xref: /illumos-gate/usr/src/lib/libc/port/stdio/_filbuf.c (revision 78a2e113edb6fe0a0382b403b55d92e8f0bba78f)
1 /*
2  * CDDL HEADER START
3  *
4  * The contents of this file are subject to the terms of the
5  * Common Development and Distribution License (the "License").
6  * You may not use this file except in compliance with the License.
7  *
8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9  * or http://www.opensolaris.org/os/licensing.
10  * See the License for the specific language governing permissions
11  * and limitations under the License.
12  *
13  * When distributing Covered Code, include this CDDL HEADER in each
14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15  * If applicable, add the following below this CDDL HEADER, with the
16  * fields enclosed by brackets "[]" replaced with your own identifying
17  * information: Portions Copyright [yyyy] [name of copyright owner]
18  *
19  * CDDL HEADER END
20  */
21 
22 /*
23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
24  * Use is subject to license terms.
25  */
26 
27 /*	Copyright (c) 1988 AT&T	*/
28 /*	  All Rights Reserved  	*/
29 
30 #pragma ident	"%Z%%M%	%I%	%E% SMI"
31 
32 
33 #pragma weak __filbuf = _filbuf
34 
35 #include "lint.h"
36 #include "file64.h"
37 #include <stdio.h>
38 #include <errno.h>
39 #include <sys/types.h>
40 #include <unistd.h>
41 #include "stdiom.h"
42 
43 
44 static int
45 _xpg4_check(void)
46 {
47 	extern int	__xpg4;
48 
49 	return (__xpg4);
50 }
51 
52 /* fill buffer, return first character or EOF */
53 int
54 _filbuf(FILE *iop)
55 {
56 	ssize_t res;
57 	size_t nbyte;
58 	Uchar *endbuf;
59 #ifdef	_LP64
60 	unsigned int	flag;
61 #else
62 	unsigned char	flag;
63 #endif
64 
65 	if (!(iop->_flag & _IOREAD))	/* check, correct permissions */
66 	{
67 		if (iop->_flag & _IORW)
68 			iop->_flag |= _IOREAD; /* change direction */
69 						/* to read - fseek */
70 		else {
71 			errno = EBADF;
72 			return (EOF);
73 		}
74 	}
75 
76 	if (iop->_base == 0) {
77 		if ((endbuf = _findbuf(iop)) == 0) /* get buffer and */
78 						/* end_of_buffer */
79 			return (EOF);
80 	}
81 	else
82 		endbuf = _bufend(iop);
83 
84 	/*
85 	 * Flush all line-buffered streams before we
86 	 * read no-buffered or line-buffered input.
87 	 */
88 	if (iop->_flag & (_IONBF | _IOLBF))
89 		_flushlbf();
90 	/*
91 	 * Changed the get family fns in Solaris 10 to comply with the
92 	 * 1990 C Standard and standards based upon it.  If the
93 	 * end-of-file indicator for the stream is set, or if the stream
94 	 * is at end-of-file, the function will return EOF, and the file
95 	 * position indicator for the stream will not be advanced.
96 	 * Additional bytes appended to the file do not clear the EOF
97 	 * indicator.
98 	 */
99 	if ((flag = iop->_flag) & _IOEOF) {
100 		if (_xpg4_check()) {
101 			/*
102 			 * A previous read() has returned 0 (below),
103 			 * therefore iop->_cnt was set to 0, and the EOF
104 			 * indicator was set before returning EOF.  Reset
105 			 * iop->_cnt to 0; it has likely been changed by
106 			 * a function such as getc().
107 			 */
108 			iop->_cnt = 0;
109 			return (EOF);
110 		}
111 	}
112 	/*
113 	 * Fill buffer or read 1 byte for unbuffered, handling any errors.
114 	 */
115 	iop->_ptr = iop->_base;
116 	if (flag & _IONBF)
117 		nbyte = 1;
118 	else
119 		nbyte = endbuf - iop->_base;
120 	if ((res = read(GET_FD(iop), (char *)iop->_base, nbyte)) > 0) {
121 		iop->_cnt = res - 1;
122 		return (*iop->_ptr++);
123 	}
124 
125 	iop->_cnt = 0;
126 	if (res == 0)
127 		iop->_flag |= _IOEOF;
128 	else if (!cancel_active())
129 		iop->_flag |= _IOERR;
130 	return (EOF);
131 }
132