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 "namespace.h" 39 #include <stdio.h> 40 #include <stdlib.h> 41 #include <string.h> 42 #include "un-namespace.h" 43 #include "local.h" 44 #include "libc_private.h" 45 46 static int __submore(FILE *); 47 48 /* 49 * Expand the ungetc buffer `in place'. That is, adjust fp->_p when 50 * the buffer moves, so that it points the same distance from the end, 51 * and move the bytes in the buffer around as necessary so that they 52 * are all at the end (stack-style). 53 */ 54 static int 55 __submore(FILE *fp) 56 { 57 int i; 58 unsigned char *p; 59 60 if (fp->_ub._base == fp->_ubuf) { 61 /* 62 * Get a new buffer (rather than expanding the old one). 63 */ 64 if ((p = malloc((size_t)BUFSIZ)) == NULL) 65 return (EOF); 66 fp->_ub._base = p; 67 fp->_ub._size = BUFSIZ; 68 p += BUFSIZ - sizeof(fp->_ubuf); 69 for (i = sizeof(fp->_ubuf); --i >= 0;) 70 p[i] = fp->_ubuf[i]; 71 fp->_p = p; 72 return (0); 73 } 74 i = fp->_ub._size; 75 p = reallocarray(fp->_ub._base, i, 2); 76 if (p == NULL) 77 return (EOF); 78 /* no overlap (hence can use memcpy) because we doubled the size */ 79 (void)memcpy((void *)(p + i), (void *)p, (size_t)i); 80 fp->_p = p + i; 81 fp->_ub._base = p; 82 fp->_ub._size = i * 2; 83 return (0); 84 } 85 86 /* 87 * MT-safe version 88 */ 89 int 90 ungetc(int c, FILE *fp) 91 { 92 int ret; 93 94 if (!__sdidinit) 95 __sinit(); 96 FLOCKFILE_CANCELSAFE(fp); 97 ORIENT(fp, -1); 98 ret = __ungetc(c, fp); 99 FUNLOCKFILE_CANCELSAFE(); 100 return (ret); 101 } 102 103 /* 104 * Non-MT-safe version 105 */ 106 int 107 __ungetc(int c, FILE *fp) 108 { 109 110 if (c == EOF) 111 return (EOF); 112 if ((fp->_flags & __SRD) == 0) { 113 /* 114 * Not already reading: no good unless reading-and-writing. 115 * Otherwise, flush any current write stuff. 116 */ 117 if ((fp->_flags & __SRW) == 0) 118 return (EOF); 119 if (fp->_flags & __SWR) { 120 if (__sflush(fp)) 121 return (EOF); 122 fp->_flags &= ~__SWR; 123 fp->_w = 0; 124 fp->_lbfsize = 0; 125 } 126 fp->_flags |= __SRD; 127 } 128 c = (unsigned char)c; 129 130 /* 131 * If we are in the middle of ungetc'ing, just continue. 132 * This may require expanding the current ungetc buffer. 133 */ 134 if (HASUB(fp)) { 135 if (fp->_r >= fp->_ub._size && __submore(fp)) 136 return (EOF); 137 *--fp->_p = c; 138 fp->_r++; 139 return (c); 140 } 141 fp->_flags &= ~__SEOF; 142 143 /* 144 * If we can handle this by simply backing up, do so, 145 * but never replace the original character. 146 * (This makes sscanf() work when scanning `const' data.) 147 */ 148 if (fp->_bf._base != NULL && fp->_p > fp->_bf._base && 149 fp->_p[-1] == c) { 150 fp->_p--; 151 fp->_r++; 152 return (c); 153 } 154 155 /* 156 * Create an ungetc buffer. 157 * Initially, we will use the `reserve' buffer. 158 */ 159 fp->_ur = fp->_r; 160 fp->_up = fp->_p; 161 fp->_ub._base = fp->_ubuf; 162 fp->_ub._size = sizeof(fp->_ubuf); 163 fp->_ubuf[sizeof(fp->_ubuf) - 1] = c; 164 fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1]; 165 fp->_r = 1; 166 return (c); 167 } 168