refill.c revision 1574 
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. All advertising materials mentioning features or use of this software
17 *    must display the following acknowledgement:
18 *	This product includes software developed by the University of
19 *	California, Berkeley and its contributors.
20 * 4. Neither the name of the University nor the names of its contributors
21 *    may be used to endorse or promote products derived from this software
22 *    without specific prior written permission.
23 *
24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
27 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
34 * SUCH DAMAGE.
35 */
36
37#if defined(LIBC_SCCS) && !defined(lint)
38static char sccsid[] = "@(#)refill.c	8.1 (Berkeley) 6/4/93";
39#endif /* LIBC_SCCS and not lint */
40
41#include <errno.h>
42#include <stdio.h>
43#include <stdlib.h>
44#include "local.h"
45
46static
47lflush(fp)
48	FILE *fp;
49{
50
51	if ((fp->_flags & (__SLBF|__SWR)) == __SLBF|__SWR)
52		return (__sflush(fp));
53	return (0);
54}
55
56/*
57 * Refill a stdio buffer.
58 * Return EOF on eof or error, 0 otherwise.
59 */
60__srefill(fp)
61	register FILE *fp;
62{
63
64	/* make sure stdio is set up */
65	if (!__sdidinit)
66		__sinit();
67
68	fp->_r = 0;		/* largely a convenience for callers */
69
70	/* SysV does not make this test; take it out for compatibility */
71	if (fp->_flags & __SEOF)
72		return (EOF);
73
74	/* if not already reading, have to be reading and writing */
75	if ((fp->_flags & __SRD) == 0) {
76		if ((fp->_flags & __SRW) == 0) {
77			errno = EBADF;
78			return (EOF);
79		}
80		/* switch to reading */
81		if (fp->_flags & __SWR) {
82			if (__sflush(fp))
83				return (EOF);
84			fp->_flags &= ~__SWR;
85			fp->_w = 0;
86			fp->_lbfsize = 0;
87		}
88		fp->_flags |= __SRD;
89	} else {
90		/*
91		 * We were reading.  If there is an ungetc buffer,
92		 * we must have been reading from that.  Drop it,
93		 * restoring the previous buffer (if any).  If there
94		 * is anything in that buffer, return.
95		 */
96		if (HASUB(fp)) {
97			FREEUB(fp);
98			if ((fp->_r = fp->_ur) != 0) {
99				fp->_p = fp->_up;
100				return (0);
101			}
102		}
103	}
104
105	if (fp->_bf._base == NULL)
106		__smakebuf(fp);
107
108	/*
109	 * Before reading from a line buffered or unbuffered file,
110	 * flush all line buffered output files, per the ANSI C
111	 * standard.
112	 */
113	if (fp->_flags & (__SLBF|__SNBF))
114		(void) _fwalk(lflush);
115	fp->_p = fp->_bf._base;
116	fp->_r = (*fp->_read)(fp->_cookie, (char *)fp->_p, fp->_bf._size);
117	fp->_flags &= ~__SMOD;	/* buffer contents are again pristine */
118	if (fp->_r <= 0) {
119		if (fp->_r == 0)
120			fp->_flags |= __SEOF;
121		else {
122			fp->_r = 0;
123			fp->_flags |= __SERR;
124		}
125		return (EOF);
126	}
127	return (0);
128}
129