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 1.5 2005/05/09 12:43:40 davidxu 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 #include "local.h" 47 #include "libc_private.h" 48 49 static int __submore (FILE *); 50 51 /* 52 * Expand the ungetc buffer `in place'. That is, adjust fp->_p when 53 * the buffer moves, so that it points the same distance from the end, 54 * and move the bytes in the buffer around as necessary so that they 55 * are all at the end (stack-style). 56 */ 57 static int 58 __submore(FILE *fp) 59 { 60 int i; 61 unsigned char *p; 62 63 if (fp->_ub._base == fp->_ubuf) { 64 /* 65 * Get a new buffer (rather than expanding the old one). 66 */ 67 if ((p = malloc((size_t)BUFSIZ)) == NULL) 68 return (EOF); 69 fp->_ub._base = p; 70 fp->_ub._size = BUFSIZ; 71 p += BUFSIZ - sizeof(fp->_ubuf); 72 for (i = sizeof(fp->_ubuf); --i >= 0;) 73 p[i] = fp->_ubuf[i]; 74 fp->_p = p; 75 return (0); 76 } 77 i = fp->_ub._size; 78 p = realloc(fp->_ub._base, (size_t)(i << 1)); 79 if (p == NULL) 80 return (EOF); 81 /* no overlap (hence can use memcpy) because we doubled the size */ 82 (void)memcpy((void *)(p + i), (void *)p, (size_t)i); 83 fp->_p = p + i; 84 fp->_ub._base = p; 85 fp->_ub._size = i << 1; 86 return (0); 87 } 88 89 /* 90 * MT-safe version 91 */ 92 int 93 ungetc(int c, FILE *fp) 94 { 95 int ret; 96 97 if (c == EOF) 98 return (EOF); 99 if (!__sdidinit) 100 __sinit(); 101 FLOCKFILE(fp); 102 ret = __ungetc(c, fp); 103 FUNLOCKFILE(fp); 104 return(ret); 105 } 106 107 /* 108 * Non-MT-safe version 109 */ 110 int 111 __ungetc(int c, FILE *fp) 112 { 113 if (c == EOF) 114 return(EOF); 115 if ((fp->_flags & __SRD) == 0) { 116 /* 117 * Not already reading: no good unless reading-and-writing. 118 * Otherwise, flush any current write stuff. 119 */ 120 if ((fp->_flags & __SRW) == 0) { 121 return (EOF); 122 } 123 if (fp->_flags & __SWR) { 124 if (__sflush(fp)) { 125 return (EOF); 126 } 127 fp->_flags &= ~__SWR; 128 fp->_w = 0; 129 fp->_lbfsize = 0; 130 } 131 fp->_flags |= __SRD; 132 } 133 c = (unsigned char)c; 134 135 /* 136 * If we are in the middle of ungetc'ing, just continue. 137 * This may require expanding the current ungetc buffer. 138 */ 139 if (HASUB(fp)) { 140 if (fp->_r >= fp->_ub._size && __submore(fp)) { 141 return (EOF); 142 } 143 *--fp->_p = c; 144 fp->_r++; 145 return (c); 146 } 147 fp->_flags &= ~__SEOF; 148 149 /* 150 * If we can handle this by simply backing up, do so, 151 * but never replace the original character. 152 * (This makes sscanf() work when scanning `const' data.) 153 */ 154 if (fp->_bf._base != NULL && fp->_p > fp->_bf._base && 155 fp->_p[-1] == c) { 156 fp->_p--; 157 fp->_r++; 158 return (c); 159 } 160 161 /* 162 * Create an ungetc buffer. 163 * Initially, we will use the `reserve' buffer. 164 */ 165 fp->_ur = fp->_r; 166 fp->_extra->_up = fp->_p; 167 fp->_ub._base = fp->_ubuf; 168 fp->_ub._size = sizeof(fp->_ubuf); 169 fp->_ubuf[sizeof(fp->_ubuf) - 1] = c; 170 fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1]; 171 fp->_r = 1; 172 return (c); 173 } 174