ungetc.c revision 13545
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) 38static char sccsid[] = "@(#)ungetc.c 8.2 (Berkeley) 11/3/93"; 39#endif /* LIBC_SCCS and not lint */ 40 41#include <stdio.h> 42#include <stdlib.h> 43#include <string.h> 44#include "local.h" 45#ifdef _THREAD_SAFE 46#include <pthread.h> 47#include "pthread_private.h" 48#endif 49 50/* 51 * Expand the ungetc buffer `in place'. That is, adjust fp->_p when 52 * the buffer moves, so that it points the same distance from the end, 53 * and move the bytes in the buffer around as necessary so that they 54 * are all at the end (stack-style). 55 */ 56static int 57__submore(fp) 58 register FILE *fp; 59{ 60 register int i; 61 register unsigned char *p; 62 63 if (fp->_ub._base == fp->_ubuf) { 64 /* 65 * Get a new buffer (rather than expanding the old one). 66 */ 67 if ((p = malloc((size_t)BUFSIZ)) == NULL) 68 return (EOF); 69 fp->_ub._base = p; 70 fp->_ub._size = BUFSIZ; 71 p += BUFSIZ - sizeof(fp->_ubuf); 72 for (i = sizeof(fp->_ubuf); --i >= 0;) 73 p[i] = fp->_ubuf[i]; 74 fp->_p = p; 75 return (0); 76 } 77 i = fp->_ub._size; 78 p = realloc(fp->_ub._base, i << 1); 79 if (p == NULL) 80 return (EOF); 81 /* no overlap (hence can use memcpy) because we doubled the size */ 82 (void)memcpy((void *)(p + i), (void *)p, (size_t)i); 83 fp->_p = p + i; 84 fp->_ub._base = p; 85 fp->_ub._size = i << 1; 86 return (0); 87} 88 89int 90ungetc(c, fp) 91 int c; 92 register FILE *fp; 93{ 94 if (c == EOF) 95 return (EOF); 96 if (!__sdidinit) 97 __sinit(); 98#ifdef _THREAD_SAFE 99 _thread_flockfile(fp,__FILE__,__LINE__); 100#endif 101 if ((fp->_flags & __SRD) == 0) { 102 /* 103 * Not already reading: no good unless reading-and-writing. 104 * Otherwise, flush any current write stuff. 105 */ 106 if ((fp->_flags & __SRW) == 0) { 107#ifdef _THREAD_SAFE 108 _thread_funlockfile(fp); 109#endif 110 return (EOF); 111 } 112 if (fp->_flags & __SWR) { 113 if (__sflush(fp)) { 114#ifdef _THREAD_SAFE 115 _thread_funlockfile(fp); 116#endif 117 return (EOF); 118 } 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#ifdef _THREAD_SAFE 134 _thread_funlockfile(fp); 135#endif 136 return (EOF); 137 } 138 *--fp->_p = c; 139 fp->_r++; 140#ifdef _THREAD_SAFE 141 _thread_funlockfile(fp); 142#endif 143 return (c); 144 } 145 fp->_flags &= ~__SEOF; 146 147 /* 148 * If we can handle this by simply backing up, do so, 149 * but never replace the original character. 150 * (This makes sscanf() work when scanning `const' data.) 151 */ 152 if (fp->_bf._base != NULL && fp->_p > fp->_bf._base && 153 fp->_p[-1] == c) { 154 fp->_p--; 155 fp->_r++; 156#ifdef _THREAD_SAFE 157 _thread_funlockfile(fp); 158#endif 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->_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#ifdef _THREAD_SAFE 174 _thread_funlockfile(fp); 175#endif 176 return (c); 177} 178