wbuf.c revision 331722 
1/*-
2 * Copyright (c) 1990, 1993
3 *	The Regents of the University of California.  All rights reserved.
4 *
5 * This code is derived from software contributed to Berkeley by
6 * Chris Torek.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 * 1. Redistributions of source code must retain the above copyright
12 *    notice, this list of conditions and the following disclaimer.
13 * 2. Redistributions in binary form must reproduce the above copyright
14 *    notice, this list of conditions and the following disclaimer in the
15 *    documentation and/or other materials provided with the distribution.
16 * 3. Neither the name of the University nor the names of its contributors
17 *    may be used to endorse or promote products derived from this software
18 *    without specific prior written permission.
19 *
20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
23 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
30 * SUCH DAMAGE.
31 */
32
33#if defined(LIBC_SCCS) && !defined(lint)
34static char sccsid[] = "@(#)wbuf.c	8.1 (Berkeley) 6/4/93";
35#endif /* LIBC_SCCS and not lint */
36#include <sys/cdefs.h>
37__FBSDID("$FreeBSD: stable/11/lib/libc/stdio/wbuf.c 331722 2018-03-29 02:50:57Z eadler $");
38
39#include <errno.h>
40#include <stdio.h>
41#include "local.h"
42
43/*
44 * Write the given character into the (probably full) buffer for
45 * the given file.  Flush the buffer out if it is or becomes full,
46 * or if c=='\n' and the file is line buffered.
47 *
48 * Non-MT-safe
49 */
50int
51__swbuf(int c, FILE *fp)
52{
53	int n;
54
55	/*
56	 * In case we cannot write, or longjmp takes us out early,
57	 * make sure _w is 0 (if fully- or un-buffered) or -_bf._size
58	 * (if line buffered) so that we will get called again.
59	 * If we did not do this, a sufficient number of putc()
60	 * calls might wrap _w from negative to positive.
61	 */
62	fp->_w = fp->_lbfsize;
63	if (prepwrite(fp) != 0) {
64		errno = EBADF;
65		return (EOF);
66	}
67	c = (unsigned char)c;
68
69	ORIENT(fp, -1);
70
71	/*
72	 * If it is completely full, flush it out.  Then, in any case,
73	 * stuff c into the buffer.  If this causes the buffer to fill
74	 * completely, or if c is '\n' and the file is line buffered,
75	 * flush it (perhaps a second time).  The second flush will always
76	 * happen on unbuffered streams, where _bf._size==1; fflush()
77	 * guarantees that putc() will always call wbuf() by setting _w
78	 * to 0, so we need not do anything else.
79	 */
80	n = fp->_p - fp->_bf._base;
81	if (n >= fp->_bf._size) {
82		if (__fflush(fp))
83			return (EOF);
84		n = 0;
85	}
86	fp->_w--;
87	*fp->_p++ = c;
88	if (++n == fp->_bf._size || (fp->_flags & __SLBF && c == '\n'))
89		if (__fflush(fp))
90			return (EOF);
91	return (c);
92}
93