1 /* $NetBSD: ungetc.c,v 1.14 2003/08/07 16:43:34 agc 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 38 static char sccsid[] = "@(#)ungetc.c 8.2 (Berkeley) 11/3/93"; 39 #else 40 __RCSID("$NetBSD: ungetc.c,v 1.14 2003/08/07 16:43:34 agc 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 static int __submore __P((FILE *)); 53 /* 54 * Expand the ungetc buffer `in place'. That is, adjust fp->_p when 55 * the buffer moves, so that it points the same distance from the end, 56 * and move the bytes in the buffer around as necessary so that they 57 * are all at the end (stack-style). 58 */ 59 static int 60 __submore(fp) 61 FILE *fp; 62 { 63 int i; 64 unsigned char *p; 65 66 _DIAGASSERT(fp != NULL); 67 68 if (_UB(fp)._base == fp->_ubuf) { 69 /* 70 * Get a new buffer (rather than expanding the old one). 71 */ 72 if ((p = malloc((size_t)BUFSIZ)) == NULL) 73 return (EOF); 74 _UB(fp)._base = p; 75 _UB(fp)._size = BUFSIZ; 76 p += BUFSIZ - sizeof(fp->_ubuf); 77 for (i = sizeof(fp->_ubuf); --i >= 0;) 78 p[i] = fp->_ubuf[i]; 79 fp->_p = p; 80 return (0); 81 } 82 i = _UB(fp)._size; 83 p = realloc(_UB(fp)._base, (size_t)(i << 1)); 84 if (p == NULL) 85 return (EOF); 86 /* no overlap (hence can use memcpy) because we doubled the size */ 87 (void)memcpy((void *)(p + i), (void *)p, (size_t)i); 88 fp->_p = p + i; 89 _UB(fp)._base = p; 90 _UB(fp)._size = i << 1; 91 return (0); 92 } 93 94 int 95 ungetc(c, fp) 96 int c; 97 FILE *fp; 98 { 99 100 _DIAGASSERT(fp != NULL); 101 102 if (c == EOF) 103 return (EOF); 104 if (!__sdidinit) 105 __sinit(); 106 FLOCKFILE(fp); 107 _SET_ORIENTATION(fp, -1); 108 if ((fp->_flags & __SRD) == 0) { 109 /* 110 * Not already reading: no good unless reading-and-writing. 111 * Otherwise, flush any current write stuff. 112 */ 113 if ((fp->_flags & __SRW) == 0) { 114 FUNLOCKFILE(fp); 115 return (EOF); 116 } 117 if (fp->_flags & __SWR) { 118 if (__sflush(fp)) { 119 FUNLOCKFILE(fp); 120 return (EOF); 121 } 122 fp->_flags &= ~__SWR; 123 fp->_w = 0; 124 fp->_lbfsize = 0; 125 } 126 fp->_flags |= __SRD; 127 } 128 c = (unsigned char)c; 129 130 /* 131 * If we are in the middle of ungetc'ing, just continue. 132 * This may require expanding the current ungetc buffer. 133 */ 134 if (HASUB(fp)) { 135 if (fp->_r >= _UB(fp)._size && __submore(fp)) { 136 FUNLOCKFILE(fp); 137 return (EOF); 138 } 139 *--fp->_p = c; 140 fp->_r++; 141 FUNLOCKFILE(fp); 142 return (c); 143 } 144 fp->_flags &= ~__SEOF; 145 146 /* 147 * If we can handle this by simply backing up, do so, 148 * but never replace the original character. 149 * (This makes sscanf() work when scanning `const' data.) 150 */ 151 if (fp->_bf._base != NULL && fp->_p > fp->_bf._base && 152 fp->_p[-1] == c) { 153 fp->_p--; 154 fp->_r++; 155 FUNLOCKFILE(fp); 156 return (c); 157 } 158 159 /* 160 * Create an ungetc buffer. 161 * Initially, we will use the `reserve' buffer. 162 */ 163 fp->_ur = fp->_r; 164 fp->_up = fp->_p; 165 _UB(fp)._base = fp->_ubuf; 166 _UB(fp)._size = sizeof(fp->_ubuf); 167 fp->_ubuf[sizeof(fp->_ubuf) - 1] = c; 168 fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1]; 169 fp->_r = 1; 170 FUNLOCKFILE(fp); 171 return (c); 172 } 173