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wbuf.c revision 1.6 
      1 /*	$NetBSD: wbuf.c,v 1.6 1997/05/03 09:01:52 kleink Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 1990, 1993
      5  *	The Regents of the University of California.  All rights reserved.
      6  *
      7  * This code is derived from software contributed to Berkeley by
      8  * Chris Torek.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  * 3. All advertising materials mentioning features or use of this software
     19  *    must display the following acknowledgement:
     20  *	This product includes software developed by the University of
     21  *	California, Berkeley and its contributors.
     22  * 4. Neither the name of the University nor the names of its contributors
     23  *    may be used to endorse or promote products derived from this software
     24  *    without specific prior written permission.
     25  *
     26  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     27  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     28  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     29  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     30  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     31  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     32  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     33  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     34  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     35  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     36  * SUCH DAMAGE.
     37  */
     38 
     39 #if defined(LIBC_SCCS) && !defined(lint)
     40 #if 0
     41 static char sccsid[] = "@(#)wbuf.c	8.1 (Berkeley) 6/4/93";
     42 #endif
     43 static char rcsid[] = "$NetBSD: wbuf.c,v 1.6 1997/05/03 09:01:52 kleink Exp $";
     44 #endif /* LIBC_SCCS and not lint */
     45 
     46 #include <errno.h>
     47 #include <stdio.h>
     48 #include "local.h"
     49 
     50 /*
     51  * Write the given character into the (probably full) buffer for
     52  * the given file.  Flush the buffer out if it is or becomes full,
     53  * or if c=='\n' and the file is line buffered.
     54  */
     55 int
     56 __swbuf(c, fp)
     57 	register int c;
     58 	register FILE *fp;
     59 {
     60 	register int n;
     61 
     62 	/*
     63 	 * In case we cannot write, or longjmp takes us out early,
     64 	 * make sure _w is 0 (if fully- or un-buffered) or -_bf._size
     65 	 * (if line buffered) so that we will get called again.
     66 	 * If we did not do this, a sufficient number of putc()
     67 	 * calls might wrap _w from negative to positive.
     68 	 */
     69 	fp->_w = fp->_lbfsize;
     70 	if (cantwrite(fp)) {
     71 		errno = EBADF;
     72 		return (EOF);
     73 	}
     74 	c = (unsigned char)c;
     75 
     76 	/*
     77 	 * If it is completely full, flush it out.  Then, in any case,
     78 	 * stuff c into the buffer.  If this causes the buffer to fill
     79 	 * completely, or if c is '\n' and the file is line buffered,
     80 	 * flush it (perhaps a second time).  The second flush will always
     81 	 * happen on unbuffered streams, where _bf._size==1; fflush()
     82 	 * guarantees that putc() will always call wbuf() by setting _w
     83 	 * to 0, so we need not do anything else.
     84 	 */
     85 	n = fp->_p - fp->_bf._base;
     86 	if (n >= fp->_bf._size) {
     87 		if (fflush(fp))
     88 			return (EOF);
     89 		n = 0;
     90 	}
     91 	fp->_w--;
     92 	*fp->_p++ = c;
     93 	if (++n == fp->_bf._size || (fp->_flags & __SLBF && c == '\n'))
     94 		if (fflush(fp))
     95 			return (EOF);
     96 	return (c);
     97 }
     98