ungetc.c revision 13545
11573Srgrimes/*- 21573Srgrimes * Copyright (c) 1990, 1993 31573Srgrimes * The Regents of the University of California. All rights reserved. 41573Srgrimes * 51573Srgrimes * This code is derived from software contributed to Berkeley by 61573Srgrimes * Chris Torek. 71573Srgrimes * 81573Srgrimes * Redistribution and use in source and binary forms, with or without 91573Srgrimes * modification, are permitted provided that the following conditions 101573Srgrimes * are met: 111573Srgrimes * 1. Redistributions of source code must retain the above copyright 121573Srgrimes * notice, this list of conditions and the following disclaimer. 131573Srgrimes * 2. Redistributions in binary form must reproduce the above copyright 141573Srgrimes * notice, this list of conditions and the following disclaimer in the 151573Srgrimes * documentation and/or other materials provided with the distribution. 161573Srgrimes * 3. All advertising materials mentioning features or use of this software 171573Srgrimes * must display the following acknowledgement: 181573Srgrimes * This product includes software developed by the University of 191573Srgrimes * California, Berkeley and its contributors. 201573Srgrimes * 4. Neither the name of the University nor the names of its contributors 211573Srgrimes * may be used to endorse or promote products derived from this software 221573Srgrimes * without specific prior written permission. 231573Srgrimes * 241573Srgrimes * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 251573Srgrimes * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 261573Srgrimes * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 271573Srgrimes * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 281573Srgrimes * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 291573Srgrimes * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 301573Srgrimes * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 311573Srgrimes * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 321573Srgrimes * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 331573Srgrimes * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 341573Srgrimes * SUCH DAMAGE. 351573Srgrimes */ 361573Srgrimes 371573Srgrimes#if defined(LIBC_SCCS) && !defined(lint) 381573Srgrimesstatic char sccsid[] = "@(#)ungetc.c 8.2 (Berkeley) 11/3/93"; 391573Srgrimes#endif /* LIBC_SCCS and not lint */ 401573Srgrimes 411573Srgrimes#include <stdio.h> 421573Srgrimes#include <stdlib.h> 431573Srgrimes#include <string.h> 441573Srgrimes#include "local.h" 4513545Sjulian#ifdef _THREAD_SAFE 4613545Sjulian#include <pthread.h> 4713545Sjulian#include "pthread_private.h" 4813545Sjulian#endif 491573Srgrimes 501573Srgrimes/* 511573Srgrimes * Expand the ungetc buffer `in place'. That is, adjust fp->_p when 521573Srgrimes * the buffer moves, so that it points the same distance from the end, 531573Srgrimes * and move the bytes in the buffer around as necessary so that they 541573Srgrimes * are all at the end (stack-style). 551573Srgrimes */ 5613545Sjulianstatic int 571573Srgrimes__submore(fp) 581573Srgrimes register FILE *fp; 591573Srgrimes{ 601573Srgrimes register int i; 611573Srgrimes register unsigned char *p; 621573Srgrimes 631573Srgrimes if (fp->_ub._base == fp->_ubuf) { 641573Srgrimes /* 651573Srgrimes * Get a new buffer (rather than expanding the old one). 