stdio/sys5/fopen.c

/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License, Version 1.0 only
 * (the "License").  You may not use this file except in compliance
 * with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */
/*      Copyright (c) 1984 AT&T */
/*        All Rights Reserved   */

#pragma ident   "%Z%%M% %I% %E% SMI"

/*LINTLIBRARY*/

#include <stdio.h>
#include <fcntl.h>

extern FILE *_findiop();
static FILE *_endopen();

FILE *
fopen(char *file, char *mode)
{
    return (_endopen(file, mode, _findiop()));
}

FILE *
freopen(char *file, char *mode, FILE *iop)
{
    (void) fclose(iop); /* doesn't matter if this fails */
    return (_endopen(file, mode, iop));
}

static FILE *
_endopen(char *file, char *mode, FILE *iop)
{
    int plus, oflag, fd;

    if (iop == NULL || file == NULL || file[0] == '\0')
        return (NULL);
    plus = (mode[1] == '+');
    switch (mode[0]) {
    case 'w':
        oflag = (plus ? O_RDWR : O_WRONLY) | O_TRUNC | O_CREAT;
        break;
    case 'a':
        oflag = (plus ? O_RDWR : O_WRONLY) | O_APPEND | O_CREAT;
        break;
    case 'r':
        oflag = plus ? O_RDWR : O_RDONLY;
        break;
    default:
        return (NULL);
    }
    if ((fd = open(file, oflag, 0666)) < 0)
        return (NULL);
    iop->_cnt = 0;
    iop->_file = fd;
    iop->_flag = plus ? _IORW : (mode[0] == 'r') ? _IOREAD : _IOWRT;
    if (mode[0] == 'a')   {
        if (!plus)  {
            /* if update only mode, move file pointer to the end
               of the file */
            if ((lseek(fd,0L,2)) < 0)  {
                (void) close(fd);
                return NULL;
            }
        }
    }
    iop->_base = iop->_ptr = NULL;
    iop->_bufsiz = 0;
    return (iop);
}