port/stdio/_findbuf.c

/*
 * 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   */

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


#define _LARGEFILE64_SOURCE 1

#include "lint.h"
#include "file64.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 = -1;

    struct stat64 stbuf;        /* used to get file system block size */

    if (iop->_flag & _IONBF)    /* need a small buffer, at least */
    {
    trysmall:;
        size = _SMBFSZ - PUSHBACK;
        if (fd < _NFILE)
            buf = _smbuf[fd];
        else if ((buf = (Uchar *)malloc(_SMBFSZ * sizeof (Uchar))) !=
            NULL)
            iop->_flag |= _IOMYBUF;
    }
#ifndef _STDIO_ALLOCATE
    else if (fd < 2 && (tty = isatty(fd))) {
        buf = (fd == 0) ? _sibuf : _sobuf; /* special buffer */
                        /* for std{in,out} */
    }
#endif
    else {
        /*
         * The operating system can tell us the
         * right size for a buffer;
         * avoid 0-size buffers as returned for some
         * special files (doors)
         */
        if (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 != -1) ? tty : isatty(fd)))
        iop->_flag |= _IOLBF;
    return (endbuf);
}