1/*	$OpenBSD: refill.c,v 1.11 2009/11/09 00:18:27 kurt Exp $ */
2/*-
3 * Copyright (c) 1990, 1993
4 *	The Regents of the University of California.  All rights reserved.
5 *
6 * This code is derived from software contributed to Berkeley by
7 * Chris Torek.
8 *
9 * Redistribution and use in source and binary forms, with or without
10 * modification, are permitted provided that the following conditions
11 * are met:
12 * 1. Redistributions of source code must retain the above copyright
13 *    notice, this list of conditions and the following disclaimer.
14 * 2. Redistributions in binary form must reproduce the above copyright
15 *    notice, this list of conditions and the following disclaimer in the
16 *    documentation and/or other materials provided with the distribution.
17 * 3. Neither the name of the University nor the names of its contributors
18 *    may be used to endorse or promote products derived from this software
19 *    without specific prior written permission.
20 *
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
31 * SUCH DAMAGE.
32 */
33
34#include <errno.h>
35#include <stdio.h>
36#include <stdlib.h>
37#include "local.h"
38
39static int
40lflush(FILE *fp)
41{
42	if ((fp->_flags & (__SLBF|__SWR)) == (__SLBF|__SWR))
43		return (__sflush_locked(fp));	/* ignored... */
44	return (0);
45}
46
47/*
48 * Refill a stdio buffer.
49 * Return EOF on eof or error, 0 otherwise.
50 */
51int
52__srefill(FILE *fp)
53{
54	fp->_r = 0;		/* largely a convenience for callers */
55
56#if !defined(__ANDROID__)
57	/* SysV does not make this test; take it out for compatibility */
58	if (fp->_flags & __SEOF)
59		return (EOF);
60#endif
61
62	/* if not already reading, have to be reading and writing */
63	if ((fp->_flags & __SRD) == 0) {
64		if ((fp->_flags & __SRW) == 0) {
65			errno = EBADF;
66			fp->_flags |= __SERR;
67			return (EOF);
68		}
69		/* switch to reading */
70		if (fp->_flags & __SWR) {
71			if (__sflush(fp))
72				return (EOF);
73			fp->_flags &= ~__SWR;
74			fp->_w = 0;
75			fp->_lbfsize = 0;
76		}
77		fp->_flags |= __SRD;
78	} else {
79		/*
80		 * We were reading.  If there is an ungetc buffer,
81		 * we must have been reading from that.  Drop it,
82		 * restoring the previous buffer (if any).  If there
83		 * is anything in that buffer, return.
84		 */
85		if (HASUB(fp)) {
86			FREEUB(fp);
87			if ((fp->_r = fp->_ur) != 0) {
88				fp->_p = fp->_up;
89				return (0);
90			}
91		}
92	}
93
94	if (fp->_bf._base == NULL)
95		__smakebuf(fp);
96
97	/*
98	 * Before reading from a line buffered or unbuffered file,
99	 * flush all line buffered output files, per the ANSI C
100	 * standard.
101	 */
102	if (fp->_flags & (__SLBF|__SNBF)) {
103		/* Ignore this file in _fwalk to avoid potential deadlock. */
104		fp->_flags |= __SIGN;
105		(void) _fwalk(lflush);
106		fp->_flags &= ~__SIGN;
107
108		/* Now flush this file without locking it. */
109		if ((fp->_flags & (__SLBF|__SWR)) == (__SLBF|__SWR))
110			__sflush(fp);
111	}
112	fp->_p = fp->_bf._base;
113	fp->_r = (*fp->_read)(fp->_cookie, (char *)fp->_p, fp->_bf._size);
114	fp->_flags &= ~__SMOD;	/* buffer contents are again pristine */
115	if (fp->_r <= 0) {
116		if (fp->_r == 0)
117			fp->_flags |= __SEOF;
118		else {
119			fp->_r = 0;
120			fp->_flags |= __SERR;
121		}
122		return (EOF);
123	}
124	return (0);
125}
126