usr/src/lib/libc/stdio/makebuf.c

/*-
 * Copyright (c) 1990 The Regents of the University of California.
 * All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Chris Torek.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *      This product includes software developed by the University of
 *      California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#if defined(LIBC_SCCS) && !defined(lint)
static char sccsid[] = "@(#)makebuf.c   5.2 (Berkeley) 2/24/91";
#endif /* LIBC_SCCS and not lint */

#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include "local.h"

/*
 * Allocate a file buffer, or switch to unbuffered I/O.
 * Per the ANSI C standard, ALL tty devices default to line buffered.
 *
 * As a side effect, we set __SOPT or __SNPT (en/dis-able fseek
 * optimisation) right after the fstat() that finds the buffer size.
 */
void
__smakebuf(fp)
        register FILE *fp;
{
        register size_t size, couldbetty;
        register void *p;
        struct stat st;

        if (fp->_flags & __SNBF) {
                fp->_bf._base = fp->_p = fp->_nbuf;
                fp->_bf._size = 1;
                return;
        }
        if (fp->_file < 0 || fstat(fp->_file, &st) < 0) {
                couldbetty = 0;
                size = BUFSIZ;
                /* do not try to optimise fseek() */
                fp->_flags |= __SNPT;
        } else {
                couldbetty = (st.st_mode & S_IFMT) == S_IFCHR;
                size = st.st_blksize <= 0 ? BUFSIZ : st.st_blksize;
                /*
                 * Optimise fseek() only if it is a regular file.
                 * (The test for __sseek is mainly paranoia.)
                 */
                if ((st.st_mode & S_IFMT) == S_IFREG &&
                    fp->_seek == __sseek) {
                        fp->_flags |= __SOPT;
                        fp->_blksize = st.st_blksize;
                } else
                        fp->_flags |= __SNPT;
        }
        if ((p = malloc(size)) == NULL) {
                fp->_flags |= __SNBF;
                fp->_bf._base = fp->_p = fp->_nbuf;
                fp->_bf._size = 1;
        } else {
                __cleanup = _cleanup;
                fp->_flags |= __SMBF;
                fp->_bf._base = fp->_p = p;
                fp->_bf._size = size;
                if (couldbetty && isatty(fp->_file))
                        fp->_flags |= __SLBF;
        }
}