如何在LINUX下编写关于CD-ROM的程序（2）
-如何播放，暂停，停止CD
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译者：Bigluo
有几个结构是来用描述CD音轨的确切位置的，他们是struct cdrom_tochdr和struct cdrom_ti，struct cdrom_msf。
前者，当使用CDROMREADTOCHDR命令字的时候，返回第一道音轨和最后一道音轨的标号。后者，当使用CDROMPLAYTRKIND
命令字的时候，可以用来播放一段音轨的特定范围，当然也可以用来在音轨的特定地方暂停或停止播放。第三个，当使用CDROMPLAYMSF命令字的时候，可以指定CD在X分X秒时的具体位置。
struct cdrom_tochdr
{
u_char cdth_trk0; /* start track */
u_char cdth_trk1; /* end track */
};
struct cdrom_ti
{
u_char cdti_trk0; /* start track */
u_char cdti_ind0; /* start index */
u_char cdti_trk1; /* end track */
u_char cdti_ind1; /* end index */
};
struct cdrom_msf
{
u_char cdmsf_min0; /* start minute */
u_char cdmsf_sec0; /* start second */
u_char cdmsf_frame0; /* start frame */
u_char cdmsf_min1; /* end minute */
u_char cdmsf_sec1; /* end second */
u_char cdmsf_frame1; /* end frame */
};
下面的程序将从头到尾的播放一张CD：
#define CDDEVICE \"/dev/cdrom\"
struct cdrom_tochdr header;
struct cdrom_ti index;
int cdrom;
cdrom = open(CDDEVICE,O_RDONLY); // Open device
ioctl(cdrom,CDROMREADTOCHDR,(void *) &header); // Get start and end tracks
index.cdti_trk0=header.cdth_trk0; // Set first track
index.cdti_ind0=0; // Start of track
index.cdti_trk1=header.cdth_trk1; // Set final track
index.cdti_ind1=255; // End of track
iotcl(cdrom,CDROMPLAYTRKIND,(void *) &index); // Play the tracks
Pausing, resuming, stopping and ejecting are done with ioctl calls using CDROMPAUSE, CDROMRESUME, CDROMSTOP and CDROMEJECT respectively:
ioctl(cdrom,CDROMPAUSE,0); // Pause CD play.
ioctl(cdrom,CDROMRESUME,0); // Resume CD play from where it was paused.
ioctl(cdrom,CDROMSTOP,0); // Stop CD play (can\"t be RESUMEd)
ioctl(cdrom,CDROMEJECT,0); // Eject CD tray.
发布人:Bigluo 来自:Linux技术指南