/***
*ungetc.c - unget a character from a stream
*
* Copyright (c) 1993, Microsoft Corporation. All rights reserved.
*
*Purpose:
* defines ungetc() - pushes a character back onto an input stream
*
*Revision History:
* 04-26-93 CFW Module created.
* 04-30-93 CFW Bring wide char support from ungetc.c.
* 05-10-93 CFW Optimize, fix error handling.
* 06-02-93 CFW Wide get/put use wint_t.
* 07-16-93 SRW ALPHA Merge
*
*******************************************************************************/
#include <cruntime.h>
#include <stdio.h>
#include <file2.h>
#include <assert.h>
#include <internal.h>
#include <os2dll.h>
#include <msdos.h>
#include <errno.h>
#include <wchar.h>
#include <setlocal.h>
#ifdef MTHREAD /* multi-thread; define both ungetwc and _lk_ungetwc */
/***
*wint_t ungetwc(ch, stream) - put a wide character back onto a stream
*
*Purpose:
* Guaranteed one char pushback on a stream as long as open for reading.
* More than one char pushback in a row is not guaranteed, and will fail
* if it follows an ungetc which pushed the first char in buffer. Failure
* causes return of WEOF.
*
*Entry:
* wint_t ch - wide character to push back
* FILE *stream - stream to push character onto
*
*Exit:
* returns ch
* returns WEOF if tried to push WEOF, stream not opened for reading or
* or if we have already ungetc'd back to beginning of buffer.
*
*Exceptions:
*
*******************************************************************************/
wint_t _CRTAPI1 ungetwc (
REG2 wint_t ch,
REG1 FILE *stream
)
{
wint_t retval;
int index;
assert(stream != NULL);
index = _iob_index(stream);
_lock_str(index);
retval = _ungetwc_lk (ch, stream);
_unlock_str(index);
return(retval);
}
/***
*_ungetwc_lk() - Ungetwc() core routine (locked version)
*
*Purpose:
* Core ungetwc() routine; assumes stream is already locked.
*
* [See ungetwc() above for more info.]
*
*Entry: [See ungetwc()]
*
*Exit: [See ungetwc()]
*
*Exceptions:
*
*******************************************************************************/
wint_t _CRTAPI1 _ungetwc_lk (
wint_t ch,
FILE *str
)
{
#else /* non multi-thread; just define ungetc */
wint_t _CRTAPI1 ungetwc (
wint_t ch,
FILE *str
)
{
#endif /* rejoin common code */
assert(str != NULL);
/*
* Requirements for success:
*
* 1. Character to be pushed back on the stream must not be WEOF.
*
* 2. The stream must currently be in read mode, or must be open for
* update (i.e., read/write) and must NOT currently be in write
* mode.
*/
if ( (ch != WEOF) &&
( (str->_flag & _IOREAD) || ((str->_flag & _IORW) &&
!(str->_flag & _IOWRT))
)
)
{
/* If stream is unbuffered, get one. */
if (str->_base == NULL)
_getbuf(str);
#ifndef _NTSUBSET_
if (!(str->_flag & _IOSTRG) && _osfile[_fileno(str)] & FTEXT)
{
/*
* Text mode, sigh... Convert the wc to a mbc.
*/
int size, defused;
char mbc[4];
size = WideCharToMultiByte(_lc_codepage,
WC_COMPOSITECHECK | WC_SEPCHARS,
(wchar_t *)&ch,
1,
mbc,
MB_CUR_MAX,
NULL,
&defused);
if ( (size == 0) || defused )
{
/*
* Conversion failed! Set errno and return
* failure.
*/
errno = EILSEQ;
return WEOF;
}
/* we know _base != NULL; since file is buffered */
if (str->_ptr == str->_base)
{
if (str->_cnt)
/* my back is against the wall; i've already done
* ungetwc, and there's no room for this one
*/
return WEOF;
str->_ptr += size;
}
if ( size == 1 )
{
*--str->_ptr = mbc[0];
}
else /* size == 2 */
{
*--str->_ptr = mbc[1];
*--str->_ptr = mbc[0];
}
str->_cnt += size;
str->_flag &= ~_IOEOF;
str->_flag |= _IOREAD; /* may already be set */
return (wint_t) (0x0ffff & ch);
}
#endif
/*
* Binary mode - push back the wide char.
*/
/* we know _base != NULL; since file is buffered */
if (str->_ptr == str->_base)
{
if (str->_cnt)
/* my back is against the wall; i've already done
* ungetc, and there's no room for this one
*/
return WEOF;
str->_ptr += sizeof(wchar_t);
}
str->_cnt += sizeof(wchar_t);
str->_flag &= ~_IOEOF;
str->_flag |= _IOREAD; /* may already be set */
return (wint_t) (*--((wchar_t *)(str->_ptr)) = (wchar_t)(ch & 0xffff));
}
return WEOF;
}
