xref: /csrg-svn/lib/libc/stdio/wbuf.c (revision 46075)
1*46075Sbostic /*-
2*46075Sbostic  * Copyright (c) 1990 The Regents of the University of California.
3*46075Sbostic  * All rights reserved.
4*46075Sbostic  *
5*46075Sbostic  * This code is derived from software contributed to Berkeley by
6*46075Sbostic  * Chris Torek.
7*46075Sbostic  *
8*46075Sbostic  * %sccs.include.redist.c%
921403Sdist  */
1021403Sdist 
1126646Sdonn #if defined(LIBC_SCCS) && !defined(lint)
12*46075Sbostic static char sccsid[] = "@(#)wbuf.c	5.6 (Berkeley) 01/20/91";
13*46075Sbostic #endif /* LIBC_SCCS and not lint */
1421403Sdist 
15*46075Sbostic #include <stdio.h>
16*46075Sbostic #include "local.h"
172003Swnj 
18*46075Sbostic /*
19*46075Sbostic  * Write the given character into the (probably full) buffer for
20*46075Sbostic  * the given file.  Flush the buffer out if it is or becomes full,
21*46075Sbostic  * or if c=='\n' and the file is line buffered.
22*46075Sbostic  */
23*46075Sbostic __swbuf(c, fp)
24*46075Sbostic 	register int c;
25*46075Sbostic 	register FILE *fp;
262003Swnj {
27*46075Sbostic 	register int n;
282003Swnj 
29*46075Sbostic 	/*
30*46075Sbostic 	 * In case we cannot write, or longjmp takes us out early,
31*46075Sbostic 	 * make sure _w is 0 (if fully- or un-buffered) or -_bf._size
32*46075Sbostic 	 * (if line buffered) so that we will get called again.
33*46075Sbostic 	 * If we did not do this, a sufficient number of putc()
34*46075Sbostic 	 * calls might wrap _w from negative to positive.
35*46075Sbostic 	 */
36*46075Sbostic 	fp->_w = fp->_lbfsize;
37*46075Sbostic 	if (cantwrite(fp))
38*46075Sbostic 		return (EOF);
39*46075Sbostic 	c = (unsigned char)c;
403163Stoy 
41*46075Sbostic 	/*
42*46075Sbostic 	 * If it is completely full, flush it out.  Then, in any case,
43*46075Sbostic 	 * stuff c into the buffer.  If this causes the buffer to fill
44*46075Sbostic 	 * completely, or if c is '\n' and the file is line buffered,
45*46075Sbostic 	 * flush it (perhaps a second time).  The second flush will always
46*46075Sbostic 	 * happen on unbuffered streams, where _bf._size==1; fflush()
47*46075Sbostic 	 * guarantees that putc() will always call wbuf() by setting _w
48*46075Sbostic 	 * to 0, so we need not do anything else.
49*46075Sbostic 	 */
50*46075Sbostic 	n = fp->_p - fp->_bf._base;
51*46075Sbostic 	if (n >= fp->_bf._size) {
52*46075Sbostic 		if (fflush(fp))
53*46075Sbostic 			return (EOF);
54*46075Sbostic 		n = 0;
552003Swnj 	}
56*46075Sbostic 	fp->_w--;
57*46075Sbostic 	*fp->_p++ = c;
58*46075Sbostic 	if (++n == fp->_bf._size || (fp->_flags & __SLBF && c == '\n'))
59*46075Sbostic 		if (fflush(fp))
60*46075Sbostic 			return (EOF);
61*46075Sbostic 	return (c);
622003Swnj }
63