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 "$Id$"; 43 #endif /* LIBC_SCCS and not lint */ 44 45 #include <stdio.h> 46 #include <stdlib.h> 47 #include <string.h> 48 #include "local.h" 49 #ifdef _THREAD_SAFE 50 #include <pthread.h> 51 #include "pthread_private.h" 52 #endif 53 54 static int __submore __P((FILE *)); 55 56 /* 57 * Expand the ungetc buffer `in place'. That is, adjust fp->_p when 58 * the buffer moves, so that it points the same distance from the end, 59 * and move the bytes in the buffer around as necessary so that they 60 * are all at the end (stack-style). 61 */ 62 static int 63 __submore(fp) 64 register FILE *fp; 65 { 66 register int i; 67 register unsigned char *p; 68 69 if (fp->_ub._base == fp->_ubuf) { 70 /* 71 * Get a new buffer (rather than expanding the old one). 72 */ 73 if ((p = malloc((size_t)BUFSIZ)) == NULL) 74 return (EOF); 75 fp->_ub._base = p; 76 fp->_ub._size = BUFSIZ; 77 p += BUFSIZ - sizeof(fp->_ubuf); 78 for (i = sizeof(fp->_ubuf); --i >= 0;) 79 p[i] = fp->_ubuf[i]; 80 fp->_p = p; 81 return (0); 82 } 83 i = fp->_ub._size; 84 p = realloc(fp->_ub._base, (size_t)(i << 1)); 85 if (p == NULL) 86 return (EOF); 87 /* no overlap (hence can use memcpy) because we doubled the size */ 88 (void)memcpy((void *)(p + i), (void *)p, (size_t)i); 89 fp->_p = p + i; 90 fp->_ub._base = p; 91 fp->_ub._size = i << 1; 92 return (0); 93 } 94 95 int 96 ungetc(c, fp) 97 int c; 98 register FILE *fp; 99 { 100 if (c == EOF) 101 return (EOF); 102 if (!__sdidinit) 103 __sinit(); 104 #ifdef _THREAD_SAFE 105 _thread_flockfile(fp,__FILE__,__LINE__); 106 #endif 107 if ((fp->_flags & __SRD) == 0) { 108 /* 109 * Not already reading: no good unless reading-and-writing. 110 * Otherwise, flush any current write stuff. 111 */ 112 if ((fp->_flags & __SRW) == 0) { 113 #ifdef _THREAD_SAFE 114 _thread_funlockfile(fp); 115 #endif 116 return (EOF); 117 } 118 if (fp->_flags & __SWR) { 119 if (__sflush(fp)) { 120 #ifdef _THREAD_SAFE 121 _thread_funlockfile(fp); 122 #endif 123 return (EOF); 124 } 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 #ifdef _THREAD_SAFE 140 _thread_funlockfile(fp); 141 #endif 142 return (EOF); 143 } 144 *--fp->_p = c; 145 fp->_r++; 146 #ifdef _THREAD_SAFE 147 _thread_funlockfile(fp); 148 #endif 149 return (c); 150 } 151 fp->_flags &= ~__SEOF; 152 153 /* 154 * If we can handle this by simply backing up, do so, 155 * but never replace the original character. 156 * (This makes sscanf() work when scanning `const' data.) 157 */ 158 if (fp->_bf._base != NULL && fp->_p > fp->_bf._base && 159 fp->_p[-1] == c) { 160 fp->_p--; 161 fp->_r++; 162 #ifdef _THREAD_SAFE 163 _thread_funlockfile(fp); 164 #endif 165 return (c); 166 } 167 168 /* 169 * Create an ungetc buffer. 170 * Initially, we will use the `reserve' buffer. 171 */ 172 fp->_ur = fp->_r; 173 fp->_up = fp->_p; 174 fp->_ub._base = fp->_ubuf; 175 fp->_ub._size = sizeof(fp->_ubuf); 176 fp->_ubuf[sizeof(fp->_ubuf) - 1] = c; 177 fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1]; 178 fp->_r = 1; 179 #ifdef _THREAD_SAFE 180 _thread_funlockfile(fp); 181 #endif 182 return (c); 183 } 184