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 1.3 2003/11/12 20:21:25 eirikn Exp $ 39 */ 40 41 #include <stdio.h> 42 #include <stdlib.h> 43 #include <string.h> 44 #include "local.h" 45 #include "libc_private.h" 46 47 static int __submore (FILE *); 48 49 /* 50 * Expand the ungetc buffer `in place'. That is, adjust fp->_p when 51 * the buffer moves, so that it points the same distance from the end, 52 * and move the bytes in the buffer around as necessary so that they 53 * are all at the end (stack-style). 54 */ 55 static int 56 __submore(FILE *fp) 57 { 58 int i; 59 unsigned char *p; 60 61 if (fp->_ub._base == fp->_ubuf) { 62 /* 63 * Get a new buffer (rather than expanding the old one). 64 */ 65 if ((p = malloc((size_t)BUFSIZ)) == NULL) 66 return (EOF); 67 fp->_ub._base = p; 68 fp->_ub._size = BUFSIZ; 69 p += BUFSIZ - sizeof(fp->_ubuf); 70 for (i = sizeof(fp->_ubuf); --i >= 0;) 71 p[i] = fp->_ubuf[i]; 72 fp->_p = p; 73 return (0); 74 } 75 i = fp->_ub._size; 76 p = realloc(fp->_ub._base, (size_t)(i << 1)); 77 if (p == NULL) 78 return (EOF); 79 /* no overlap (hence can use memcpy) because we doubled the size */ 80 (void)memcpy((void *)(p + i), (void *)p, (size_t)i); 81 fp->_p = p + i; 82 fp->_ub._base = p; 83 fp->_ub._size = i << 1; 84 return (0); 85 } 86 87 int 88 ungetc(int c, FILE *fp) 89 { 90 if (c == EOF) 91 return (EOF); 92 if (!__sdidinit) 93 __sinit(); 94 FLOCKFILE(fp); 95 if ((fp->_flags & __SRD) == 0) { 96 /* 97 * Not already reading: no good unless reading-and-writing. 98 * Otherwise, flush any current write stuff. 99 */ 100 if ((fp->_flags & __SRW) == 0) { 101 FUNLOCKFILE(fp); 102 return (EOF); 103 } 104 if (fp->_flags & __SWR) { 105 if (__sflush(fp)) { 106 FUNLOCKFILE(fp); 107 return (EOF); 108 } 109 fp->_flags &= ~__SWR; 110 fp->_w = 0; 111 fp->_lbfsize = 0; 112 } 113 fp->_flags |= __SRD; 114 } 115 c = (unsigned char)c; 116 117 /* 118 * If we are in the middle of ungetc'ing, just continue. 119 * This may require expanding the current ungetc buffer. 120 */ 121 if (HASUB(fp)) { 122 if (fp->_r >= fp->_ub._size && __submore(fp)) { 123 FUNLOCKFILE(fp); 124 return (EOF); 125 } 126 *--fp->_p = c; 127 fp->_r++; 128 FUNLOCKFILE(fp); 129 return (c); 130 } 131 fp->_flags &= ~__SEOF; 132 133 /* 134 * If we can handle this by simply backing up, do so, 135 * but never replace the original character. 136 * (This makes sscanf() work when scanning `const' data.) 137 */ 138 if (fp->_bf._base != NULL && fp->_p > fp->_bf._base && 139 fp->_p[-1] == c) { 140 fp->_p--; 141 fp->_r++; 142 FUNLOCKFILE(fp); 143 return (c); 144 } 145 146 /* 147 * Create an ungetc buffer. 148 * Initially, we will use the `reserve' buffer. 149 */ 150 fp->_ur = fp->_r; 151 fp->_up = fp->_p; 152 fp->_ub._base = fp->_ubuf; 153 fp->_ub._size = sizeof(fp->_ubuf); 154 fp->_ubuf[sizeof(fp->_ubuf) - 1] = c; 155 fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1]; 156 fp->_r = 1; 157 FUNLOCKFILE(fp); 158 return (c); 159 } 160