62 lines
1.5 KiB
C
62 lines
1.5 KiB
C
/* asyn_read() Author: Kees J. Bot
|
|
* 7 Jul 1997
|
|
*/
|
|
#include "asyn.h"
|
|
#include <signal.h>
|
|
|
|
ssize_t asyn_read(asynchio_t *asyn, int fd, void *buf, size_t len)
|
|
/* Asynchronous read(). Try if a read can be done, if not then set a flag
|
|
* indicating that select(2) should look out for it. Returns like a normal
|
|
* read or returns -1 with errno set to EAGAIN.
|
|
*/
|
|
{
|
|
asynfd_t *afd;
|
|
|
|
/* Asyn_wait() may block if this counter equals zero indicating that
|
|
* all of the asyn_* functions are "in progress".
|
|
*/
|
|
asyn->asyn_more++;
|
|
|
|
if ((unsigned) fd >= FD_SETSIZE) { errno= EBADF; return -1; }
|
|
afd= &asyn->asyn_afd[fd];
|
|
|
|
/* If this is the first async call on this filedescriptor then
|
|
* remember its file flags.
|
|
*/
|
|
if (!afd->afd_seen) {
|
|
if ((afd->afd_flags= fcntl(fd, F_GETFL)) < 0) return -1;
|
|
afd->afd_seen= 1;
|
|
}
|
|
|
|
/* Try to read if I/O is pending. */
|
|
if (afd->afd_state[SEL_READ] == PENDING) {
|
|
sigset_t mask;
|
|
ssize_t result;
|
|
int err;
|
|
|
|
sigemptyset(&mask);
|
|
if (sigprocmask(SIG_SETMASK, &mask, &mask) < 0) return -1;
|
|
(void) fcntl(fd, F_SETFL, afd->afd_flags | O_NONBLOCK);
|
|
|
|
/* Try the actual read. */
|
|
result= read(fd, buf, len);
|
|
err= errno;
|
|
|
|
(void) fcntl(fd, F_SETFL, afd->afd_flags);
|
|
(void) sigprocmask(SIG_SETMASK, &mask, nil);
|
|
|
|
errno= err;
|
|
if (result != -1 || errno != EAGAIN) {
|
|
afd->afd_state[SEL_READ]= IDLE;
|
|
return result;
|
|
}
|
|
}
|
|
|
|
/* Record this read as "waiting". */
|
|
afd->afd_state[SEL_READ]= WAITING;
|
|
FD_SET(fd, &asyn->asyn_fdset[SEL_READ]);
|
|
errno= EAGAIN;
|
|
asyn->asyn_more--;
|
|
return -1;
|
|
}
|