转自：http://blog.chinaunix.net/uid-24567872-id-87677.html
首先，贴一下异步IO中用的的一些结构体，因为平常很少用，整理起来方便查看。
aio.h中的struct aiocb
| struct aiocb
{
int aio_fildes; /* File desriptor. */
int aio_lio_opcode; /* Operation to be performed. */
int aio_reqprio; /* Request priority offset. */
volatile void *aio_buf; /* Location of buffer. */
size_t aio_nbytes; /* Length of transfer. */
struct sigevent aio_sigevent; /* Signal number and value. */
/* Internal members. */
struct aiocb *__next_prio;
int __abs_prio;
int __policy;
int __error_code;
__ssize_t __return_value;
};
|
siginfo.h中的struct sigevent和union sigval
| typedef struct sigevent
{
sigval_t sigev_value;
int sigev_signo;
int sigev_notify;
union
{
int _pad[__SIGEV_PAD_SIZE];
/* When SIGEV_SIGNAL and SIGEV_THREAD_ID set, LWP ID of the
thread to receive the signal. */
__pid_t _tid;
struct
{
void (*_function) (sigval_t); /* Function to start. */
void *_attribute; /* Really pthread_attr_t. */
} _sigev_thread;
} _sigev_un;
} sigevent_t;
/* POSIX names to access some of the members. */
# define sigev_notify_function _sigev_un._sigev_thread._function
# define sigev_notify_attributes _sigev_un._sigev_thread._attribute
|
| typedef union sigval
{
int sival_int;
void *sival_ptr;
} sigval_t;
|
例子1：
| #include <aio.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <signal.h>
void async_read(int s, siginfo_t * info, void * context)
{
struct aiocb *ptr =
(struct aiocb *)info->si_value.sival_ptr;
printf("read=%s", (char *)ptr->aio_buf);
}
int main(void)
{
struct aiocb cb;
char sbuf[100];
int ret;
struct sigaction act;
sigemptyset(&act.sa_mask);
act.sa_flags = SA_RESTART | SA_SIGINFO;
act.sa_sigaction = async_read;
sigaction(SIGUSR1, &act, NULL);
bzero(&cb, sizeof(cb));
cb.aio_fildes = 0;
cb.aio_buf = sbuf;
cb.aio_nbytes = 100;
cb.aio_offset = 0;
cb.aio_sigevent.sigev_value.sival_ptr = &cb;
cb.aio_sigevent.sigev_notify = SIGEV_SIGNAL;
cb.aio_sigevent.sigev_signo = SIGUSR1;
ret = aio_read(&cb);
if (ret == -1) {
perror("aio_read");
exit(1);
}
int i = 0;
while (1) {
printf("%d\n",i++);
sleep(3);
}
return 0;
}
|
运行结果：
注意：要加相应的库，-lrt
|
$ ./gcc -o test aio_signal.c -lrt
$ ./test
0
1
h2
ell3
o
read=hello
4
^C
|
例子2：
| #include <aio.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
void async_read(sigval_t val)
{
struct aiocb *ptr =
(struct aiocb *)val.sival_ptr;
printf("read=%s", (char *)ptr->aio_buf);
}
int main(void)
{
struct aiocb cb;
char sbuf[100];
int ret;
bzero(&cb, sizeof(cb));
cb.aio_fildes = 0;
cb.aio_buf = sbuf;
cb.aio_nbytes = 100;
cb.aio_offset = 0;
cb.aio_sigevent.sigev_value.sival_ptr = &cb;
cb.aio_sigevent.sigev_notify = SIGEV_THREAD;
cb.aio_sigevent.sigev_notify_function =
async_read;
cb.aio_sigevent.sigev_notify_attributes = NULL;
ret = aio_read(&cb);
if (ret == -1) {
perror("aio_read");
exit(1);
}
int i = 0;
while (1) {
printf("%d\n",i++);
sleep(1);
}
return 0;
}
|
运行结果同上。
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