[FFmpeg-devel] [PATCH] lavf: add zip protocol

[wm4]

On Sun, 29 Mar 2015 01:12:32 +0200
Ivan Kalvachev <ikalvachev at gmail.com> wrote:

> On 3/28/15, Peter Ross <pross at xvid.org> wrote:
> > On Sat, Mar 28, 2015 at 10:24:55PM +0100, wm4 wrote:
> >> On Sun, 29 Mar 2015 08:10:29 +1100
> >> Peter Ross <pross at xvid.org> wrote:
> >>
> >> > On Sat, Mar 28, 2015 at 08:38:40PM +0100, Lukasz Marek wrote:
> >> > > On 28.03.2015 20:13, Nicolas George wrote:
> >> > > >L'octidi 8 germinal, an CCXXIII, Lukasz Marek a écrit :
> >> > > >>I will try to use this libarchive first and do some tests. Your
> >> > > >> approach may
> >> > > >>collapse in case compression libraries doesn't support parallel
> >> > > >>compression/decompression (I mean that you write or read several
> >> > > >> files from
> >> > > >>single archive file) I would be much surprised if at least writing
> >> > > >> will not
> >> > > >>work.
> >> > > >
> >> > > >This is a likely issue, but fortunately it would not prevent all use
> >> > > > cases.
> >> > > >
> >> > > >>I wonder if there is other solution: zip could be protocol as it is
> >> > > >> now, it
> >> > > >>allows to benefit from list API and gives flexibility other demuxers
> >> > > >> to
> >> > > >>benefit from it. There could also be a "directory" demuxer which
> >> > > >> would also
> >> > > >>use that API and possibly could serve streams in your way. That
> >> > > >> demuxer
> >> > > >>could also handle directories over any protocol that supports that
> >> > > >> API.
> >> > > >
> >> > > >That was the kind of idea that I had. But I believe that to get that
> >> > > > working
> >> > > >a bit reliably, we will need to extend the directory listing
> >> > > > callbacks to
> >> > > >allow a URL context to create new URL contexts, to open remote files
> >> > > > without
> >> > > >establishing a new connection (and it will also be necessary for
> >> > > > network
> >> > > >servers). Some kind of VFS API, then.
> >> >
> >> > Agree.
> >> >
> >> > > This can be even harder as opening archive file require stat or other
> >> > > smart
> >> > > way to check some candidates that ought to be a archive file. See
> >> > > below.
> >> >
> >> > > >>>ffplay zip:///tmp/outer.zip/tmp/inner.zip/tmp/data.bin
> >> > > >>libzip can't handle it (the same way it cannot handle files via
> >> > > >> protocols),
> >> > > >>maybe libarchive will be better
> >> > > >
> >> > > >I think you misunderstood the question. I was not asking whether it
> >> > > > would be
> >> > > >able to decode nested files, but how your code did split nested
> >> > > > paths: would
> >> > > >it try to find /tmp/inner.zip/tmp/data.bin inside /tmp/outer.zip, or
> >> > > >/tmp/data.bin inside /tmp/outer.zip/tmp/inner.zip (assuming someone
> >> > > > was
> >> > > >stupid enough to name a directory dot-zip)?
> >> > >
> >> > > I assumed it is local file (no other option so far). So I stat full
> >> > > path
> >> > > (/tmp/outer.zip/tmp/inner.zip/tmp/data.bin) for being a file, if so
> >> > > then I
> >> > > opened it as zip file and used fallback to open first file.
> >> > > If not then I stat by path components: /tmp/, /tmp/outer.zip, and so
> >> > > on...
> >> > > /tmp/outer.zip is a file so I open it and treat rest of the uri as a
> >> > > path
> >> > > inside zip.
> >> >
> >> > walking the path means that the archive protocol must know about the
> >> > syntax of the underlying protocol (file, http, ftp, etc.). that seems
> >> > messy.
> >> > also inefficient if you have got to walk a long ftp path.
> >> >
> >> > wouldn't we be better off defining a special character that seperates
> >> > the zip
> >> > path from the inner path. obviously we'd need some way of escaping the
> >> > character
> >> > if it is legitimately part of either path.
> >> >
> >> > ffplay /tmp/amovie.zip
> >> > ffplay http://subtitles.org/amovie.zip#amovie.srt
> >> >
> >> > the syntax should support nested archives (even if the libzip/archive
> >> > cannot handle
> >> > that yet). e.g.
> >> >
> >> > ffplay /tmp/amovie.rar#/tmp/amovie.zip#amovie.srt
> >> >
> >> > -- Peter
> >> > (A907 E02F A6E5 0CD2 34CD 20D2 6760 79C5 AC40 DD6B)
> >>
> >> No. '#' is perfectly allowed in URLs and local filenames.
> >
> > of course it is, hence my qualification above:
> >>> obviously we'd need some way of escaping the character
> >
> > so if '##' reduces to '#', then:
> > ffplay /tmp/amovie##1.zip#amovie##1.srt  would open 'amovie#1.srt' inside
> > '/tmp/amovie#1.zip'
> >
> > '#' was only given as an example.
> > pick a character (or character sequence) that is easy to type, but
> > infrequently used in
> > uris/filenames, such to avoid having to escape to often.
> 
> How about:
>   ffplay /tmp/amovie1.zip//amovie.srt
> 
> Aka, using double directory separator to indicate diving into an archive.
> This way "ffplay /tmp/amovie1.zip/amovie" would imply amovie1.zip is directory.

You forgot // in your second example? Anyway, you can name a directory
amovie1.zip, and then "/tmp/amovie1.zip//amovie.srt" is a perfectly
valid unix path. Multiple slashes are coalesced into 1.