format_flac.c

/* Icecast
 *
 * This program is distributed under the GNU General Public License, version 2.
 * A copy of this license is included with this source.
 *
 * Copyright 2010-2022, Karl Heyes <karl@kheyes.plus.com>,
 * Copyright 2000-2004, Jack Moffitt <jack@xiph.org>,
 *                      Michael Smith <msmith@xiph.org>,
 *                      oddsock <oddsock@xiph.org>,
 *                      Karl Heyes <karl@xiph.org>
 *                      and others (see AUTHORS for details).
 */


/* Ogg codec handler for FLAC logical streams */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdlib.h>
#include <ogg/ogg.h>
#include <string.h>

typedef struct source_tag source_t;

#include "refbuf.h"
#include "format_ogg.h"
#include "client.h"
#include "stats.h"
#include "global.h"

#define CATMODULE "format-flac"
#include "logging.h"


static void flac_codec_free (ogg_state_t *ogg_info, ogg_codec_t *codec)
{
    DEBUG0 ("freeing FLAC codec");
    stats_event (ogg_info->mount, "FLAC_version", NULL);
    ogg_stream_clear (&codec->os);
    format_ogg_free_cached (codec);
    free (codec);
}


/* Here, we just verify the page is ok and then add it to the queue */
static refbuf_t *process_flac_page (ogg_state_t *ogg_info, ogg_codec_t *codec, ogg_page *page)
{
    refbuf_t * refbuf;

    if (codec->headers > 0)
    {
        int loop = 20, found_header = 0, packets = 0;
        ogg_packet packet;
        if (ogg_stream_pagein (&codec->os, page) < 0)   // only put in pages during the header detection phase
        {
            ogg_info->error = 1;
            return NULL;
        }
        do
        {
            int pkt = ogg_stream_packetout (&codec->os, &packet);

            if (pkt > 0)
            {
                packets++;
                if (codec->headers)
                {
                    int type = packet.packet[0];
                    if ((type >= 0x01 && type <= 0x7E) || (type >= 0x81 && type <= 0xFE))
                    {   // valid metadata code type
                        codec->headers++;
                        found_header++;
                        continue;
                    }
                    if (type == 0x7F)
                    {   // should never be encountered
                        WARN0 ("Found another initial header packet");
                        ogg_info->error = 1;
                        return NULL;
                    }
                    // non-metadata packet
                    if (found_header)
                        WARN0 ("Found an unexpected packet with headers");
                    else
                        format_ogg_free_cached (codec); // found non-header packet, no headers outstanding
                    DEBUG1 ("header packet count %d", codec->headers);
                    codec->headers = 0;         // stop the header processing phase
                }
                continue;
            }
            if (pkt == 0) break;     // usual loop exit path
            loop--;
        } while (loop);
        if (loop == 0)
        {   // packetout can occur but abort in such repeated cases
            WARN0 ("Looping too many times, abort packetout loop");
            ogg_info->error = 1;
            return NULL;
        }
        if (packets == 0)
        {   // unlikely but possible, page added but incomplete packet
            DEBUG0 ("page cached in case of header packet");
            refbuf = make_refbuf_with_page (codec, page);
            *codec->cached_p = refbuf;
            codec->cached_p = (void*)&refbuf->associated;
            return NULL;
        }
        if (found_header)
        {
            // add any previously undetermined header pages
            format_ogg_attach_cached (codec);
            DEBUG0("Adding header page");
            format_ogg_attach_header (codec, page);
            return NULL;
        }
    }
    refbuf = make_refbuf_with_page (codec, page);
    return refbuf;
}


/* Check for flac header in logical stream */

ogg_codec_t *initial_flac_page (format_plugin_t *plugin, ogg_page *page)
{
    ogg_state_t *ogg_info = plugin->_state;
    ogg_codec_t *codec = calloc (1, sizeof (ogg_codec_t));
    ogg_packet packet;

    ogg_stream_init (&codec->os, ogg_page_serialno (page));
    ogg_stream_pagein (&codec->os, page);

    ogg_stream_packetout (&codec->os, &packet);

    DEBUG0("checking for FLAC codec");
    do
    {
        unsigned char *parse = packet.packet;
        // format 0x7F F L A C, '1' x  y y f L a C zzzzz
        // x   1 byte minor number
        // y   2 BE byte count of header packets
        // z   StreamINFO structure

        if (page->header_len + page->body_len != 79)
            break;
        if (parse[0] != 0x7F)
            break;

        if (memcmp (parse+1, "FLAC", 4) != 0)
            break;

        if (parse[5] != 1)
        {
            WARN1 ("Unknown Ogg FLAC version %d, skipping", parse[5]);
            break;
        }
        int headers = ((parse[7]<<8) + parse[8]) + 1; // include this one

        if (memcmp (parse+9, "fLaC", 4) != 0)
            break;
        INFO0 ("seen initial FLAC header");
        stats_event_args (ogg_info->mount, "FLAC_version", "%d.%d",  parse[5], parse[6]);
        if (headers)
            INFO1 ("FLAC stream reports to have %d headers", headers);
        else
            INFO0 ("FLAC stream has undefined number of headers, will check as they come in");
        codec->process_page = process_flac_page;
        codec->codec_free = flac_codec_free;
        codec->headers = 1;
        codec->parent = ogg_info;
        codec->name = "FLAC";

        format_ogg_attach_header (codec, page);
        return codec;
    } while (0);

    ogg_stream_clear (&codec->os);
    free (codec);
    return NULL;
}