/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (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 2008 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

/*      Copyright (c) 1988 AT&T */
/*        All Rights Reserved   */

/*
 * Copyright 2020 Robert Mustacchi
 * Copyright 2022 OmniOS Community Edition (OmniOSce) Association.
 */


#define _LARGEFILE64_SOURCE     1

#include "lint.h"
#include "file64.h"
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include "stdiom.h"

/*
 * If buffer space has been pre-allocated use it otherwise malloc space.
 * PUSHBACK causes the base pointer to be bumped forward. At least 4 bytes
 * of pushback are required to meet international specifications.
 * Extra space at the end of the buffer allows for synchronization problems.
 * If malloc() fails stdio bails out; assumption being the system is in trouble.
 * Associate a buffer with stream; return NULL on error.
 */
Uchar *
_findbuf(FILE *iop)
{
        int fd = _get_fd(iop);
        Uchar *buf;
        int size = BUFSIZ;
        Uchar *endbuf;
        int tty, err;

        /*
         * isatty(3C) will set errno as a side-effect of returning 0. Hide this
         * from callers so that they do not see errno changing for no apparent
         * reason.
         */
        err = errno;
        tty = isatty(fd);
        errno = err;

        if (iop->_flag & _IONBF) {      /* need a small buffer, at least */
        trysmall:
                size = _SMBFSZ - PUSHBACK;
                if (fd >= 0 && fd < _NFILE) {
                        buf = _smbuf[fd];
                } else if ((buf = (Uchar *)malloc(_SMBFSZ * sizeof (Uchar))) !=
                    NULL) {
                        iop->_flag |= _IOMYBUF;
                }
        } else if (fd >= 0 && fd < 2 && tty != 0) {
                /* Use special buffers for standard in and standard out */
                buf = (fd == 0) ? _sibuf : _sobuf;
        } else {

                /*
                 * The operating system can tell us the right size for a buffer;
                 * avoid 0-size buffers as returned for some special files
                 * (doors). Use the default buffer size for memory streams.
                 */
                struct stat64 stbuf;

                if (fd != -1 && fstat64(fd, &stbuf) == 0 && stbuf.st_blksize >
                    0) {
                        size = stbuf.st_blksize;
                }

                if ((buf = (Uchar *)malloc(sizeof (Uchar)*(size+_SMBFSZ))) !=
                    NULL) {
                        iop->_flag |= _IOMYBUF;
                } else {
                        goto trysmall;
                }
        }
        if (buf == NULL)
                return (NULL);  /* malloc() failed */
        iop->_base = buf + PUSHBACK;    /* bytes for pushback */
        iop->_ptr = buf + PUSHBACK;
        endbuf = iop->_base + size;
        _setbufend(iop, endbuf);
        if (!(iop->_flag & _IONBF) && tty != 0)
                iop->_flag |= _IOLBF;
        return (endbuf);
}