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// getwch.cpp
//
// Copyright (c) Microsoft Corporation. All rights reserved.
//
// Defines _getwch(), _getwche(), and _ungetwch(), which get and unget
// characters directly from the console.
//
#include <conio.h>
#include <corecrt_internal_lowio.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <wchar.h>
namespace
{
struct CharPair
{
unsigned char LeadChar;
unsigned char SecondChar;
};
}
static wint_t wchbuf = WEOF; // The push-back buffer
extern "C" extern intptr_t __dcrt_lowio_console_input_handle;
extern "C" CharPair const* __cdecl _getextendedkeycode(KEY_EVENT_RECORD*);
// Reads one character directly from the console. The _getwche() form also
// echoes the character back to the console. If the push-back buffer is
// nonempty, then its value is returned and the push-back buffer is marked as
// empty.
//
// Returns the character that is read on success; returns WEOF on failure.
extern "C" wint_t __cdecl _getwch()
{
__acrt_lock(__acrt_conio_lock);
wint_t result = 0;
__try
{
result = _getwch_nolock();
}
__finally
{
__acrt_unlock(__acrt_conio_lock);
}
return result;
}
extern "C" wint_t __cdecl _getwche()
{
__acrt_lock(__acrt_conio_lock);
wint_t result = 0;
__try
{
result = _getwche_nolock();
}
__finally
{
__acrt_unlock(__acrt_conio_lock);
}
return result;
}
extern "C" wint_t __cdecl _getwch_nolock()
{
// First check the pushback buffer for a character. If it has one, return
// it without echoing and reset the buffer:
if (wchbuf != WEOF)
{
wchar_t const buffered_wchar = static_cast<wchar_t>(wchbuf & 0xFFFF);
wchbuf = WEOF;
return buffered_wchar;
}
// The console input handle is created the first time that _getwch(),
// _cgetws(), or _kbhit() is called:
if (__dcrt_lowio_ensure_console_input_initialized() == FALSE)
return WEOF;
// Switch to raw mode (no line input, no echo input):
DWORD old_console_mode;
__dcrt_get_input_console_mode(&old_console_mode);
__dcrt_set_input_console_mode(0);
wint_t result = 0;
__try
{
for ( ; ; )
{
// Get a console input event:
INPUT_RECORD input_record;
DWORD num_read;
if (__dcrt_read_console_input(&input_record, 1, &num_read) == FALSE)
{
result = WEOF;
__leave;
}
if (num_read == 0)
{
result = WEOF;
__leave;
}
// Look for, and decipher, key events.
if (input_record.EventType == KEY_EVENT && input_record.Event.KeyEvent.bKeyDown)
{
// Easy case: if UnicodeChar is non-zero, we can just return it:
wchar_t const c = static_cast<wchar_t>(input_record.Event.KeyEvent.uChar.UnicodeChar);
if (c != 0)
{
result = c;
__leave;
}
// Hard case: either it is an extended code or an event which
// should not be recognized. Let _getextendedkeycode do the work:
CharPair const* const cp = _getextendedkeycode(&input_record.Event.KeyEvent);
if (cp != nullptr)
{
wchbuf = cp->SecondChar;
result = cp->LeadChar;
__leave;
}
}
}
}
__finally
{
// Restore the previous console mode:
__dcrt_set_input_console_mode(old_console_mode);
}
return result;
}
extern "C" wint_t __cdecl _getwche_nolock()
{
// First check the pushback buffer for a character. If it has one, return
// it without echoing and reset the buffer:
if (wchbuf != WEOF)
{
wchar_t const buffered_wchar = static_cast<wchar_t>(wchbuf & 0xFFFF);
wchbuf = WEOF;
return buffered_wchar;
}
// Othwrwise, read the character, echo it, and return it. If anything fails,
// we immediately return WEOF.
wchar_t const gotten_wchar = _getwch_nolock();
if (gotten_wchar == WEOF)
return WEOF;
if (_putwch_nolock(gotten_wchar) == WEOF)
return WEOF;
return gotten_wchar;
}
// Pushes back ("ungets") one character to be read next by _getwch() or
// _getwche(). On success, returns the character that was pushed back; on
// failure, returns EOF.
extern "C" wint_t __cdecl _ungetwch(wint_t const c)
{
__acrt_lock(__acrt_conio_lock);
wint_t result = 0;
__try
{
result = _ungetwch_nolock(c);
}
__finally
{
__acrt_unlock(__acrt_conio_lock);
}
return result;
}
extern "C" wint_t __cdecl _ungetwch_nolock(wint_t const c)
{
// Fail if the char is EOF or the pushback buffer is non-empty:
if (c == WEOF || wchbuf != WEOF)
return static_cast<wint_t>(EOF);
wchbuf = (c & 0xFF);
return wchbuf;
}
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