[Libcdio-help] Custom read_audio function

[Bastiaan Timmer]

Hi!

After reading an old message on this mailing list 
(http://lists.gnu.org/archive/html/libcdio-devel/2008-02/msg00001.html) 
I wrote a custom read_audio function for ripping audio cd's. The read function 
basically looks like this:

long readRaw2448(cdrom_drive_t *drive, void *pbuf, lsn_t firstsector, long 
sectors)
{
  // ... do some allocations ...

  driver_return_code_t ret;
  if ((ret = mmc_read_cd(drive->p_cdio, s_buffer, firstsector, 
CDIO_MMC_READ_TYPE_ANY, false, false, 
                         0, true, false, false, 1, s_buffersize, sectors)) != 
DRIVER_OP_SUCCESS)
  {
    std::cout << "RETURN CODE: " << ret << std::endl;
    return ret; // will be negative if we get here
  }

  // ... handle the data (handle subframe, copy audio into pbuf) ...

  return sectors;

}

Then, I simply set cdrom_drive_t.read_audio to this function, and read a cd 
with a loop nearly identical to the one 
used in the paranoia.c example:

for (i_cursor = i_first_lsn; i_cursor <= i_last_lsn; i_cursor ++)
{
  int16_t *p_readbuf = paranoia_read(p, callback);
  if (!p_readbuf)
  {
    std::cout << "Failed to read frame" << std::endl;
    return false;
  else
  {
    std::cout << "Got frame" << std::endl;
    // ... handle returned frame ...
  }
}

Now this all worked splendidly, but yesterday I wrote another custom read 
function to be used in some other 
circumstances. This time, I made a slight mistake in the mmc command, causing 
mmc_read_cd() to fail and return 
DRIVER_OP_BAD_PARAMETER. Now I had never seen the read function fail before, 
but simply assumed that if the 
read_audio function would not return a number of sectors, but a negative value 
(an error), paranoia_read() would 
return NULL so that the cd reading loop would break (the 'if (!p_readbuf)' 
part). Instead, I just get the 
following messages repeated:

[MESSAGE] (CdioInternal) : ioctl CDROM_SEND_PACKET failed: Invalid argument
RETURN CODE: -5
[WARNING] (CdioCddaInterface::callback()) : paranoia_read() reports `read 
error' at sector 0

The first of these is a message from a log_handler (set with 
cdio_log_set_handler()). The second is the cout seen 
in the readRaw2448() function shown above. The last is a message from my 
callback (given as parameter to 
paranoia_read()). The messages get repeated in series of 4, where the sector 
number changes from 0 to 25 to 50 to 75 
and then back to 0. Calling paranoia_read_limited() instead of paranoia_read() 
in the loop does not seem to help, 
paranoia_read() will just not return. At what point could/should I break from 
the loop if read_audio returns an error 
code? Am I returning the correct values from the read function 
(driver_return_code_t on error, sectors on success)? 
Any other remarks?

thanks,
Bas Timmer