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. 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 */ 35 36 #include "namespace.h" 37 #include <stdio.h> 38 #include <stdlib.h> 39 #include <string.h> 40 #include "un-namespace.h" 41 #include "local.h" 42 #include "libc_private.h" 43 44 static int __submore(FILE *); 45 46 /* 47 * Expand the ungetc buffer `in place'. That is, adjust fp->pub._p when 48 * the buffer moves, so that it points the same distance from the end, 49 * and move the bytes in the buffer around as necessary so that they 50 * are all at the end (stack-style). 51 */ 52 static int 53 __submore(FILE *fp) 54 { 55 int i; 56 unsigned char *p; 57 58 if (fp->_ub._base == fp->_ubuf) { 59 /* 60 * Get a new buffer (rather than expanding the old one). 61 */ 62 if ((p = malloc((size_t)BUFSIZ)) == NULL) 63 return (EOF); 64 fp->_ub._base = p; 65 fp->_ub._size = BUFSIZ; 66 p += BUFSIZ - sizeof(fp->_ubuf); 67 for (i = sizeof(fp->_ubuf); --i >= 0;) 68 p[i] = fp->_ubuf[i]; 69 fp->pub._p = p; 70 return (0); 71 } 72 i = fp->_ub._size; 73 p = realloc(fp->_ub._base, (size_t)(i << 1)); 74 if (p == NULL) 75 return (EOF); 76 /* no overlap (hence can use memcpy) because we doubled the size */ 77 memcpy((void *)(p + i), (void *)p, (size_t)i); 78 fp->pub._p = p + i; 79 fp->_ub._base = p; 80 fp->_ub._size = i << 1; 81 return (0); 82 } 83 84 /* 85 * MT-safe version 86 */ 87 int 88 ungetc(int c, FILE *fp) 89 { 90 int ret; 91 92 if (!__sdidinit) 93 __sinit(); 94 FLOCKFILE(fp); 95 ORIENT(fp, -1); 96 ret = __ungetc(c, fp); 97 FUNLOCKFILE(fp); 98 return (ret); 99 } 100 101 /* 102 * Non-MT-safe version 103 */ 104 int 105 __ungetc(int c, FILE *fp) 106 { 107 if (c == EOF) 108 return (EOF); 109 if ((fp->pub._flags & __SRD) == 0) { 110 /* 111 * Not already reading: no good unless reading-and-writing. 112 * Otherwise, flush any current write stuff. 113 */ 114 if ((fp->pub._flags & __SRW) == 0) 115 return (EOF); 116 if (fp->pub._flags & __SWR) { 117 if (__sflush(fp)) 118 return (EOF); 119 fp->pub._flags &= ~__SWR; 120 fp->pub._w = 0; 121 fp->pub._lbfsize = 0; 122 } 123 fp->pub._flags |= __SRD; 124 } 125 c = (unsigned char)c; 126 127 /* 128 * If we are in the middle of ungetc'ing, just continue. 129 * This may require expanding the current ungetc buffer. 130 */ 131 if (HASUB(fp)) { 132 if (fp->pub._r >= fp->_ub._size && __submore(fp)) 133 return (EOF); 134 *--fp->pub._p = c; 135 fp->pub._r++; 136 return (c); 137 } 138 fp->pub._flags &= ~__SEOF; 139 140 /* 141 * If we can handle this by simply backing up, do so, 142 * but never replace the original character. 143 * (This makes sscanf() work when scanning `const' data.) 144 */ 145 if (fp->_bf._base != NULL && fp->pub._p > fp->_bf._base && 146 fp->pub._p[-1] == c) { 147 fp->pub._p--; 148 fp->pub._r++; 149 return (c); 150 } 151 152 /* 153 * Create an ungetc buffer. 154 * Initially, we will use the `reserve' buffer. 155 */ 156 fp->_ur = fp->pub._r; 157 fp->_up = fp->pub._p; 158 fp->_ub._base = fp->_ubuf; 159 fp->_ub._size = sizeof(fp->_ubuf); 160 fp->_ubuf[sizeof(fp->_ubuf) - 1] = c; 161 fp->pub._p = &fp->_ubuf[sizeof(fp->_ubuf) - 1]; 162 fp->pub._r = 1; 163 return (c); 164 } 165