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 37 #if defined(LIBC_SCCS) && !defined(lint) 38 #if 0 39 static char sccsid[] = "@(#)ungetc.c 8.2 (Berkeley) 11/3/93"; 40 #endif 41 static const char rcsid[] = 42 "$FreeBSD$"; 43 #endif /* LIBC_SCCS and not lint */ 44 45 #include "namespace.h" 46 #include <stdio.h> 47 #include <stdlib.h> 48 #include <string.h> 49 #include "un-namespace.h" 50 #include "local.h" 51 #include "libc_private.h" 52 53 static int __submore __P((FILE *)); 54 55 /* 56 * Expand the ungetc buffer `in place'. That is, adjust fp->_p when 57 * the buffer moves, so that it points the same distance from the end, 58 * and move the bytes in the buffer around as necessary so that they 59 * are all at the end (stack-style). 60 */ 61 static int 62 __submore(FILE *fp) 63 { 64 int i; 65 unsigned char *p; 66 67 if (fp->_ub._base == fp->_ubuf) { 68 /* 69 * Get a new buffer (rather than expanding the old one). 70 */ 71 if ((p = malloc((size_t)BUFSIZ)) == NULL) 72 return (EOF); 73 fp->_ub._base = p; 74 fp->_ub._size = BUFSIZ; 75 p += BUFSIZ - sizeof(fp->_ubuf); 76 for (i = sizeof(fp->_ubuf); --i >= 0;) 77 p[i] = fp->_ubuf[i]; 78 fp->_p = p; 79 return (0); 80 } 81 i = fp->_ub._size; 82 p = realloc(fp->_ub._base, (size_t)(i << 1)); 83 if (p == NULL) 84 return (EOF); 85 /* no overlap (hence can use memcpy) because we doubled the size */ 86 (void)memcpy((void *)(p + i), (void *)p, (size_t)i); 87 fp->_p = p + i; 88 fp->_ub._base = p; 89 fp->_ub._size = i << 1; 90 return (0); 91 } 92 93 /* 94 * MT-safe version 95 */ 96 int 97 ungetc(int c, FILE *fp) 98 { 99 int ret; 100 101 if (c == EOF) 102 return (EOF); 103 if (!__sdidinit) 104 __sinit(); 105 FLOCKFILE(fp); 106 ret = __ungetc(c, fp); 107 FUNLOCKFILE(fp); 108 return (ret); 109 } 110 111 /* 112 * Non-MT-safe version 113 */ 114 int 115 __ungetc(int c, FILE *fp) 116 { 117 if (c == EOF) 118 return (EOF); 119 if ((fp->_flags & __SRD) == 0) { 120 /* 121 * Not already reading: no good unless reading-and-writing. 122 * Otherwise, flush any current write stuff. 123 */ 124 if ((fp->_flags & __SRW) == 0) 125 return (EOF); 126 if (fp->_flags & __SWR) { 127 if (__sflush(fp)) 128 return (EOF); 129 fp->_flags &= ~__SWR; 130 fp->_w = 0; 131 fp->_lbfsize = 0; 132 } 133 fp->_flags |= __SRD; 134 } 135 c = (unsigned char)c; 136 137 /* 138 * If we are in the middle of ungetc'ing, just continue. 139 * This may require expanding the current ungetc buffer. 140 */ 141 if (HASUB(fp)) { 142 if (fp->_r >= fp->_ub._size && __submore(fp)) 143 return (EOF); 144 *--fp->_p = c; 145 fp->_r++; 146 return (c); 147 } 148 fp->_flags &= ~__SEOF; 149 150 /* 151 * If we can handle this by simply backing up, do so, 152 * but never replace the original character. 153 * (This makes sscanf() work when scanning `const' data.) 154 */ 155 if (fp->_bf._base != NULL && fp->_p > fp->_bf._base && 156 fp->_p[-1] == c) { 157 fp->_p--; 158 fp->_r++; 159 return (c); 160 } 161 162 /* 163 * Create an ungetc buffer. 164 * Initially, we will use the `reserve' buffer. 165 */ 166 fp->_ur = fp->_r; 167 fp->_extra->_up = fp->_p; 168 fp->_ub._base = fp->_ubuf; 169 fp->_ub._size = sizeof(fp->_ubuf); 170 fp->_ubuf[sizeof(fp->_ubuf) - 1] = c; 171 fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1]; 172 fp->_r = 1; 173 return (c); 174 } 175