portable getch( )

[The Brain]

Trying to make my own version of getch( ) that will work like <conio.h>'s getch( ) where a character can be removed from the keyboard buffer without having to wait for a newline/carriage return.

Here is what I've come up with so far. The code looks like it should work; however, the program does not seem to respond to any keyboard inputs:

#include<iostream>
#include<cctype>
#include<string>
#include<windows.h>
using namespace std;

char getch();

int main()
{
    do{       
          
          cout << "\nEnter something: ";
          
          cout << getch();
          
          cout << "\n\nWould ye' like to try again? (Y/N) ";
          
    }while(toupper(getch())!='N');
    
    return 0;
}


char getch()
{
     HANDLE hIn;
     INPUT_RECORD InRec; 
     DWORD EventCount, fdwSaveOldMode; 
          
     hIn = GetStdHandle(STD_INPUT_HANDLE); 
     
     GetConsoleMode(hIn, &fdwSaveOldMode);
     
     SetConsoleMode(hIn, ENABLE_ECHO_INPUT|ENABLE_LINE_INPUT);      
             
     
     for(;;)
     {      
         GetNumberOfConsoleInputEvents(hIn, &EventCount);
         
         if(EventCount)
         {         
              ReadConsoleInput(hIn, &InRec, 1, NULL);        
         
              if(InRec.EventType == KEY_EVENT)
              {          
                   SetConsoleMode(hIn, fdwSaveOldMode);                     
                   return static_cast<signed char>(InRec.Event.KeyEvent.uChar.AsciiChar);  
              }  
         }             
     }
}

Additional info:

My usage of SetConsoleMode( ) is based on this MSDN excerpt:

ENABLE_LINE_INPUT
0x0002 The ReadFile or ReadConsole function returns only when a carriage return character is read. If this mode is disabled, the functions return when one or more characters are available.

ENABLE_ECHO_INPUT
0x0004 Characters read by the ReadFile or ReadConsole function are written to the active screen buffer as they are read. This mode can be used only if the ENABLE_LINE_INPUT mode is also enabled.

[Codeplug]

A couple of things:
- ReadConsoleInput() doesn't say that NULL is valid for the last parameter.
- Don't poll for input. It's not nice to eat up the CPU.
- Don't bother with ENABLE_ECHO_INPUT and ENABLE_LINE_INPUT - they don't affect ReadConsoleInput().

int getch()
{
    HANDLE hIn = GetStdHandle(STD_INPUT_HANDLE);
    if (!hIn)
        return -1;

    DWORD fdwSaveOldMode;
    if (!GetConsoleMode(hIn, &fdwSaveOldMode) ||
        !SetConsoleMode(hIn, 0))
        return -1;

    int c = -1;

    while (1)
    {
        if (WaitForSingleObject(hIn, INFINITE) != WAIT_OBJECT_0)
            break;
        
        INPUT_RECORD InRec;
        DWORD numRead;
        if (!ReadConsoleInput(hIn, &InRec, 1, &numRead))
            break;

        if ((InRec.EventType == KEY_EVENT) &&
            InRec.Event.KeyEvent.bKeyDown)
        {
            c = InRec.Event.KeyEvent.uChar.AsciiChar;
            break;
        }//if
    }//while

    SetConsoleMode(hIn, fdwSaveOldMode);

    return c;
}//getch

This is still a long ways off from mimicking the MS getch() behavour.

gg

[Br5an]

I had a little password input routine that I converted over to getch( ) and getche( ). getche( ) is the same except with character echo to screen. I guess it's similar to what's already posted but then again I guess it should be. It easy to modify by expanding or limiting input around isprint(...); It's been so long since I used Turbo C++ getch( ) that I don't actually remember what key-presses should be responded to.

Regards,
Brian

char getch(void)  
{
	DWORD dwCharsRead;
	INPUT_RECORD inRec;
	HANDLE hInput = GetStdHandle(STD_INPUT_HANDLE);
	 
	while(ReadConsoleInput(hInput, &inRec, 1, &dwCharsRead))  
		if(inRec.EventType == KEY_EVENT && inRec.Event.KeyEvent.bKeyDown
			&& isprint(inRec.Event.KeyEvent.uChar.AsciiChar))
				return(inRec.Event.KeyEvent.uChar.AsciiChar);
		
	return('ì'); // dummy return to suppress warning msg.
}

char getche(void)  
{  
	INPUT_RECORD inRec;
	char buffer[2] = {'\0'};
	DWORD dwCharsRead, dwCharsWritten;
	HANDLE hInput = GetStdHandle(STD_INPUT_HANDLE);  
	HANDLE hOutput = GetStdHandle(STD_OUTPUT_HANDLE);  
	 
	while(ReadConsoleInput(hInput, &inRec, 1, &dwCharsRead))  
		if(inRec.EventType == KEY_EVENT && inRec.Event.KeyEvent.bKeyDown
			&& isprint(inRec.Event.KeyEvent.uChar.AsciiChar))
		{
			buffer[0] = inRec.Event.KeyEvent.uChar.AsciiChar;
			WriteConsole(hOutput, buffer, 1, &dwCharsWritten, NULL);
			return(inRec.Event.KeyEvent.uChar.AsciiChar);
		}
		
	return('ì'); // dummy return to suppress warning msg.
}

#include <windows.h>
#include <iostream>
#include <cstdlib>

using namespace std;

/* Password function for Win32 console  
* reads keystrokes but displays * to mask printable entries  
* first parameter: a pointer to a char array, buffer to hold password  
* second parameter: password buffer size, including null terminator  
* return value: funtion returns 1 if max buffer is reached, else returns 0  
*/  
 
int Password( char * buffer, int buffSize)  
{  
	int count = 0;  
	INPUT_RECORD inRec;  
	HANDLE hInput, hOutput;  
	DWORD dwCharsRead, dwCharsWritten;  
	 
	buffSize--;  
	hInput = GetStdHandle(STD_INPUT_HANDLE);  
	hOutput = GetStdHandle(STD_OUTPUT_HANDLE);  
	 
	while(ReadConsoleInput(hInput, &inRec, 1, &dwCharsRead) && count < buffSize)  
		if(inRec.EventType == KEY_EVENT && inRec.Event.KeyEvent.bKeyDown == TRUE)  
			if(isprint(inRec.Event.KeyEvent.uChar.AsciiChar))  
				buffer[count++] = inRec.Event.KeyEvent.uChar.AsciiChar,  
				WriteConsole(hOutput, "*", 1, &dwCharsWritten, NULL);  
			else  
			if(inRec.Event.KeyEvent.uChar.AsciiChar == '\b' && count > 0)  
				WriteConsole(hOutput, "\b \b", 3, &dwCharsWritten, NULL),  
				count--;  
			else  
			if(inRec.Event.KeyEvent.uChar.AsciiChar == '\r')  
				break;  
	 
	buffer[count] = '\0';  
	 
	if(count == buffSize)  
	return(1);  
	else  
	return(0);  
}  

int main( int argc, char * argv[] )
{
	char buffer[256];
	
	cout << endl << endl << "Enter Password: ";
	Password(buffer, 256);
	
	return(0);
}