1/* $NetBSD: ungetc.c,v 1.16 2009/10/25 20:44:13 christos Exp $ */ 2 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#include <sys/cdefs.h> 36#if defined(LIBC_SCCS) && !defined(lint) 37#if 0 38static char sccsid[] = "@(#)ungetc.c 8.2 (Berkeley) 11/3/93"; 39#else 40__RCSID("$NetBSD: ungetc.c,v 1.16 2009/10/25 20:44:13 christos Exp $"); 41#endif 42#endif /* LIBC_SCCS and not lint */ 43 44#include <assert.h> 45#include <errno.h> 46#include <stdio.h> 47#include <stdlib.h> 48#include <string.h> 49#include "reentrant.h" 50#include "local.h" 51 52/* 53 * Expand the ungetc buffer `in place'. That is, adjust fp->_p when 54 * the buffer moves, so that it points the same distance from the end, 55 * and move the bytes in the buffer around as necessary so that they 56 * are all at the end (stack-style). 57 */ 58static int 59__submore(FILE *fp) 60{ 61 int i; 62 unsigned char *p; 63 64 _DIAGASSERT(fp != NULL); 65 66 if (_UB(fp)._base == fp->_ubuf) { 67 /* 68 * Get a new buffer (rather than expanding the old one). 69 */ 70 if ((p = malloc((size_t)BUFSIZ)) == NULL) 71 return EOF; 72 _UB(fp)._base = p; 73 _UB(fp)._size = BUFSIZ; 74 p += BUFSIZ - sizeof(fp->_ubuf); 75 for (i = sizeof(fp->_ubuf); --i >= 0;) 76 p[i] = fp->_ubuf[i]; 77 fp->_p = p; 78 return 0; 79 } 80 i = _UB(fp)._size; 81 p = realloc(_UB(fp)._base, (size_t)(i << 1)); 82 if (p == NULL) 83 return EOF; 84 /* no overlap (hence can use memcpy) because we doubled the size */ 85 (void)memcpy((p + i), p, (size_t)i); 86 fp->_p = p + i; 87 _UB(fp)._base = p; 88 _UB(fp)._size = i << 1; 89 return 0; 90} 91 92int 93ungetc(int c, FILE *fp) 94{ 95 96 _DIAGASSERT(fp != NULL); 97 98 if (c == EOF) 99 return EOF; 100 if (!__sdidinit) 101 __sinit(); 102 FLOCKFILE(fp); 103 _SET_ORIENTATION(fp, -1); 104 if ((fp->_flags & __SRD) == 0) { 105 /* 106 * Not already reading: no good unless reading-and-writing. 107 * Otherwise, flush any current write stuff. 108 */ 109 if ((fp->_flags & __SRW) == 0) { 110 FUNLOCKFILE(fp); 111 return EOF; 112 } 113 if (fp->_flags & __SWR) { 114 if (__sflush(fp)) { 115 FUNLOCKFILE(fp); 116 return EOF; 117 } 118 fp->_flags &= ~__SWR; 119 fp->_w = 0; 120 fp->_lbfsize = 0; 121 } 122 fp->_flags |= __SRD; 123 } 124 c = (unsigned char)c; 125 126 /* 127 * If we are in the middle of ungetc'ing, just continue. 128 * This may require expanding the current ungetc buffer. 129 */ 130 if (HASUB(fp)) { 131 if (fp->_r >= _UB(fp)._size && __submore(fp)) { 132 FUNLOCKFILE(fp); 133 return EOF; 134 } 135 *--fp->_p = c; 136 fp->_r++; 137 FUNLOCKFILE(fp); 138 return c; 139 } 140 fp->_flags &= ~__SEOF; 141 142 /* 143 * If we can handle this by simply backing up, do so, 144 * but never replace the original character. 145 * (This makes sscanf() work when scanning `const' data.) 146 */ 147 if (fp->_bf._base != NULL && fp->_p > fp->_bf._base && 148 fp->_p[-1] == c) { 149 fp->_p--; 150 fp->_r++; 151 FUNLOCKFILE(fp); 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 _UB(fp)._base = fp->_ubuf; 162 _UB(fp)._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 FUNLOCKFILE(fp); 167 return c; 168} 169