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 * 4. Neither the name of the University nor the names of its contributors 17 * may be used to endorse or promote products derived from this software 18 * without specific prior written permission. 19 * 20 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 21 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 22 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 23 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 24 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 25 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 26 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 27 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 28 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 29 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 30 * SUCH DAMAGE. 31 * 32 * @(#)ungetc.c 8.2 (Berkeley) 11/3/93 33 * $FreeBSD: src/lib/libc/stdio/ungetc.c,v 1.18 2008/04/17 22:17:54 jhb Exp $ 34 * $DragonFly: src/lib/libc/stdio/ungetc.c,v 1.8 2005/11/20 11:07:30 swildner Exp $ 35 */ 36 37 #include "namespace.h" 38 #include <stdio.h> 39 #include <stdlib.h> 40 #include <string.h> 41 #include "un-namespace.h" 42 #include "local.h" 43 #include "libc_private.h" 44 #include "priv_stdio.h" 45 46 static int __submore(FILE *); 47 48 /* 49 * Expand the ungetc buffer `in place'. That is, adjust fp->pub._p when 50 * the buffer moves, so that it points the same distance from the end, 51 * and move the bytes in the buffer around as necessary so that they 52 * are all at the end (stack-style). 53 */ 54 static int 55 __submore(FILE *fp) 56 { 57 int i; 58 unsigned char *p; 59 60 if (fp->_ub._base == fp->_ubuf) { 61 /* 62 * Get a new buffer (rather than expanding the old one). 63 */ 64 if ((p = malloc((size_t)BUFSIZ)) == NULL) 65 return (EOF); 66 fp->_ub._base = p; 67 fp->_ub._size = BUFSIZ; 68 p += BUFSIZ - sizeof(fp->_ubuf); 69 for (i = sizeof(fp->_ubuf); --i >= 0;) 70 p[i] = fp->_ubuf[i]; 71 fp->pub._p = p; 72 return (0); 73 } 74 i = fp->_ub._size; 75 p = realloc(fp->_ub._base, (size_t)(i << 1)); 76 if (p == NULL) 77 return (EOF); 78 /* no overlap (hence can use memcpy) because we doubled the size */ 79 memcpy((void *)(p + i), (void *)p, (size_t)i); 80 fp->pub._p = p + i; 81 fp->_ub._base = p; 82 fp->_ub._size = i << 1; 83 return (0); 84 } 85 86 /* 87 * MT-safe version 88 */ 89 int 90 ungetc(int c, FILE *fp) 91 { 92 int ret; 93 94 if (!__sdidinit) 95 __sinit(); 96 FLOCKFILE(fp); 97 ORIENT(fp, -1); 98 ret = __ungetc(c, fp); 99 FUNLOCKFILE(fp); 100 return (ret); 101 } 102 103 /* 104 * Non-MT-safe version 105 */ 106 int 107 __ungetc(int c, FILE *fp) 108 { 109 if (c == EOF) 110 return (EOF); 111 if ((fp->pub._flags & __SRD) == 0) { 112 /* 113 * Not already reading: no good unless reading-and-writing. 114 * Otherwise, flush any current write stuff. 115 */ 116 if ((fp->pub._flags & __SRW) == 0) 117 return (EOF); 118 if (fp->pub._flags & __SWR) { 119 if (__sflush(fp)) 120 return (EOF); 121 fp->pub._flags &= ~__SWR; 122 fp->pub._w = 0; 123 fp->pub._lbfsize = 0; 124 } 125 fp->pub._flags |= __SRD; 126 } 127 c = (unsigned char)c; 128 129 /* 130 * If we are in the middle of ungetc'ing, just continue. 131 * This may require expanding the current ungetc buffer. 132 */ 133 if (HASUB(fp)) { 134 if (fp->pub._r >= fp->_ub._size && __submore(fp)) 135 return (EOF); 136 *--fp->pub._p = c; 137 fp->pub._r++; 138 return (c); 139 } 140 fp->pub._flags &= ~__SEOF; 141 142 /* 143 * If we can handle this by simply backing up, do so, 144 * but never replace the original character. 145 * (This makes sscanf() work when scanning `const' data.) 146 */ 147 if (fp->_bf._base != NULL && fp->pub._p > fp->_bf._base && 148 fp->pub._p[-1] == c) { 149 fp->pub._p--; 150 fp->pub._r++; 151 return (c); 152 } 153 154 /* 155 * Create an ungetc buffer. 156 * Initially, we will use the `reserve' buffer. 157 */ 158 fp->_ur = fp->pub._r; 159 fp->_up = fp->pub._p; 160 fp->_ub._base = fp->_ubuf; 161 fp->_ub._size = sizeof(fp->_ubuf); 162 fp->_ubuf[sizeof(fp->_ubuf) - 1] = c; 163 fp->pub._p = &fp->_ubuf[sizeof(fp->_ubuf) - 1]; 164 fp->pub._r = 1; 165 return (c); 166 } 167