ungetc.c revision 1.10
1 /* $NetBSD: ungetc.c,v 1.10 1999/09/16 11:45:31 lukem Exp $ */ 2 3 /*- 4 * Copyright (c) 1990, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Chris Torek. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. All advertising materials mentioning features or use of this software 19 * must display the following acknowledgement: 20 * This product includes software developed by the University of 21 * California, Berkeley and its contributors. 22 * 4. Neither the name of the University nor the names of its contributors 23 * may be used to endorse or promote products derived from this software 24 * without specific prior written permission. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 27 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 28 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 29 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 30 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 31 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 32 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 33 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 34 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 35 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 36 * SUCH DAMAGE. 37 */ 38 39 #include <sys/cdefs.h> 40 #if defined(LIBC_SCCS) && !defined(lint) 41 #if 0 42 static char sccsid[] = "@(#)ungetc.c 8.2 (Berkeley) 11/3/93"; 43 #else 44 __RCSID("$NetBSD: ungetc.c,v 1.10 1999/09/16 11:45:31 lukem Exp $"); 45 #endif 46 #endif /* LIBC_SCCS and not lint */ 47 48 #include <assert.h> 49 #include <errno.h> 50 #include <stdio.h> 51 #include <stdlib.h> 52 #include <string.h> 53 #include "local.h" 54 #include "reentrant.h" 55 56 static int __submore __P((FILE *)); 57 /* 58 * Expand the ungetc buffer `in place'. That is, adjust fp->_p when 59 * the buffer moves, so that it points the same distance from the end, 60 * and move the bytes in the buffer around as necessary so that they 61 * are all at the end (stack-style). 62 */ 63 static int 64 __submore(fp) 65 FILE *fp; 66 { 67 int i; 68 unsigned char *p; 69 70 _DIAGASSERT(fp != NULL); 71 72 if (fp->_ub._base == fp->_ubuf) { 73 /* 74 * Get a new buffer (rather than expanding the old one). 75 */ 76 if ((p = malloc((size_t)BUFSIZ)) == NULL) 77 return (EOF); 78 fp->_ub._base = p; 79 fp->_ub._size = BUFSIZ; 80 p += BUFSIZ - sizeof(fp->_ubuf); 81 for (i = sizeof(fp->_ubuf); --i >= 0;) 82 p[i] = fp->_ubuf[i]; 83 fp->_p = p; 84 return (0); 85 } 86 i = fp->_ub._size; 87 p = realloc(fp->_ub._base, (size_t)(i << 1)); 88 if (p == NULL) 89 return (EOF); 90 /* no overlap (hence can use memcpy) because we doubled the size */ 91 (void)memcpy((void *)(p + i), (void *)p, (size_t)i); 92 fp->_p = p + i; 93 fp->_ub._base = p; 94 fp->_ub._size = i << 1; 95 return (0); 96 } 97 98 int 99 ungetc(c, fp) 100 int c; 101 FILE *fp; 102 { 103 104 _DIAGASSERT(fp != NULL); 105 #ifdef _DIAGNOSTIC 106 if (fp == NULL) { 107 errno = EBADF; 108 return (EOF); 109 } 110 #endif 111 112 if (c == EOF) 113 return (EOF); 114 if (!__sdidinit) 115 __sinit(); 116 FLOCKFILE(fp); 117 if ((fp->_flags & __SRD) == 0) { 118 /* 119 * Not already reading: no good unless reading-and-writing. 120 * Otherwise, flush any current write stuff. 121 */ 122 if ((fp->_flags & __SRW) == 0) { 123 FUNLOCKFILE(fp); 124 return (EOF); 125 } 126 if (fp->_flags & __SWR) { 127 if (__sflush(fp)) { 128 FUNLOCKFILE(fp); 129 return (EOF); 130 } 131 fp->_flags &= ~__SWR; 132 fp->_w = 0; 133 fp->_lbfsize = 0; 134 } 135 fp->_flags |= __SRD; 136 } 137 c = (unsigned char)c; 138 139 /* 140 * If we are in the middle of ungetc'ing, just continue. 141 * This may require expanding the current ungetc buffer. 142 */ 143 if (HASUB(fp)) { 144 if (fp->_r >= fp->_ub._size && __submore(fp)) { 145 FUNLOCKFILE(fp); 146 return (EOF); 147 } 148 *--fp->_p = c; 149 fp->_r++; 150 FUNLOCKFILE(fp); 151 return (c); 152 } 153 fp->_flags &= ~__SEOF; 154 155 /* 156 * If we can handle this by simply backing up, do so, 157 * but never replace the original character. 158 * (This makes sscanf() work when scanning `const' data.) 159 */ 160 if (fp->_bf._base != NULL && fp->_p > fp->_bf._base && 161 fp->_p[-1] == c) { 162 fp->_p--; 163 fp->_r++; 164 FUNLOCKFILE(fp); 165 return (c); 166 } 167 168 /* 169 * Create an ungetc buffer. 170 * Initially, we will use the `reserve' buffer. 171 */ 172 fp->_ur = fp->_r; 173 fp->_up = fp->_p; 174 fp->_ub._base = fp->_ubuf; 175 fp->_ub._size = sizeof(fp->_ubuf); 176 fp->_ubuf[sizeof(fp->_ubuf) - 1] = c; 177 fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1]; 178 fp->_r = 1; 179 FUNLOCKFILE(fp); 180 return (c); 181 } 182
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