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