xref: /freebsd/lib/libc/stdio/refill.c (revision 641a6cfb86023499caafe26a4d821a0b885cf00b)
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  * 4. 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 sccsid[] = "@(#)refill.c	8.1 (Berkeley) 6/4/93";
35 #endif /* LIBC_SCCS and not lint */
36 #include <sys/cdefs.h>
37 __FBSDID("$FreeBSD$");
38 
39 #include "namespace.h"
40 #include <errno.h>
41 #include <stdio.h>
42 #include <stdlib.h>
43 #include "un-namespace.h"
44 
45 #include "libc_private.h"
46 #include "local.h"
47 
48 static int lflush(FILE *);
49 
50 static int
51 lflush(FILE *fp)
52 {
53 	int	ret = 0;
54 
55 	if ((fp->_flags & (__SLBF|__SWR)) == (__SLBF|__SWR)) {
56 		FLOCKFILE(fp);
57 		ret = __sflush(fp);
58 		FUNLOCKFILE(fp);
59 	}
60 	return (ret);
61 }
62 
63 /*
64  * Refill a stdio buffer.
65  * Return EOF on eof or error, 0 otherwise.
66  */
67 int
68 __srefill(FILE *fp)
69 {
70 
71 	/* make sure stdio is set up */
72 	if (!__sdidinit)
73 		__sinit();
74 
75 	ORIENT(fp, -1);
76 
77 	fp->_r = 0;		/* largely a convenience for callers */
78 
79 	/* SysV does not make this test; take it out for compatibility */
80 	if (fp->_flags & __SEOF)
81 		return (EOF);
82 
83 	/* if not already reading, have to be reading and writing */
84 	if ((fp->_flags & __SRD) == 0) {
85 		if ((fp->_flags & __SRW) == 0) {
86 			errno = EBADF;
87 			fp->_flags |= __SERR;
88 			return (EOF);
89 		}
90 		/* switch to reading */
91 		if (fp->_flags & __SWR) {
92 			if (__sflush(fp))
93 				return (EOF);
94 			fp->_flags &= ~__SWR;
95 			fp->_w = 0;
96 			fp->_lbfsize = 0;
97 		}
98 		fp->_flags |= __SRD;
99 	} else {
100 		/*
101 		 * We were reading.  If there is an ungetc buffer,
102 		 * we must have been reading from that.  Drop it,
103 		 * restoring the previous buffer (if any).  If there
104 		 * is anything in that buffer, return.
105 		 */
106 		if (HASUB(fp)) {
107 			FREEUB(fp);
108 			if ((fp->_r = fp->_ur) != 0) {
109 				fp->_p = fp->_up;
110 				return (0);
111 			}
112 		}
113 	}
114 
115 	if (fp->_bf._base == NULL)
116 		__smakebuf(fp);
117 
118 	/*
119 	 * Before reading from a line buffered or unbuffered file,
120 	 * flush all line buffered output files, per the ANSI C
121 	 * standard.
122 	 */
123 	if (fp->_flags & (__SLBF|__SNBF)) {
124 		/* Ignore this file in _fwalk to avoid potential deadlock. */
125 		fp->_flags |= __SIGN;
126 		(void) _fwalk(lflush);
127 		fp->_flags &= ~__SIGN;
128 
129 		/* Now flush this file without locking it. */
130 		if ((fp->_flags & (__SLBF|__SWR)) == (__SLBF|__SWR))
131 			__sflush(fp);
132 	}
133 	fp->_p = fp->_bf._base;
134 	fp->_r = _sread(fp, (char *)fp->_p, fp->_bf._size);
135 	fp->_flags &= ~__SMOD;	/* buffer contents are again pristine */
136 	if (fp->_r <= 0) {
137 		if (fp->_r == 0)
138 			fp->_flags |= __SEOF;
139 		else {
140 			fp->_r = 0;
141 			fp->_flags |= __SERR;
142 		}
143 		return (EOF);
144 	}
145 	return (0);
146 }
147