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 static char sccsid[] = "@(#)ungetc.c 8.2 (Berkeley) 11/3/93"; 39 #endif /* LIBC_SCCS and not lint */ 40 #include <sys/cdefs.h> 41 __FBSDID("$FreeBSD$"); 42 43 #include "namespace.h" 44 #include <stdio.h> 45 #include <stdlib.h> 46 #include <string.h> 47 #include "un-namespace.h" 48 #include "local.h" 49 #include "libc_private.h" 50 51 static int __submore(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(FILE *fp) 61 { 62 int i; 63 unsigned char *p; 64 65 if (fp->_ub._base == fp->_ubuf) { 66 /* 67 * Get a new buffer (rather than expanding the old one). 68 */ 69 if ((p = malloc((size_t)BUFSIZ)) == NULL) 70 return (EOF); 71 fp->_ub._base = p; 72 fp->_ub._size = BUFSIZ; 73 p += BUFSIZ - sizeof(fp->_ubuf); 74 for (i = sizeof(fp->_ubuf); --i >= 0;) 75 p[i] = fp->_ubuf[i]; 76 fp->_p = p; 77 return (0); 78 } 79 i = fp->_ub._size; 80 p = realloc(fp->_ub._base, (size_t)(i << 1)); 81 if (p == NULL) 82 return (EOF); 83 /* no overlap (hence can use memcpy) because we doubled the size */ 84 (void)memcpy((void *)(p + i), (void *)p, (size_t)i); 85 fp->_p = p + i; 86 fp->_ub._base = p; 87 fp->_ub._size = i << 1; 88 return (0); 89 } 90 91 /* 92 * MT-safe version 93 */ 94 int 95 ungetc(int c, FILE *fp) 96 { 97 int ret; 98 99 if (!__sdidinit) 100 __sinit(); 101 FLOCKFILE(fp); 102 ORIENT(fp, -1); 103 ret = __ungetc(c, fp); 104 FUNLOCKFILE(fp); 105 return (ret); 106 } 107 108 /* 109 * Non-MT-safe version 110 */ 111 int 112 __ungetc(int c, FILE *fp) 113 { 114 115 if (c == EOF) 116 return (EOF); 117 if ((fp->_flags & __SRD) == 0) { 118 /* 119 * Not already reading: no good unless reading-and-writing. 120 * Otherwise, flush any current write stuff. 121 */ 122 if ((fp->_flags & __SRW) == 0) 123 return (EOF); 124 if (fp->_flags & __SWR) { 125 if (__sflush(fp)) 126 return (EOF); 127 fp->_flags &= ~__SWR; 128 fp->_w = 0; 129 fp->_lbfsize = 0; 130 } 131 fp->_flags |= __SRD; 132 } 133 c = (unsigned char)c; 134 135 /* 136 * If we are in the middle of ungetc'ing, just continue. 137 * This may require expanding the current ungetc buffer. 138 */ 139 if (HASUB(fp)) { 140 if (fp->_r >= fp->_ub._size && __submore(fp)) 141 return (EOF); 142 *--fp->_p = c; 143 fp->_r++; 144 return (c); 145 } 146 fp->_flags &= ~__SEOF; 147 148 /* 149 * If we can handle this by simply backing up, do so, 150 * but never replace the original character. 151 * (This makes sscanf() work when scanning `const' data.) 152 */ 153 if (fp->_bf._base != NULL && fp->_p > fp->_bf._base && 154 fp->_p[-1] == c) { 155 fp->_p--; 156 fp->_r++; 157 return (c); 158 } 159 160 /* 161 * Create an ungetc buffer. 162 * Initially, we will use the `reserve' buffer. 163 */ 164 fp->_ur = fp->_r; 165 fp->_extra->_up = fp->_p; 166 fp->_ub._base = fp->_ubuf; 167 fp->_ub._size = sizeof(fp->_ubuf); 168 fp->_ubuf[sizeof(fp->_ubuf) - 1] = c; 169 fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1]; 170 fp->_r = 1; 171 return (c); 172 } 173