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 <stdio.h> 46 #include <stdlib.h> 47 #include <string.h> 48 #include "local.h" 49 #include "libc_private.h" 50 51 static int __submore __P((FILE *)); 52 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 register FILE *fp; 62 { 63 register int i; 64 register unsigned char *p; 65 66 if (fp->_ub._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 fp->_ub._base = p; 73 fp->_ub._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 = fp->_ub._size; 81 p = realloc(fp->_ub._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((void *)(p + i), (void *)p, (size_t)i); 86 fp->_p = p + i; 87 fp->_ub._base = p; 88 fp->_ub._size = i << 1; 89 return (0); 90 } 91 92 int 93 ungetc(c, fp) 94 int c; 95 register FILE *fp; 96 { 97 if (c == EOF) 98 return (EOF); 99 if (!__sdidinit) 100 __sinit(); 101 FLOCKFILE(fp); 102 if ((fp->_flags & __SRD) == 0) { 103 /* 104 * Not already reading: no good unless reading-and-writing. 105 * Otherwise, flush any current write stuff. 106 */ 107 if ((fp->_flags & __SRW) == 0) { 108 FUNLOCKFILE(fp); 109 return (EOF); 110 } 111 if (fp->_flags & __SWR) { 112 if (__sflush(fp)) { 113 FUNLOCKFILE(fp); 114 return (EOF); 115 } 116 fp->_flags &= ~__SWR; 117 fp->_w = 0; 118 fp->_lbfsize = 0; 119 } 120 fp->_flags |= __SRD; 121 } 122 c = (unsigned char)c; 123 124 /* 125 * If we are in the middle of ungetc'ing, just continue. 126 * This may require expanding the current ungetc buffer. 127 */ 128 if (HASUB(fp)) { 129 if (fp->_r >= fp->_ub._size && __submore(fp)) { 130 FUNLOCKFILE(fp); 131 return (EOF); 132 } 133 *--fp->_p = c; 134 fp->_r++; 135 FUNLOCKFILE(fp); 136 return (c); 137 } 138 fp->_flags &= ~__SEOF; 139 140 /* 141 * If we can handle this by simply backing up, do so, 142 * but never replace the original character. 143 * (This makes sscanf() work when scanning `const' data.) 144 */ 145 if (fp->_bf._base != NULL && fp->_p > fp->_bf._base && 146 fp->_p[-1] == c) { 147 fp->_p--; 148 fp->_r++; 149 FUNLOCKFILE(fp); 150 return (c); 151 } 152 153 /* 154 * Create an ungetc buffer. 155 * Initially, we will use the `reserve' buffer. 156 */ 157 fp->_ur = fp->_r; 158 fp->_up = fp->_p; 159 fp->_ub._base = fp->_ubuf; 160 fp->_ub._size = sizeof(fp->_ubuf); 161 fp->_ubuf[sizeof(fp->_ubuf) - 1] = c; 162 fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1]; 163 fp->_r = 1; 164 FUNLOCKFILE(fp); 165 return (c); 166 } 167