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 #include "namespace.h" 36 #include <stdio.h> 37 #include <stdlib.h> 38 #include <string.h> 39 #include "un-namespace.h" 40 #include "local.h" 41 #include "libc_private.h" 42 43 static int __submore(FILE *); 44 45 /* 46 * Expand the ungetc buffer `in place'. That is, adjust fp->_p when 47 * the buffer moves, so that it points the same distance from the end, 48 * and move the bytes in the buffer around as necessary so that they 49 * are all at the end (stack-style). 50 */ 51 static int 52 __submore(FILE *fp) 53 { 54 int i; 55 unsigned char *p; 56 57 if (fp->_ub._base == fp->_ubuf) { 58 /* 59 * Get a new buffer (rather than expanding the old one). 60 */ 61 if ((p = malloc((size_t)BUFSIZ)) == NULL) 62 return (EOF); 63 fp->_ub._base = p; 64 fp->_ub._size = BUFSIZ; 65 p += BUFSIZ - sizeof(fp->_ubuf); 66 for (i = sizeof(fp->_ubuf); --i >= 0;) 67 p[i] = fp->_ubuf[i]; 68 fp->_p = p; 69 return (0); 70 } 71 i = fp->_ub._size; 72 p = reallocarray(fp->_ub._base, i, 2); 73 if (p == NULL) 74 return (EOF); 75 /* no overlap (hence can use memcpy) because we doubled the size */ 76 (void)memcpy((void *)(p + i), (void *)p, (size_t)i); 77 fp->_p = p + i; 78 fp->_ub._base = p; 79 fp->_ub._size = i * 2; 80 return (0); 81 } 82 83 /* 84 * MT-safe version 85 */ 86 int 87 ungetc(int c, FILE *fp) 88 { 89 int ret; 90 91 if (!__sdidinit) 92 __sinit(); 93 FLOCKFILE_CANCELSAFE(fp); 94 ORIENT(fp, -1); 95 ret = __ungetc(c, fp); 96 FUNLOCKFILE_CANCELSAFE(); 97 return (ret); 98 } 99 100 /* 101 * Non-MT-safe version 102 */ 103 int 104 __ungetc(int c, FILE *fp) 105 { 106 107 if (c == EOF) 108 return (EOF); 109 if ((fp->_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->_flags & __SRW) == 0) 115 return (EOF); 116 if (fp->_flags & __SWR) { 117 if (__sflush(fp)) 118 return (EOF); 119 fp->_flags &= ~__SWR; 120 fp->_w = 0; 121 fp->_lbfsize = 0; 122 } 123 fp->_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->_r >= fp->_ub._size && __submore(fp)) 133 return (EOF); 134 *--fp->_p = c; 135 fp->_r++; 136 return (c); 137 } 138 fp->_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->_p > fp->_bf._base && 146 fp->_p[-1] == c) { 147 fp->_p--; 148 fp->_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->_r; 157 fp->_up = fp->_p; 158 fp->_ub._base = fp->_ubuf; 159 fp->_ub._size = sizeof(fp->_ubuf); 160 fp->_ubuf[sizeof(fp->_ubuf) - 1] = c; 161 fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1]; 162 fp->_r = 1; 163 return (c); 164 } 165