1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1990, 1993 5 * The Regents of the University of California. All rights reserved. 6 * 7 * This code is derived from software contributed to Berkeley by 8 * Chris Torek. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 3. Neither the name of the University nor the names of its contributors 19 * may be used to endorse or promote products derived from this software 20 * without specific prior written permission. 21 * 22 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32 * SUCH DAMAGE. 33 */ 34 35 #if defined(LIBC_SCCS) && !defined(lint) 36 static char sccsid[] = "@(#)ungetc.c 8.2 (Berkeley) 11/3/93"; 37 #endif /* LIBC_SCCS and not lint */ 38 #include <sys/cdefs.h> 39 __FBSDID("$FreeBSD$"); 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 = reallocarray(fp->_ub._base, i, 2); 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 * 2; 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 (!__sdidinit) 98 __sinit(); 99 FLOCKFILE_CANCELSAFE(fp); 100 ORIENT(fp, -1); 101 ret = __ungetc(c, fp); 102 FUNLOCKFILE_CANCELSAFE(); 103 return (ret); 104 } 105 106 /* 107 * Non-MT-safe version 108 */ 109 int 110 __ungetc(int c, FILE *fp) 111 { 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 if (fp->_flags & __SWR) { 123 if (__sflush(fp)) 124 return (EOF); 125 fp->_flags &= ~__SWR; 126 fp->_w = 0; 127 fp->_lbfsize = 0; 128 } 129 fp->_flags |= __SRD; 130 } 131 c = (unsigned char)c; 132 133 /* 134 * If we are in the middle of ungetc'ing, just continue. 135 * This may require expanding the current ungetc buffer. 136 */ 137 if (HASUB(fp)) { 138 if (fp->_r >= fp->_ub._size && __submore(fp)) 139 return (EOF); 140 *--fp->_p = c; 141 fp->_r++; 142 return (c); 143 } 144 fp->_flags &= ~__SEOF; 145 146 /* 147 * If we can handle this by simply backing up, do so, 148 * but never replace the original character. 149 * (This makes sscanf() work when scanning `const' data.) 150 */ 151 if (fp->_bf._base != NULL && fp->_p > fp->_bf._base && 152 fp->_p[-1] == c) { 153 fp->_p--; 154 fp->_r++; 155 return (c); 156 } 157 158 /* 159 * Create an ungetc buffer. 160 * Initially, we will use the `reserve' buffer. 161 */ 162 fp->_ur = fp->_r; 163 fp->_up = fp->_p; 164 fp->_ub._base = fp->_ubuf; 165 fp->_ub._size = sizeof(fp->_ubuf); 166 fp->_ubuf[sizeof(fp->_ubuf) - 1] = c; 167 fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1]; 168 fp->_r = 1; 169 return (c); 170 } 171