_str(pb, size, str, size + 1);
> > > +    if (n < size)
> > > +        avio_skip(pb, size - n);
> > 
> > What? Why do you want to skip past data in the input? Size here is just a
> > random static upper limit of how large an SDP file would be.
> yes, my fault, don't need to run avio_skip(). For avio_get_str() will return 
error only
> buflen <=0, so str is valid anyway.
> 
> > 
> > This patch totally lacks a motivation of why you want to do this.
> 
> considering the SDP is strings in file, so I think it's better to use avio_get_str().

Maybe, but warranting a patch changing things on its own, IMO.

> Also, I'm considering to remove limit of SDP_MAX_SIZE after that.

If you'd defer this patch to a patchset that does that, it might make more
sense. But I don't see much value in applying it on its own.

Yes, I consider to add new api which is avio_get_str_len() to get the string len from pb, 
before that, I want to hear no objection to use avio_get_str(). then I'll submit a patchset 
for the complete change for review.

I thought you simply want to read the file to memory. You don't need new 
API function to do that, simply use avio_read_to_bprint() with INT_MAX 
upper limit. It will allocate the necessary buffer for you, and you can 
check if ENOMEM happened with av_bprint_is_complete(), and free the buffer 
after parsing with av_bprint_finalize().

Regards,
Marton
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