play.c

CD驱动器实现的源代码

/*
 * 代码清单4: play.c
 */
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/cdrom.h>

/* CD驱动器对应的设备文件 */
#define DEVICE "/dev/cdrom"

int main() 
{
  int fd;
  int status;
  int start_min, start_sec, start_frame;/* 播放起始地址 */
  int end_min, end_sec, end_frame;	/* 播放结束地址 */
  struct cdrom_tocentry entry; 	/* TOC条目 */
  struct cdrom_msf region; 	/* 播放区域 */

  /* 打开设备 */
  fd = open(DEVICE, O_RDONLY);
  if (fd < 0) {
    perror("unable to open " DEVICE);
    exit(1);
  }

  /* 计算播放起始点的地址 */
  entry.cdte_track = 1;
  entry.cdte_format = CDROM_MSF; /* 采用MSF格式地址 */
  status = ioctl(fd, CDROMREADTOCENTRY, &entry);
  if (status != 0) {
    perror("CDROMREADTOCENTRY ioctl failed");
    exit(1);
  }
  start_min = entry.cdte_addr.msf.minute;
  start_sec = entry.cdte_addr.msf.second;
  start_frame = entry.cdte_addr.msf.frame;

  /* 计算播放结束点的地址 */
  entry.cdte_track = 2;
  status = ioctl(fd, CDROMREADTOCENTRY, &entry);
  if (status != 0) {
    perror("CDROMREADTOCENTRY ioctl failed");
    exit(1);
  }
  end_min = entry.cdte_addr.msf.minute;
  end_sec = entry.cdte_addr.msf.second;
  end_frame = entry.cdte_addr.msf.frame;

  /* 指明播放区域 */
  region.cdmsf_min0 = start_min;
  region.cdmsf_sec0 = start_sec;
  region.cdmsf_frame0 = start_frame;
  region.cdmsf_min1 = end_min;
  region.cdmsf_sec1 = end_sec;
  region.cdmsf_frame1 = end_frame;

  /* 播放 */
  status = ioctl(fd, CDROMPLAYMSF, &region);
  if (status != 0) {
    perror("CDROMPLAYMSF ioctl failed");
    exit(1);
  }  

  /* 关闭设备 */
  status = close(fd);
  if (status != 0) {
    perror("unable to close " DEVICE);
    exit(1);
  }

  return 0;
}