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 #include "namespace.h" 40 #include <stdio.h> 41 #include <stdlib.h> 42 #include <string.h> 43 #include "un-namespace.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 = reallocarray(fp->_ub._base, i, 2); 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 * 2; 84 return (0); 85 } 86 87 /* 88 * MT-safe version 89 */ 90 int 91 ungetc(int c, FILE *fp) 92 { 93 int ret; 94 95 if (!__sdidinit) 96 __sinit(); 97 FLOCKFILE_CANCELSAFE(fp); 98 ORIENT(fp, -1); 99 ret = __ungetc(c, fp); 100 FUNLOCKFILE_CANCELSAFE(); 101 return (ret); 102 } 103 104 /* 105 * Non-MT-safe version 106 */ 107 int 108 __ungetc(int c, FILE *fp) 109 { 110 111 if (c == EOF) 112 return (EOF); 113 if ((fp->_flags & __SRD) == 0) { 114 /* 115 * Not already reading: no good unless reading-and-writing. 116 * Otherwise, flush any current write stuff. 117 */ 118 if ((fp->_flags & __SRW) == 0) 119 return (EOF); 120 if (fp->_flags & __SWR) { 121 if (__sflush(fp)) 122 return (EOF); 123 fp->_flags &= ~__SWR; 124 fp->_w = 0; 125 fp->_lbfsize = 0; 126 } 127 fp->_flags |= __SRD; 128 } 129 c = (unsigned char)c; 130 131 /* 132 * If we are in the middle of ungetc'ing, just continue. 133 * This may require expanding the current ungetc buffer. 134 */ 135 if (HASUB(fp)) { 136 if (fp->_r >= fp->_ub._size && __submore(fp)) 137 return (EOF); 138 *--fp->_p = c; 139 fp->_r++; 140 return (c); 141 } 142 fp->_flags &= ~__SEOF; 143 144 /* 145 * If we can handle this by simply backing up, do so, 146 * but never replace the original character. 147 * (This makes sscanf() work when scanning `const' data.) 148 */ 149 if (fp->_bf._base != NULL && fp->_p > fp->_bf._base && 150 fp->_p[-1] == c) { 151 fp->_p--; 152 fp->_r++; 153 return (c); 154 } 155 156 /* 157 * Create an ungetc buffer. 158 * Initially, we will use the `reserve' buffer. 159 */ 160 fp->_ur = fp->_r; 161 fp->_up = fp->_p; 162 fp->_ub._base = fp->_ubuf; 163 fp->_ub._size = sizeof(fp->_ubuf); 164 fp->_ubuf[sizeof(fp->_ubuf) - 1] = c; 165 fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1]; 166 fp->_r = 1; 167 return (c); 168 } 169