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Commit	Line	Data
	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	* 4. Neither the name of the University nor the names of its contributors
	17	* may be used to endorse or promote products derived from this software
	18	* without specific prior written permission.
	19	*
	20	* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
	21	* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
	22	* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
	23	* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
	24	* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
	25	* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
	26	* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
	27	* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
	28	* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
	29	* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
	30	* SUCH DAMAGE.
	31	*/
	32
	33	#if defined(LIBC_SCCS) && !defined(lint)
	34	static char sccsid[] = "@(#)ungetc.c 8.2 (Berkeley) 11/3/93";
	35	#endif /* LIBC_SCCS and not lint */
	36	#include <sys/cdefs.h>
	37	__FBSDID("$FreeBSD: src/lib/libc/stdio/ungetc.c,v 1.18 2008/04/17 22:17:54 jhb Exp $");
	38
	39	#include "namespace.h"
	40	#include <stdio.h>
	41	#include <stdlib.h>
	42	#include <string.h>
	43	#include "un-namespace.h"
	44	#include "local.h"
	45	#include "libc_private.h"
	46
	47	static int __submore(FILE *);
	48
	49	/*
	50	* Expand the ungetc buffer `in place'. That is, adjust fp->_p when
	51	* the buffer moves, so that it points the same distance from the end,
	52	* and move the bytes in the buffer around as necessary so that they
	53	* are all at the end (stack-style).
	54	*/
	55	static int
	56	__submore(FILE *fp)
	57	{
	58	int i;
	59	unsigned char *p;
	60
	61	if (fp->_ub._base == fp->_ubuf) {
	62	/*
	63	* Get a new buffer (rather than expanding the old one).
	64	*/
	65	if ((p = malloc((size_t)BUFSIZ)) == NULL)
	66	return (EOF);
	67	fp->_ub._base = p;
	68	fp->_ub._size = BUFSIZ;
	69	p += BUFSIZ - sizeof(fp->_ubuf);
	70	for (i = sizeof(fp->_ubuf); --i >= 0;)
	71	p[i] = fp->_ubuf[i];
	72	fp->_p = p;
	73	return (0);
	74	}
	75	i = fp->_ub._size;
	76	p = realloc(fp->_ub._base, (size_t)(i << 1));
	77	if (p == NULL)
	78	return (EOF);
	79	/* no overlap (hence can use memcpy) because we doubled the size */
	80	(void)memcpy((void )(p + i), (void )p, (size_t)i);
	81	fp->_p = p + i;
	82	fp->_ub._base = p;
	83	fp->_ub._size = i << 1;
	84	return (0);
	85	}
	86
	87	/*
	88	* MT-safe version
	89	*/
	90	int
	91	ungetc(int c, FILE *fp)
	92	{
	93	int ret;
	94
	95	pthread_once(&__sdidinit, __sinit);
	96
	97	FLOCKFILE(fp);
	98	ORIENT(fp, -1);
	99	ret = __ungetc(c, fp);
	100	FUNLOCKFILE(fp);
	101	return (ret);
	102	}
	103
	104	/*
	105	* Non-MT-safe version
	106	*/
	107	int
	108	__ungetc(int c, FILE *fp)
	109	{
	110
	111	if (c == EOF)
	112	return (EOF);
	113	if ((fp->_flags & __SRD) == 0) {
	114	/*
	115	* Not already reading: no good unless reading-and-writing.
	116	* Otherwise, flush any current write stuff.
	117	*/
	118	if ((fp->_flags & __SRW) == 0)
	119	return (EOF);
	120	if (fp->_flags & __SWR) {
	121	if (__sflush(fp))
	122	return (EOF);
	123	fp->_flags &= ~__SWR;
	124	fp->_w = 0;
	125	fp->_lbfsize = 0;
	126	}
	127	fp->_flags \|= __SRD;
	128	}
	129	c = (unsigned char)c;
	130
	131	/*
	132	* If we are in the middle of ungetc'ing, just continue.
	133	* This may require expanding the current ungetc buffer.
	134	*/
	135	if (HASUB(fp)) {
	136	if (fp->_r >= fp->_ub._size && __submore(fp))
	137	return (EOF);
	138	*--fp->_p = c;
	139	fp->_r++;
	140	return (c);
	141	}
	142	fp->_flags &= ~__SEOF;
	143
	144	/*
	145	* If we can handle this by simply backing up, do so,
	146	* but never replace the original character.
	147	* (This makes sscanf() work when scanning `const' data.)
	148	*/
	149	if (fp->_bf._base != NULL && fp->_p > fp->_bf._base &&
	150	fp->_p[-1] == c) {
	151	fp->_p--;
	152	fp->_r++;
	153	return (c);
	154	}
	155
	156	/*
	157	* Create an ungetc buffer.
	158	* Initially, we will use the `reserve' buffer.
	159	*/
	160	fp->_ur = fp->_r;
	161	fp->_up = fp->_p;
	162	fp->_ub._base = fp->_ubuf;
	163	fp->_ub._size = sizeof(fp->_ubuf);
	164	fp->_ubuf[sizeof(fp->_ubuf) - 1] = c;
	165	fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1];
	166	fp->_r = 1;
	167	return (c);
	168	}