On Wed, Oct 18, 2006 at 08:27:07PM +0100, Nicholas J Humfrey wrote:
> I am working on replacing the old bug-ridden HTTP code in mpg123 with
> something a bit better and then thought that perhaps I should be
> using libcurl instead. It would also give us https and lots of other
> protocols for free..
>
> Currently we have a function or two that establishes the HTTP
> connection, and then normal file IO code is used to read in the MPEG
> Audio from the socket for decoding. Is something like this possible
> with libcurl?
>
> All the examples I have seen on the website use callback functions
> and intermediate buffers, which I would ideally like to avoid (and
> keep the memory footprint down). While having a buffer would help
> with network stalls, reading MPEG Audio directly from the network
> socket has always worked quite well in mpg123.

This paradigm doesn't quite match libcurl's as the latter expects to
perform all the low-level grunt transfer work itself. This allows it to
handle compression, chunked transfers, and encryption itself and avoid
burdening the application with knowledge of all those areas. The mpg123
situation where it reads raw data directly from a descriptor only works if
the data is not encoded in any way. If you want any of libcurl's data
transformation options, then the raw descriptor approach will fail.

Having said that, it is possible to use various libcurl options to force
a raw, unencoded transfer, and there is now an option to obtain the
socket being used by libcurl, so you could almost do what you want. The
big problem is that libcurl reads data in big chunks, so it will usually
gobble up the first chunk of MP3 data before the socket can be passed
to the app. You could get around this by modifying libcurl to do 1 byte
reads until it reaches the end of the headers.

But there's little point in doing all that. libcurl would simply be
reduced to opening a socket and sending some HTTP headers across the line,
tasks that mpg123 is doing already (ok, a few other tasks could still be
handled by libcurl, such as authentication and tunneling through
proxy servers). But you gain much more versatility by changing mpg123 to
conform to libcurl, rather than the other way around.

>>> Dan

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