ungetc.c revision 71579
1353095Skevans/*- 2353095Skevans * Copyright (c) 1990, 1993 3353095Skevans * The Regents of the University of California. All rights reserved. 4353095Skevans * 5353095Skevans * This code is derived from software contributed to Berkeley by 6353095Skevans * Chris Torek. 7353095Skevans * 8353095Skevans * Redistribution and use in source and binary forms, with or without 9353095Skevans * modification, are permitted provided that the following conditions 10353095Skevans * are met: 11353095Skevans * 1. Redistributions of source code must retain the above copyright 12353095Skevans * notice, this list of conditions and the following disclaimer. 13353095Skevans * 2. Redistributions in binary form must reproduce the above copyright 14353095Skevans * notice, this list of conditions and the following disclaimer in the 15353095Skevans * documentation and/or other materials provided with the distribution. 16353095Skevans * 3. All advertising materials mentioning features or use of this software 17353095Skevans * must display the following acknowledgement: 18353095Skevans * This product includes software developed by the University of 19353095Skevans * California, Berkeley and its contributors. 20353095Skevans * 4. Neither the name of the University nor the names of its contributors 21353095Skevans * may be used to endorse or promote products derived from this software 22353095Skevans * without specific prior written permission. 23353095Skevans * 24353095Skevans * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25353095Skevans * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26353095Skevans * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27353095Skevans * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28353095Skevans * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29353095Skevans * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30353095Skevans * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31353095Skevans * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32353095Skevans * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33353095Skevans * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34353095Skevans * SUCH DAMAGE. 35353095Skevans */ 36353095Skevans 37353095Skevans#if defined(LIBC_SCCS) && !defined(lint) 38353095Skevans#if 0 39353095Skevansstatic char sccsid[] = "@(#)ungetc.c 8.2 (Berkeley) 11/3/93"; 40353095Skevans#endif 41353095Skevansstatic const char rcsid[] = 42353095Skevans "$FreeBSD: head/lib/libc/stdio/ungetc.c 71579 2001-01-24 13:01:12Z deischen $"; 43353095Skevans#endif /* LIBC_SCCS and not lint */ 44353095Skevans 45353095Skevans#include "namespace.h" 46353095Skevans#include <stdio.h> 47353095Skevans#include <stdlib.h> 48353095Skevans#include <string.h> 49353095Skevans#include "un-namespace.h" 50353095Skevans#include "local.h" 51353095Skevans#include "libc_private.h" 52353095Skevans 53353095Skevansstatic int __submore __P((FILE *)); 54353095Skevans 55353095Skevans/* 56353095Skevans * Expand the ungetc buffer `in place'. That is, adjust fp->_p when 57353095Skevans * the buffer moves, so that it points the same distance from the end, 58353095Skevans * and move the bytes in the buffer around as necessary so that they 59353095Skevans * are all at the end (stack-style). 60353095Skevans */ 61353095Skevansstatic int 62353095Skevans__submore(FILE *fp) 63353095Skevans{ 64353095Skevans int i; 65353095Skevans unsigned char *p; 66353095Skevans 67353095Skevans if (fp->_ub._base == fp->_ubuf) { 68353095Skevans /* 69353095Skevans * Get a new buffer (rather than expanding the old one). 70353095Skevans */ 71353095Skevans if ((p = malloc((size_t)BUFSIZ)) == NULL) 72353095Skevans return (EOF); 73353095Skevans fp->_ub._base = p; 74353095Skevans fp->_ub._size = BUFSIZ; 75353095Skevans p += BUFSIZ - sizeof(fp->_ubuf); 76353095Skevans for (i = sizeof(fp->_ubuf); --i >= 0;) 77353095Skevans p[i] = fp->_ubuf[i]; 78353095Skevans fp->_p = p; 79353095Skevans return (0); 80353095Skevans } 81353095Skevans i = fp->_ub._size; 82353095Skevans p = realloc(fp->_ub._base, (size_t)(i << 1)); 83353095Skevans if (p == NULL) 84353095Skevans return (EOF); 85353095Skevans /* no overlap (hence can use memcpy) because we doubled the size */ 86353095Skevans (void)memcpy((void *)(p + i), (void *)p, (size_t)i); 87353095Skevans fp->_p = p + i; 88353095Skevans fp->_ub._base = p; 89353095Skevans fp->_ub._size = i << 1; 90353095Skevans return (0); 91353095Skevans} 92353095Skevans 93353095Skevans/* 94353095Skevans * MT-safe version 95353095Skevans */ 96353095Skevansint 97353095Skevansungetc(int c, FILE *fp) 98353095Skevans{ 99353095Skevans int ret; 100353095Skevans 101353095Skevans if (c == EOF) 102353095Skevans return (EOF); 103353095Skevans if (!__sdidinit) 104353095Skevans __sinit(); 105353095Skevans FLOCKFILE(fp); 106353095Skevans ret = __ungetc(c, fp); 107353095Skevans FUNLOCKFILE(fp); 108353095Skevans return (ret); 109353095Skevans} 110353095Skevans 111353095Skevans/* 112353095Skevans * Non-MT-safe version 113353095Skevans */ 114353095Skevansint 115353095Skevans__ungetc(int c, FILE *fp) 116353095Skevans{ 117353095Skevans if (c == EOF) 118353095Skevans return (EOF); 119353095Skevans if ((fp->_flags & __SRD) == 0) { 120353095Skevans /* 121353095Skevans * Not already reading: no good unless reading-and-writing. 122353095Skevans * Otherwise, flush any current write stuff. 123353095Skevans */ 124353095Skevans if ((fp->_flags & __SRW) == 0) 125353095Skevans return (EOF); 126353095Skevans if (fp->_flags & __SWR) { 127353095Skevans if (__sflush(fp)) 128353095Skevans return (EOF); 129353095Skevans fp->_flags &= ~__SWR; 130353095Skevans fp->_w = 0; 131353095Skevans fp->_lbfsize = 0; 132353095Skevans } 133353095Skevans fp->_flags |= __SRD; 134353095Skevans } 135353095Skevans c = (unsigned char)c; 136353095Skevans 137353095Skevans /* 138353095Skevans * If we are in the middle of ungetc'ing, just continue. 139353095Skevans * This may require expanding the current ungetc buffer. 140353095Skevans */ 141353095Skevans if (HASUB(fp)) { 142 if (fp->_r >= fp->_ub._size && __submore(fp)) 143 return (EOF); 144 *--fp->_p = c; 145 fp->_r++; 146 return (c); 147 } 148 fp->_flags &= ~__SEOF; 149 150 /* 151 * If we can handle this by simply backing up, do so, 152 * but never replace the original character. 153 * (This makes sscanf() work when scanning `const' data.) 154 */ 155 if (fp->_bf._base != NULL && fp->_p > fp->_bf._base && 156 fp->_p[-1] == c) { 157 fp->_p--; 158 fp->_r++; 159 return (c); 160 } 161 162 /* 163 * Create an ungetc buffer. 164 * Initially, we will use the `reserve' buffer. 165 */ 166 fp->_ur = fp->_r; 167 fp->_up = fp->_p; 168 fp->_ub._base = fp->_ubuf; 169 fp->_ub._size = sizeof(fp->_ubuf); 170 fp->_ubuf[sizeof(fp->_ubuf) - 1] = c; 171 fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1]; 172 fp->_r = 1; 173 return (c); 174} 175