661573Srgrimes */ 671573Srgrimes if ((p = malloc((size_t)BUFSIZ)) == NULL) 681573Srgrimes return (EOF); 691573Srgrimes fp->_ub._base = p; 701573Srgrimes fp->_ub._size = BUFSIZ; 711573Srgrimes p += BUFSIZ - sizeof(fp->_ubuf); 721573Srgrimes for (i = sizeof(fp->_ubuf); --i >= 0;) 731573Srgrimes p[i] = fp->_ubuf[i]; 741573Srgrimes fp->_p = p; 751573Srgrimes return (0); 761573Srgrimes } 771573Srgrimes i = fp->_ub._size; 781573Srgrimes p = realloc(fp->_ub._base, i << 1); 791573Srgrimes if (p == NULL) 801573Srgrimes return (EOF); 811573Srgrimes /* no overlap (hence can use memcpy) because we doubled the size */ 821573Srgrimes (void)memcpy((void *)(p + i), (void *)p, (size_t)i); 831573Srgrimes fp->_p = p + i; 841573Srgrimes fp->_ub._base = p; 851573Srgrimes fp->_ub._size = i << 1; 861573Srgrimes return (0); 871573Srgrimes} 881573Srgrimes 8913545Sjulianint 901573Srgrimesungetc(c, fp) 911573Srgrimes int c; 921573Srgrimes register FILE *fp; 931573Srgrimes{ 941573Srgrimes if (c == EOF) 951573Srgrimes return (EOF); 961573Srgrimes if (!__sdidinit) 971573Srgrimes __sinit(); 9813545Sjulian#ifdef _THREAD_SAFE 9913545Sjulian _thread_flockfile(fp,__FILE__,__LINE__); 10013545Sjulian#endif 1011573Srgrimes if ((fp->_flags & __SRD) == 0) { 1021573Srgrimes /* 1031573Srgrimes * Not already reading: no good unless reading-and-writing. 1041573Srgrimes * Otherwise, flush any current write stuff. 1051573Srgrimes */ 10613545Sjulian if ((fp->_flags & __SRW) == 0) { 10713545Sjulian#ifdef _THREAD_SAFE 10813545Sjulian _thread_funlockfile(fp); 10913545Sjulian#endif 1101573Srgrimes return (EOF); 11113545Sjulian } 1121573Srgrimes if (fp->_flags & __SWR) { 11313545Sjulian if (__sflush(fp)) { 11413545Sjulian#ifdef _THREAD_SAFE 11513545Sjulian _thread_funlockfile(fp); 11613545Sjulian#endif 1171573Srgrimes return (EOF); 11813545Sjulian } 1191573Srgrimes fp->_flags &= ~__SWR; 1201573Srgrimes fp->_w = 0; 1211573Srgrimes fp->_lbfsize = 0; 1221573Srgrimes } 1231573Srgrimes fp->_flags |= __SRD; 1241573Srgrimes } 1251573Srgrimes c = (unsigned char)c; 1261573Srgrimes 1271573Srgrimes /* 1281573Srgrimes * If we are in the middle of ungetc'ing, just continue. 1291573Srgrimes * This may require expanding the current ungetc buffer. 1301573Srgrimes */ 1311573Srgrimes if (HASUB(fp)) { 13213545Sjulian if (fp->_r >= fp->_ub._size && __submore(fp)) { 13313545Sjulian#ifdef _THREAD_SAFE 13413545Sjulian _thread_funlockfile(fp); 13513545Sjulian#endif 1361573Srgrimes return (EOF); 13713545Sjulian } 1381573Srgrimes *--fp->_p = c; 1391573Srgrimes fp->_r++; 14013545Sjulian#ifdef _THREAD_SAFE 14113545Sjulian _thread_funlockfile(fp); 14213545Sjulian#endif 1431573Srgrimes return (c); 1441573Srgrimes } 1451573Srgrimes fp->_flags &= ~__SEOF; 1461573Srgrimes 1471573Srgrimes /* 1481573Srgrimes * If we can handle this by simply backing up, do so, 1491573Srgrimes * but never replace the original character. 1501573Srgrimes * (This makes sscanf() work when scanning `const' data.) 1511573Srgrimes */ 1521573Srgrimes if (fp->_bf._base != NULL && fp->_p > fp->_bf._base && 1531573Srgrimes fp->_p[-1] == c) { 1541573Srgrimes fp->_p--; 1551573Srgrimes fp->_r++; 15613545Sjulian#ifdef _THREAD_SAFE 15713545Sjulian _thread_funlockfile(fp); 15813545Sjulian#endif 1591573Srgrimes return (c); 1601573Srgrimes } 1611573Srgrimes 1621573Srgrimes /* 1631573Srgrimes * Create an ungetc buffer. 1641573Srgrimes * Initially, we will use the `reserve' buffer. 1651573Srgrimes */ 1661573Srgrimes fp->_ur = fp->_r; 1671573Srgrimes fp->_up = fp->_p; 1681573Srgrimes fp->_ub._base = fp->_ubuf; 1691573Srgrimes fp->_ub._size = sizeof(fp->_ubuf); 1701573Srgrimes fp->_ubuf[sizeof(fp->_ubuf) - 1] = c; 1711573Srgrimes fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1]; 1721573Srgrimes fp->_r = 1; 17313545Sjulian#ifdef _THREAD_SAFE 17413545Sjulian _thread_funlockfile(fp); 17513545Sjulian#endif 1761573Srgrimes return (c); 1771573Srgrimes} 178