Writing with OggzHungry callbacks

You can add packets to the Oggz packet queue only when it is "hungry" by providing an OggzHungry callback.

You can add packets to the Oggz packet queue only when it is "hungry" by providing an OggzHungry callback.

An OggzHungry callback will:

• Create an ogg_packet structure
• Add it to the packet queue with oggz_write_feed()

Once you have set such a callback with oggz_write_set_hungry_callback(), simply call oggz_write() or oggz_write_output() repeatedly, and Oggz will call your callback to provide packets when it is hungry.

This process is illustrated in the following diagram:

The following example code generates a stream of ten packets, each containing a single byte ('A', 'B', ... , 'J'):

 
#include <stdlib.h> /* exit */
#include "oggz/oggz.h"
 
/*
** Inspiration : http://sourcefrog.net/weblog/software/languages/C/unused.html
*/
#ifdef UNUSED
#elif defined (__GNUC__)
#       define UNUSED(x) UNUSED_ ## x __attribute__ ((unused))
#elif defined (__LCLINT__)
#       define UNUSED(x) /*@unused@*/ x
#else
#       define UNUSED(x) x
#endif
 
static long serialno;
static ogg_int64_t granulepos = 0;
static ogg_int64_t packetno = 0;
 
static int
hungry (OGGZ * oggz, int UNUSED(empty), void * UNUSED(user_data))
{
  ogg_packet op;
  unsigned char buf[1];
 
  buf[0] = 'A' + (int)packetno;
 
  op.packet = buf;
  op.bytes = 1;
  op.granulepos = granulepos;
  op.packetno = packetno;
 
  if (packetno == 0) op.b_o_s = 1;
  else op.b_o_s = 0;
 
  if (packetno == 9) op.e_o_s = 1;
  else op.e_o_s = 0;
 
  oggz_write_feed (oggz, &op, serialno, OGGZ_FLUSH_AFTER, NULL);
 
  granulepos += 100;
  packetno++;
 
  return 0;
}
 
int
main (int argc, char * argv[])
{
  char * progname, * filename = NULL;
  OGGZ * oggz;
  long n;
 
  progname = argv[0];
  if (argc > 1) filename = argv[1];
 
  if (filename) {
    oggz = oggz_open (filename, OGGZ_WRITE);
  } else {
    oggz = oggz_open_stdio (stdout, OGGZ_WRITE);
  }
 
  if (oggz == NULL) {
    fprintf (stderr, "%s: Error creating oggz\n", progname);
    exit (1);
  }
 
  serialno = oggz_serialno_new (oggz);
 
  if (oggz_write_set_hungry_callback (oggz, hungry, 1, NULL) == -1) {
    fprintf (stderr, "%s: Error setting OggzHungry callback\n", progname);
    exit (1);
  }
 
  while ((n = oggz_write (oggz, 32)) > 0);
 
  oggz_close (oggz);
 
  exit (0);
}