src/common/fd.c

/*****************************************************************************\
 *  $Id$
 *****************************************************************************
 *  Copyright (C) 2001-2002 The Regents of the University of California.
 *  Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
 *  Written by Chris Dunlap <cdunlap@llnl.gov>.
 *  UCRL-CODE-2002-009.
 *  
 *  This file is part of ConMan, a remote console management program.
 *  For details, see <http://www.llnl.gov/linux/conman/>.
 *  
 *  ConMan is free software; you can redistribute it and/or modify it under
 *  the terms of the GNU General Public License as published by the Free
 *  Software Foundation; either version 2 of the License, or (at your option)
 *  any later version.
 *
 *  In addition, as a special exception, the copyright holders give permission 
 *  to link the code of portions of this program with the OpenSSL library under 
 *  certain conditions as described in each individual source file, and 
 *  distribute linked combinations including the two. You must obey the GNU 
 *  General Public License in all respects for all of the code used other than 
 *  OpenSSL. If you modify file(s) with this exception, you may extend this 
 *  exception to your version of the file(s), but you are not obligated to do 
 *  so. If you do not wish to do so, delete this exception statement from your
 *  version.  If you delete this exception statement from all source files in 
 *  the program, then also delete it here.
 *  
 *  ConMan is distributed in the hope that it will be useful, but WITHOUT ANY
 *  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
 *  FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
 *  details.
 *  
 *  You should have received a copy of the GNU General Public License along
 *  with ConMan; if not, write to the Free Software Foundation, Inc.,
 *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301  USA.
 *****************************************************************************
 *  Refer to "fd.h" for documentation on public functions.
\*****************************************************************************/


#ifdef HAVE_CONFIG_H
#  include "config.h"
#endif /* HAVE_CONFIG_H */

#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>

#include "src/common/macros.h"
#include "src/common/fd.h"
#include "src/common/log.h"

/*
 * Define slurm-specific aliases for use by plugins, see slurm_xlator.h 
 * for details. 
 */
strong_alias(fd_read_n,		slurm_fd_read_n);
strong_alias(fd_write_n,	slurm_fd_write_n);
strong_alias(fd_set_blocking,	slurm_fd_set_blocking);
strong_alias(fd_set_nonblocking,slurm_fd_set_nonblocking);


static int fd_get_lock(int fd, int cmd, int type);
static pid_t fd_test_lock(int fd, int type);


void fd_set_close_on_exec(int fd)
{
    assert(fd >= 0);

    if (fcntl(fd, F_SETFD, FD_CLOEXEC) < 0)
        error("fcntl(F_SETFD) failed: %m");
    return;
}

void fd_set_noclose_on_exec(int fd)
{
    assert(fd >= 0);

    if (fcntl(fd, F_SETFD, 0) < 0)
        error("fcntl(F_SETFD) failed: %m");
    return;
}

int fd_is_blocking(int fd)
{
    int val = 0;

    assert(fd >= 0);

    if ((val = fcntl(fd, F_GETFL, 0)) < 0)
	error("fnctl(F_GET_FL) failed: %m");
    return (val & O_NONBLOCK) ? 0 : 1;
}

void fd_set_nonblocking(int fd)
{
    int fval;

    assert(fd >= 0);

    if ((fval = fcntl(fd, F_GETFL, 0)) < 0)
        error("fcntl(F_GETFL) failed: %m");
    if (fcntl(fd, F_SETFL, fval | O_NONBLOCK) < 0)
        error("fcntl(F_SETFL) failed: %m");
    return;
}

void fd_set_blocking(int fd)
{
    int fval;

    assert(fd >= 0);

    if ((fval = fcntl(fd, F_GETFL, 0)) < 0)
	    error("fcntl(F_GETFL) failed: %m");
    if (fcntl(fd, F_SETFL, fval & ~O_NONBLOCK) < 0)
	    error("fcntl(F_SETFL) failed: %m");
    return;
}


int fd_get_read_lock(int fd)
{
    return(fd_get_lock(fd, F_SETLK, F_RDLCK));
}


int fd_get_readw_lock(int fd)
{
    return(fd_get_lock(fd, F_SETLKW, F_RDLCK));
}


int fd_get_write_lock(int fd)
{
    return(fd_get_lock(fd, F_SETLK, F_WRLCK));
}


int fd_get_writew_lock(int fd)
{
    return(fd_get_lock(fd, F_SETLKW, F_WRLCK));
}


int fd_release_lock(int fd)
{
    return(fd_get_lock(fd, F_SETLK, F_UNLCK));
}


pid_t fd_is_read_lock_blocked(int fd)
{
    return(fd_test_lock(fd, F_RDLCK));
}


pid_t fd_is_write_lock_blocked(int fd)
{
    return(fd_test_lock(fd, F_WRLCK));
}


static int fd_get_lock(int fd, int cmd, int type)
{
    struct flock lock;

    assert(fd >= 0);

    lock.l_type = type;
    lock.l_start = 0;
    lock.l_whence = SEEK_SET;
    lock.l_len = 0;

    return(fcntl(fd, cmd, &lock));
}


static pid_t fd_test_lock(int fd, int type)
{
    struct flock lock;

    assert(fd >= 0);

    lock.l_type = type;
    lock.l_start = 0;
    lock.l_whence = SEEK_SET;
    lock.l_len = 0;
    lock.l_pid = 0;	/* avoid valgrind error */

    if (fcntl(fd, F_GETLK, &lock) < 0)
        error("Unable to test for file lock: %m");
    if (lock.l_type == F_UNLCK)
        return(0);
    return(lock.l_pid);
}


ssize_t fd_read_n(int fd, void *buf, size_t n)
{
    size_t nleft;
    ssize_t nread;
    unsigned char *p;

    p = buf;
    nleft = n;
    while (nleft > 0) {
        if ((nread = read(fd, p, nleft)) < 0) {
            if (errno == EINTR)
                continue;
            else
                return(-1);
        }
        else if (nread == 0) {          /* EOF */
            break;
        }
        nleft -= nread;
        p += nread;
    }
    return(n - nleft);
}


ssize_t fd_write_n(int fd, void *buf, size_t n)
{
    size_t nleft;
    ssize_t nwritten;
    unsigned char *p;

    p = buf;
    nleft = n;
    while (nleft > 0) {
        if ((nwritten = write(fd, p, nleft)) < 0) {
            if (errno == EINTR)
                continue;
            else
                return(-1);
        }
        nleft -= nwritten;
        p += nwritten;
    }
    return(n);
}


ssize_t fd_read_line(int fd, void *buf, size_t maxlen)
{
    ssize_t n, rc;
    unsigned char c, *p;

    n = 0;
    p = buf;
    while (n < maxlen - 1) {            /* reserve space for NUL-termination */

        if ((rc = read(fd, &c, 1)) == 1) {
            n++;
            *p++ = c;
            if (c == '\n')
                break;                  /* store newline, like fgets() */
        }
        else if (rc == 0) {
            if (n == 0)                 /* EOF, no data read */
                return(0);
            else                        /* EOF, some data read */
                break;
        }
        else {
            if (errno == EINTR)
                continue;
            return(-1);
        }
    }

    *p = '\0';                          /* NUL-terminate, like fgets() */
    return(n);
}