xref: /openbsd-src/lib/libc/stdio/wbuf.c (revision 33b4f39fbeffad07bc3206f173cff9f3c9901cd1)
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)
34 static char rcsid[] = "$OpenBSD: wbuf.c,v 1.6 2003/06/02 20:18:37 millert Exp $";
35 #endif /* LIBC_SCCS and not lint */
36 
37 #include <stdio.h>
38 #include <errno.h>
39 #include "local.h"
40 
41 /*
42  * Write the given character into the (probably full) buffer for
43  * the given file.  Flush the buffer out if it is or becomes full,
44  * or if c=='\n' and the file is line buffered.
45  */
46 int
47 __swbuf(c, fp)
48 	register int c;
49 	register FILE *fp;
50 {
51 	register int n;
52 
53 	/*
54 	 * In case we cannot write, or longjmp takes us out early,
55 	 * make sure _w is 0 (if fully- or un-buffered) or -_bf._size
56 	 * (if line buffered) so that we will get called again.
57 	 * If we did not do this, a sufficient number of putc()
58 	 * calls might wrap _w from negative to positive.
59 	 */
60 	fp->_w = fp->_lbfsize;
61 	if (cantwrite(fp)) {
62 		errno = EBADF;
63 		return (EOF);
64 	}
65 	c = (unsigned char)c;
66 
67 	/*
68 	 * If it is completely full, flush it out.  Then, in any case,
69 	 * stuff c into the buffer.  If this causes the buffer to fill
70 	 * completely, or if c is '\n' and the file is line buffered,
71 	 * flush it (perhaps a second time).  The second flush will always
72 	 * happen on unbuffered streams, where _bf._size==1; fflush()
73 	 * guarantees that putc() will always call wbuf() by setting _w
74 	 * to 0, so we need not do anything else.
75 	 */
76 	n = fp->_p - fp->_bf._base;
77 	if (n >= fp->_bf._size) {
78 		if (fflush(fp))
79 			return (EOF);
80 		n = 0;
81 	}
82 	fp->_w--;
83 	*fp->_p++ = c;
84 	if (++n == fp->_bf._size || (fp->_flags & __SLBF && c == '\n'))
85 		if (fflush(fp))
86 			return (EOF);
87 	return (c);
88 }
89