test5.2.c

这个是学习嵌入式开发的重要例子

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/stat.h>
#include <fcntl.h>

#define BUFFER_SIZE	1024
#define	FIFO	"/tmp/fifo.test"

void consumer_process_main(void);
void parent_process_main(void);

int main(int argc, char **argv)
{
  consumer_process_main();

  return 0;
}

void consumer_process_main(void)
{
  int fd;

  //fd = open(FIFO, O_RDONLY | O_NONBLOCK);
  fd = open(FIFO, O_RDONLY);

  sleep(10);

  if (fd < 0)
  {
    fprintf(stderr, "[%d]open FIFO %s for reading failed: %s\n", getpid(), FIFO, strerror(errno));
    return;
  }
  else
  {
    fprintf(stdout, "[%d]open FIFO %s for reading successed, fd = %d\n", getpid(), FIFO, fd);
    //sleep(10);
    //close(fd);
  }

  //sleep(100);
  fprintf(stdout, "[%d]Read data from pipe, fd = %d\n", getpid(), fd);

  char buf[BUFFER_SIZE];
  ssize_t n;

  memset(buf, 0, BUFFER_SIZE);
  // ssize_t read(int fildes, void *buf, size_t nbyte);
  n = read(fd, buf, BUFFER_SIZE);

  if (n < 0)
  {
    fprintf(stdout, "[%d]Read from pipe failed: %s\n", getpid(), strerror(errno));
    // FIXME: handle read error
  }
  else if (n == 0)
  {
    fprintf(stdout, "[%d]Read from pipe return 0.\n", getpid());
  }
  else
  {
    fprintf(stdout, "[%d]Read %d bytes from pipe.\n", getpid(), n);
    fprintf(stdout, "[%d]Message: %s\n", getpid(), buf);

    if (strlen(buf) < 8)
    {
      fprintf(stdout, "[%d]Can not get data length.\n", getpid());
      // FIXME: read rest data.
    }
    else
    {
      int length;
      char str[BUFFER_SIZE];

      memset(str, 0, BUFFER_SIZE);
      memcpy(str, buf, 8);

      length = atoi(str);

      if ((strlen(buf)) < 8 + length)
      {
	fprintf(stdout, "[%d]There's no enough data for parsing", getpid());
	// FIXME: read rest data
      }
      else
      {
	fprintf(stdout, "[%d]We have read all required data.\n", getpid());
      }
    }
  }

  close(fd);
}