244 lines
6.6 KiB
C
244 lines
6.6 KiB
C
/* ungetc.c - return a character to a stream. stdio.h */
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/* Copyright 1992-1993 Wind River Systems, Inc. */
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/*
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modification history
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--------------------
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01c,05mar93,jdi documentation cleanup for 5.1.
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01b,20sep92,smb documentation additions
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01a,29jul92,jcf Added OBJ_VERIFY
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+smb taken from UCB stdio
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*/
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/*
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DESCRIPTION
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* Copyright (c) 1990 The Regents of the University of California.
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* All rights reserved.
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*
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* This code is derived from software contributed to Berkeley by
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* Chris Torek.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* 3. All advertising materials mentioning features or use of this software
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* must display the following acknowledgement:
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* This product includes software developed by the University of
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* California, Berkeley and its contributors.
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* 4. Neither the name of the University nor the names of its contributors
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* may be used to endorse or promote products derived from this software
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* without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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* ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
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* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
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* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
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* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
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* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
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* SUCH DAMAGE.
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INCLUDE FILE: stdio.h, stdlib.h, string.h
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SEE ALSO: American National Standard X3.159-1989
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NOMANUAL
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*/
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#include "vxWorks.h"
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#include "stdio.h"
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#include "stdlib.h"
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#include "string.h"
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#include "objLib.h"
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#include "private/stdioP.h"
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/******************************************************************************
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*
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* __submore - internal routine
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*
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* Expand the ungetc buffer `in place'. That is, adjust fp->_p when
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* the buffer moves, so that it points the same distance from the end,
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* and move the bytes in the buffer around as necessary so that they
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* are all at the end (stack-style).
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*
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* INCLUDE FILES: stdio.h
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*
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* RETURNS:
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* NOMANUAL
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*/
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static int __submore
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(
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FAST FILE *fp
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)
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{
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FAST int i;
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FAST uchar_t * p;
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if (fp->_ub._base == fp->_ubuf)
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{
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/* Get a new buffer (rather than expanding the old one) */
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if ((p = malloc ((size_t)BUFSIZ)) == NULL)
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return (EOF);
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fp->_ub._base = p;
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fp->_ub._size = BUFSIZ;
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p += BUFSIZ - sizeof(fp->_ubuf);
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for (i = sizeof(fp->_ubuf); --i >= 0;)
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p[i] = fp->_ubuf[i];
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fp->_p = p;
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return (0);
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}
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i = fp->_ub._size;
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p = realloc (fp->_ub._base, i << 1);
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if (p == NULL)
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return (EOF);
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(void) bcopy ((void *)p, (void *)(p + i), (size_t)i);
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fp->_p = p + i;
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fp->_ub._base = p;
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fp->_ub._size = i << 1;
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return (0);
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}
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/******************************************************************************
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*
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* ungetc - push a character back into an input stream (ANSI)
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*
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* This routine pushes a character <c> (converted to an `unsigned char') back
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* into the specified input stream. The pushed-back characters will be
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* returned by subsequent reads on that stream in the reverse order of their
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* pushing. A successful intervening call on the stream to a file
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* positioning function (fseek(), fsetpos(), or rewind()) discards any
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* pushed-back characters for the stream. The external storage corresponding
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* to the stream is unchanged.
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*
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* One character of push-back is guaranteed. If ungetc() is called too many
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* times on the same stream without an intervening read or file positioning
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* operation, the operation may fail.
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*
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* If the value of <c> equals EOF, the operation fails and the
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* input stream is unchanged.
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*
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* A successful call to ungetc() clears the end-of-file indicator for the
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* stream. The value of the file position indicator for the stream after
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* reading or discarding all pushed-back characters is the same as it was
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* before the character were pushed back. For a text stream, the value of
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* its file position indicator after a successful call to ungetc() is
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* unspecified until all pushed-back characters are read or discarded.
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* For a binary stream, the file position indicator is decremented by each
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* successful call to ungetc(); if its value was zero before a call, it is
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* indeterminate after the call.
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*
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* INCLUDE: stdio.h
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*
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* RETURNS:
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* The pushed-back character after conversion, or EOF if the operation fails.
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*
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* SEE ALSO: getc(), fgetc()
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*/
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int ungetc
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(
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int c, /* character to push */
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FAST FILE * fp /* input stream */
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)
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{
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if (OBJ_VERIFY (fp, fpClassId) != OK)
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return (EOF);
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if (c == EOF)
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return (EOF);
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if ((fp->_flags & __SRD) == 0)
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{
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/*
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* Not already reading: no good unless reading-and-writing.
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* Otherwise, flush any current write stuff.
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*/
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if ((fp->_flags & __SRW) == 0)
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return (EOF);
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if (fp->_flags & __SWR)
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{
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if (__sflush(fp))
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return (EOF);
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fp->_flags &= ~__SWR;
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fp->_w = 0;
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fp->_lbfsize = 0;
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}
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fp->_flags |= __SRD;
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}
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c = (uchar_t) c;
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/*
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* If we are in the middle of ungetc'ing, just continue.
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* This may require expanding the current ungetc buffer.
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*/
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if (HASUB(fp))
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{
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if (fp->_r >= fp->_ub._size && __submore(fp))
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return (EOF);
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*--fp->_p = c;
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fp->_r++;
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return (c);
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}
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/*
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* If we can handle this by simply backing up, do so,
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* but never replace the original character.
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* (This makes sscanf() work when scanning `const' data.)
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*/
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if ((fp->_bf._base != NULL) &&
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(fp->_p > fp->_bf._base) &&
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(fp->_p[-1] == c))
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{
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fp->_p--;
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fp->_r++;
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return (c);
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}
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/*
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* Create an ungetc buffer.
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* Initially, we will use the `reserve' buffer.
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*/
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fp->_ur = fp->_r;
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fp->_up = fp->_p;
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fp->_ub._base = fp->_ubuf;
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fp->_ub._size = sizeof(fp->_ubuf);
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fp->_ubuf[sizeof(fp->_ubuf) - 1] = c;
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fp->_p = &fp->_ubuf[sizeof(fp->_ubuf) - 1];
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fp->_r = 1;
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return (c);
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}
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