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cdrom.cxx

#include <freedb/freedb.hxx>

#include <sys/ioctl.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>

vector<TrackPosition> Freedb::getTrackOffsets(string device = "/dev/cdrom")
{
    /* open device */
    int fd = open(device.c_str(), O_RDONLY | O_NONBLOCK);
    if (fd == (-1))
    {
        Error err;

        err.errcode = errno;
        err.errmsg = "Error while opening CD-ROM device " + device;
        err.extinfo = strerror(errno);

        throw(err);
    }

    /* read TOC to get number of tracks */
    struct cdrom_tochdr header;
    int retval = ioctl(fd, CDROMREADTOCHDR, &header);
    if (fd == (-1))
    {
        Error err;

        err.errcode = errno;
        err.errmsg = "Error while reading TOC header on " + device;
        err.extinfo = strerror(errno);

        throw(err);
    }
    int num_tracks = header.cdth_trk1;

    /* loop through tracks and save offsets */
    TrackPosition offset;
    vector<TrackPosition> offsets;
    struct cdrom_tocentry te;
    int pos_frames;

    for (int i = 0; i <= num_tracks; i++)
    {

        te.cdte_track = (i == num_tracks ? CDROM_LEADOUT : i + 1);
        te.cdte_format = CDROM_MSF;

        retval = ioctl(fd, CDROMREADTOCENTRY, &te);
        if (retval == (-1))
        {
            Error err;

            err.errcode = errno;
            err.errmsg = "Error while reading TOC entry of track " + itos(i) + " on " + device;
            err.extinfo = strerror(errno);

            throw(err);
        }

        offset.min = static_cast<int>(te.cdte_addr.msf.minute);
        offset.sec = static_cast<int>(te.cdte_addr.msf.second);
        offset.frame = static_cast<int>(te.cdte_addr.msf.frame);

        offsets.push_back(offset);
        /*
         *  To calculate the absolute frame position:
         *
         *  pos_abs = offset.frame + offset.second * CD_FRAMES + offset.minute * CD_SECS * CD_FRAMES;
         *
         *  Where CD_SECS is defined 60 and CD_FRAMES is defined 75 in linux/cdrom.h.
         */
    }

    /* done */
    return(offsets);
}

int Freedb::generateDiscSum(int n)
{
    int sum = 0;

    while (n > 0)
    {
        sum += (n % 10);
        n = n / 10;
    }

    return(sum);
}

unsigned long Freedb::generateDiscID(const vector<TrackPosition> offsets, const int num_tracks)
{
    int i = 0, t = 0, n = 0;

    while (i < num_tracks)
    {
        n += Freedb::generateDiscSum((offsets[i].min * 60) + offsets[i].sec);
        i++;
    }

    t = ((offsets[num_tracks].min * 60) + offsets[num_tracks].sec) -
        ((offsets[0].min * 60) + offsets[0].sec);

    return((n % 0xff) << 24 | t << 8 | num_tracks);
}


unsigned long Freedb::getDiscID(string device = "/dev/cdrom")
{
    vector<TrackPosition> offsets;

    try
    {
        offsets = Freedb::getTrackOffsets();
    }
    catch(const Error& err)
    {
        throw err;
    }

    int num_tracks = 0;

    vector<TrackPosition>::const_iterator i = offsets.begin();

    while (i != offsets.end())
    {
        num_tracks++;
        i++;
    }

    return(Freedb::generateDiscID(offsets, num_tracks - 1));
}

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