portable getch( )

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:

Code:

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#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); 
              } 
        }           
    }
}

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Additional info:

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

Quote:

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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.

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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().

Code:

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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

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

gg

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

Code:

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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.
}

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Code:

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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.
}

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Code:

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#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);
}

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