xref: /freebsd/lib/libc/stdio/refill.c (revision ef5d438ed4bc17ad7ece3e40fe4d1f9baf3aadf7)
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)
38 static 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 
46 static
47 lflush(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