#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/ioctl.h>
#include <stdlib.h>
#include <stdio.h>
#include <linux/soundcard.h>

#define LENGTH 3    /* 存储秒数 */
#define RATE 22050   /* 采样频率 */
#define SIZE 8      /* 量化位数 */
#define CHANNELS 1  /* 声道数目 */

/* 用于保存数字音频数据的内存缓冲区 */
unsigned char buf[LENGTH*RATE*SIZE*CHANNELS/8];

int openDsp(int rd){
    int fd; /* 声音设备的文件描述符 */
    int arg; /* 用于ioctl调用的参数 */
    int status;   /* 系统调用的返回值 */

    /* 打开声音设备 */
    if(rd==0)
      fd= open("/dev/dsp",O_RDONLY);
    else
      fd= open("/dev/dsp",O_WRONLY);
    if (fd < 0) {
        perror("open of /dev/dsp failed");
        exit(1);
    }

    /* 设置采样时的量化位数 */
    arg = SIZE;
    status = ioctl(fd, SOUND_PCM_WRITE_BITS, &arg);
    if (status == -1)
      perror("SOUND_PCM_WRITE_BITS ioctl failed");
    if (arg != SIZE)
      perror("unable to set sample size");

      /* 设置采样时的量化位数 */
    arg = SIZE;
    status = ioctl(fd, SOUND_PCM_WRITE_BITS, &arg);
    if (status == -1)
      perror("SOUND_PCM_WRITE_BITS ioctl failed");
    if (arg != SIZE)
      perror("unable to set sample size");


    /* 设置采样时的声道数目 */
    arg = CHANNELS;
    status = ioctl(fd, SOUND_PCM_WRITE_CHANNELS, &arg);
    if (status == -1)
      perror("SOUND_PCM_WRITE_CHANNELS ioctl failed");
    if (arg != CHANNELS)
      perror("unable to set number of channels");


    /* 设置采样时的采样频率 */
    arg = RATE;
    status = ioctl(fd, SOUND_PCM_WRITE_RATE, &arg);
    if (status == -1)
      perror("SOUND_PCM_WRITE_WRITE ioctl failed");
    return fd;
}

int main()
{
    int status;
    /* 循环，直到按下Control-C */
    while (1) {
        memset(buf,0,sizeof(buf));
        int fdread=openDsp(0);
        printf("Say something:\n");
        status = read(fdread, buf, sizeof(buf)); /* 录音 */
        if (status != sizeof(buf))
          perror("read wrong number of bytes");
        status=close(fdread);
        if(status==-1){
          perror("close Read Dsp wrong");
          exit(1);
        }

        int fdwrite=openDsp(1);
        printf("You said:\n");
        status = write(fdwrite, buf, sizeof(buf)); /* 回放 */
        if (status != sizeof(buf))
          perror("wrote wrong number of bytes");

        /* 在继续录音前等待回放结束 */
        status = ioctl(fdwrite, SOUND_PCM_SYNC, 0);
        if (status == -1)
          perror("SOUND_PCM_SYNC ioctl failed");
        status=close(fdwrite);
        if(status==-1){
          perror("rclose Write Dsp wrong");
          exit(1);
        }
    }
    return 0;
}