src/lib/file-lock.c

	file-lock.c revision 2767104d81e97a109f0aa9758792bfa1da325a97
/* Copyright (c) 2002-2003 Timo Sirainen */

#include "lib.h"
#include "file-lock.h"

#include <time.h>
#include <signal.h>

int file_try_lock(int fd, int lock_type)
{
    return file_wait_lock_full(fd, lock_type, 0, NULL, NULL);
}

int file_wait_lock(int fd, int lock_type)
{
    return file_wait_lock_full(fd, lock_type, DEFAULT_LOCK_TIMEOUT,
                   NULL, NULL);
}

int file_wait_lock_full(int fd, int lock_type, unsigned int timeout,
            void (*callback)(unsigned int secs_left, void *context),
            void *context)
{
    struct flock fl;
    time_t timeout_time, now;
    unsigned int next_alarm;

    if (timeout == 0)
        timeout_time = 0;
    else {
        timeout_time = time(NULL) + timeout;
        alarm(I_MIN(timeout, 5));
    }

    fl.l_type = lock_type;
    fl.l_whence = SEEK_SET;
    fl.l_start = 0;
    fl.l_len = 0;

    while (fcntl(fd, timeout != 0 ? F_SETLKW : F_SETLK, &fl) < 0) {
        if (timeout == 0 && (errno == EACCES || errno == EAGAIN)) {
            alarm(0);
            return 0;
        }

        if (errno != EINTR) {
            alarm(0);
            return -1;
        }

        now = time(NULL);
        if (timeout != 0 && now >= timeout_time) {
            errno = EAGAIN;
            alarm(0);
            return 0;
        }

        next_alarm = (timeout_time - now) % 5;
        if (next_alarm == 0)
            next_alarm = 5;
        alarm(next_alarm);

        if (callback != NULL)
            callback(timeout_time - now, context);
    }

    alarm(0);
    return 1;
}