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 rcsid[] = "$OpenBSD: ungetc.c,v 1.4 2002/02/16 21:27:24 millert Exp $"; 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 46 static int __submore(FILE *); 47 /* 48 * Expand the ungetc buffer `in place'. That is, adjust fp->_p when 49 * the buffer moves, so that it points the same distance from the end, 50 * and move the bytes in the buffer around as necessary so that they 51 * are all at the end (stack-style). 52 */ 53 static int 54 __submore(fp) 55 FILE *fp; 56 { 57 register int i; 58 register unsigned char *p; 59 60 if (fp->_ub._base == fp->_ubuf) { 61 /* 62 * Get a new buffer (rather than expanding the old one). 63 */ 64 if ((p = malloc((size_t)BUFSIZ)) == NULL) 65 return (EOF); 66 fp->_ub._base = p; 67 fp->_ub._size = BUFSIZ; 68 p += BUFSIZ - sizeof(fp->_ubuf); 69 for (i = sizeof(fp->_ubuf); --i >= 0;) 70 p[i] = fp->_ubuf[i]; 71 fp->_p = p; 72 return (0); 73 } 74 i = fp->_ub._size; 75 p = realloc(fp->_ub._base, i << 1); 76 if (p == NULL) 77 return (EOF); 78 /* no overlap (hence can use memcpy) because we doubled the size */ 79 (void)memcpy((void *)(p + i), (void *)p, (size_t)i); 80 fp->_p = p + i; 81 fp->_ub._base = p; 82 fp->_ub._size = i << 1; 83 return (0); 84 } 85 86 int 87 ungetc(c, fp) 88 int c; 89 register FILE *fp; 90 { 91 if (c == EOF) 92 return (EOF); 93 if (!__sdidinit) 94 __sinit(); 95 if ((fp->_flags & __SRD) == 0) { 96 /* 97 * Not already reading: no good unless reading-and-writing. 98 * Otherwise, flush any current write stuff. 99 */ 100 if ((fp->_flags & __SRW) == 0) 101 return (EOF); 102 if (fp->_flags & __SWR) { 103 if (__sflush(fp)) 104 return (EOF); 105 fp->_flags &= ~__SWR; 106 fp->_w = 0; 107 fp->_lbfsize = 0; 108 } 109 fp->_flags |= __SRD; 110 } 111 c = (unsigned char)c; 112 113 /* 114 * If we are in the middle of ungetc'ing, just continue. 115 * This may require expanding the current ungetc buffer. 116 */ 117 if (HASUB(fp)) { 118 if (fp->_r >= fp->_ub._size && __submore(fp)) 119 return (EOF); 120 *--fp->_p = c; 121 fp->_r++; 122 return (c); 123 } 124 fp->_flags &= ~__SEOF; 125 126 /* 127 * If we can handle this by simply backing up, do so, 128 * but never replace the original character. 129 * (This makes sscanf() work when scanning `const' data.) 130 */ 131 if (fp->_bf._base != NULL && fp->_p > fp->_bf._base && 132 fp->_p[-1] == c) { 133 fp->_p--; 134 fp->_r++; 135 return (c); 136 } 137 138 /* 139 * Create an ungetc buffer. 140 * Initially, we will use the `reserve' buffer. 141 */ 142 fp->_ur = fp->_r; 143 fp->_up = fp->_p; 144 fp->_ub._base = fp->_ubuf; 145 fp->_ub._size = sizeof(fp->_ubuf); 146 fp->_ubuf[sizeof(fp->_ubuf) - 1] = c; 147 fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1]; 148 fp->_r = 1; 149 return (c); 150 } 151