aio_test.cc

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

int main()
{
  io_context_t ctx;
  unsigned nr_events = 10;
  memset(&ctx, 0, sizeof(ctx)); // It's necessary，这里一定要的
  int errcode = io_setup(nr_events, &ctx);
  if (errcode == 0) {
    printf("io_setup success\n");
  } else {
    printf("io_setup error: :%d:%s\n", errcode, strerror(-errcode));
  }

  // 如果不指定O_DIRECT，则io_submit操作和普通的read/write操作没有什么区别了，将来的LINUX可能
  // 可以支持不指定O_DIRECT标志
  int fd = open("./direct.txt", O_CREAT|O_DIRECT|O_WRONLY, S_IRWXU|S_IRWXG|S_IROTH);
  printf("open: %s\n", strerror(errno));

  char* buf;
  long page_size = sysconf(_SC_PAGESIZE);
  errcode = posix_memalign((void**)&buf, page_size, page_size);
  printf("posix_memalign: %s\n", strerror(errcode));

  strcpy(buf, "hello xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx");

  struct iocb *iocbpp = (struct iocb *)malloc(sizeof(struct iocb));
  memset(iocbpp, 0, sizeof(struct iocb));

  iocbpp[0].data = buf;
  iocbpp[0].aio_lio_opcode = IO_CMD_PWRITE;
  iocbpp[0].aio_reqprio = 0;
  iocbpp[0].aio_fildes = fd;

  iocbpp[0].u.c.buf = buf;
  iocbpp[0].u.c.nbytes = page_size;//strlen(buf); // 这个值必须按512字节对齐
  iocbpp[0].u.c.offset = 0; // 这个值必须按512字节对齐

  // 提交异步操作，异步写磁盘
  int n = io_submit(ctx, 1, &iocbpp);
  printf("==io_submit==: %d:%s\n", n, strerror(errno));

  struct io_event events[10];
  struct timespec timeout = {1, 100};
  // 检查写磁盘情况，类似于epoll_wait或select
  n = io_getevents(ctx, 1, 10, events, &timeout);
  printf("io_getevents: %d:%s\n", n, strerror(errno));

  close(fd);
  io_destroy(ctx);
  return 0;
}