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 * @(#)ungetc.c 8.2 (Berkeley) 11/3/93 37 * $FreeBSD: src/lib/libc/stdio/ungetc.c,v 1.7.2.1 2001/03/05 11:27:49 obrien Exp $ 38 * $DragonFly: src/lib/libc/stdio/ungetc.c,v 1.8 2005/11/20 11:07:30 swildner Exp $ 39 */ 40 41 #include "namespace.h" 42 #include <stdio.h> 43 #include <stdlib.h> 44 #include <string.h> 45 #include "un-namespace.h" 46 47 #include "local.h" 48 #include "libc_private.h" 49 #include "priv_stdio.h" 50 51 static int __submore (FILE *); 52 53 /* 54 * Expand the ungetc buffer `in place'. That is, adjust fp->_p when 55 * the buffer moves, so that it points the same distance from the end, 56 * and move the bytes in the buffer around as necessary so that they 57 * are all at the end (stack-style). 58 */ 59 static int 60 __submore(FILE *fp) 61 { 62 int i; 63 unsigned char *p; 64 65 if (fp->_ub._base == fp->_ubuf) { 66 /* 67 * Get a new buffer (rather than expanding the old one). 68 */ 69 if ((p = malloc((size_t)BUFSIZ)) == NULL) 70 return (EOF); 71 fp->_ub._base = p; 72 fp->_ub._size = BUFSIZ; 73 p += BUFSIZ - sizeof(fp->_ubuf); 74 for (i = sizeof(fp->_ubuf); --i >= 0;) 75 p[i] = fp->_ubuf[i]; 76 fp->pub._p = p; 77 return (0); 78 } 79 i = fp->_ub._size; 80 p = realloc(fp->_ub._base, (size_t)(i << 1)); 81 if (p == NULL) 82 return (EOF); 83 /* no overlap (hence can use memcpy) because we doubled the size */ 84 memcpy((void *)(p + i), (void *)p, (size_t)i); 85 fp->pub._p = p + i; 86 fp->_ub._base = p; 87 fp->_ub._size = i << 1; 88 return (0); 89 } 90 91 /* 92 * MT-safe version 93 */ 94 int 95 ungetc(int c, FILE *fp) 96 { 97 int ret; 98 99 if (c == EOF) 100 return (EOF); 101 if (!__sdidinit) 102 __sinit(); 103 FLOCKFILE(fp); 104 ret = __ungetc(c, fp); 105 FUNLOCKFILE(fp); 106 return(ret); 107 } 108 109 /* 110 * Non-MT-safe version 111 */ 112 int 113 __ungetc(int c, FILE *fp) 114 { 115 if (c == EOF) 116 return(EOF); 117 if ((fp->pub._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->pub._flags & __SRW) == 0) { 123 return (EOF); 124 } 125 if (fp->pub._flags & __SWR) { 126 if (__sflush(fp)) { 127 return (EOF); 128 } 129 fp->pub._flags &= ~__SWR; 130 fp->pub._w = 0; 131 fp->pub._lbfsize = 0; 132 } 133 fp->pub._flags |= __SRD; 134 } 135 c = (unsigned char)c; 136 137 /* 138 * If we are in the middle of ungetc'ing, just continue. 139 * This may require expanding the current ungetc buffer. 140 */ 141 if (HASUB(fp)) { 142 if (fp->pub._r >= fp->_ub._size && __submore(fp)) { 143 return (EOF); 144 } 145 *--fp->pub._p = c; 146 fp->pub._r++; 147 return (c); 148 } 149 fp->pub._flags &= ~__SEOF; 150 151 /* 152 * If we can handle this by simply backing up, do so, 153 * but never replace the original character. 154 * (This makes sscanf() work when scanning `const' data.) 155 */ 156 if (fp->_bf._base != NULL && fp->pub._p > fp->_bf._base && 157 fp->pub._p[-1] == c) { 158 fp->pub._p--; 159 fp->pub._r++; 160 return (c); 161 } 162 163 /* 164 * Create an ungetc buffer. 165 * Initially, we will use the `reserve' buffer. 166 */ 167 fp->_ur = fp->pub._r; 168 fp->_up = fp->pub._p; 169 fp->_ub._base = fp->_ubuf; 170 fp->_ub._size = sizeof(fp->_ubuf); 171 fp->_ubuf[sizeof(fp->_ubuf) - 1] = c; 172 fp->pub._p = &fp->_ubuf[sizeof(fp->_ubuf) - 1]; 173 fp->pub._r = 1; 174 return (c); 175 } 176