// Event handler to handle a keyboard event.
// We use this function to accumulate characters typed into the console and build
// up the password this way.
// All event handler functions must return a boolean value indicating whether
// the password processing function should continue to read in another console
// input record (via ReadConsoleInput() API).
// Returning a true indicates continue.
// Returning a false indicates don't continue.
private bool KeyEventProc(INPUT_RECORD input_record, ref string strBuildup)
{
// From the INPUT_RECORD, extract the KEY_EVENT_RECORD structure.
KEY_EVENT_RECORD ker = input_record.Event.KeyEvent;
// We process only during the keydown event.
if (ker.bKeyDown != 0)
{
IntPtr intptr = new IntPtr(0); // This is to simulate a NULL handle value.
char ch = (char)(ker.uchar.UnicodeChar); // Get the current character pressed.
uint dwNumberOfCharsWritten = 0;
string strOutput = "*"; // The character string that will be displayed on the console screen.
// If we have received a Carriage Return character, we exit.
if (ch == (char)'\r')
{
return false;
}
else
{
if (ch > 0) // The typed in key must represent a character and must not be a control ley (e.g. SHIFT, ALT, CTRL, etc)
{
// A regular (non Carriage-Return character) is typed in...
// We first display a '*' on the screen...
WriteConsole
(
hStdout, // handle to screen buffer
strOutput, // write buffer
1, // number of characters to write
ref dwNumberOfCharsWritten, // number of characters written
intptr // reserved
);
// We build up our password string...
string strConcat = new string(ch, 1);
// by appending each typed in character at the end of strBuildup.
strBuildup += strConcat;
if (++iCounter < MaxNumberOfCharacters)
{
// Adding 1 to iCounter still makes iCounter less than MaxNumberOfCharacters.
// This means that the total number of characters collected so far (this is
// equal to iCounter, by the way) is less than MaxNumberOfCharacters.
// We can carry on.
return true;
}
else
{
// If, by adding 1 to iCounter makes iCounter greater than MaxNumberOfCharacters,
// it means that we have already collected MaxNumberOfCharacters number of characters
// inside strBuildup. We must exit now.
return false;
}
}
}
}
// The keydown state is false, we allow further characters to be typed in...
return true;
}
// All event handler functions must return a boolean value indicating whether
// the password processing function should continue to read in another console
// input record (via ReadConsoleInput() API).
// Returning a true indicates continue.
// Returning a false indicates don't continue.
private bool WindowBufferSizeEventProc(INPUT_RECORD input_record, ref string strBuildup)
{
// Since our Window Buffer Size Event Handler does not intend to do anything,
// we simply return a true to indicate to the password processing
// function to readin another console input record.
return true;
}
// The main function of this class.
public void PasswordInput(ref string refPasswordToBuild, int iMaxNumberOfCharactersSet)
{
INPUT_RECORD[] irInBuf = new INPUT_RECORD[128]; // Define an array of 128 INPUT_RECORD structs.
uint cNumRead = 0;
bool bContinueLoop = true; // Used to indicate whether to continue our ReadConsoleInput() loop.
// Reset character counter.
iCounter = 0;
// Initialize hStdin.
if (hStdin == (IntPtr)0)
{
hStdin = GetStdHandle(Constants.STD_INPUT_HANDLE);
if (hStdin == Constants.INVALID_HANDLE_VALUE)
{
return;
}
}
// Initialize hStdout.
if (hStdout == (IntPtr)0)
{
hStdout = GetStdHandle(Constants.STD_OUTPUT_HANDLE);
if (hStdout == Constants.INVALID_HANDLE_VALUE)
{
return;
}
}
// Retrieve the current console mode.
if (GetConsoleMode(hStdin, ref dwSaveOldMode) == false)
{
return;
}
// Set the current console mode to enable window input and mouse input.
// This is not necessary for our password processing application.
// This is set only for demonstration purposes.
//
// By setting ENABLE_WINDOW_INPUT into the console mode, user interactions
// that change the size of the console screen buffer are reported in the
// console's input buffer. Information about this event can be read from
// the input buffer by our application using the ReadConsoleInput function.
//
// By setting ENABLE_MOUSE_INPUT into the console mode, if the mouse pointer
// is within the borders of the console window and the window has the
// keyboard focus, mouse events generated by mouse movement and button presses
// are placed in the input buffer. Information about this event can be read from
// the input buffer by our application using the ReadConsoleInput function.
dwMode = Constants.ENABLE_WINDOW_INPUT | Constants.ENABLE_MOUSE_INPUT;
if (SetConsoleMode(hStdin, dwMode) == false)
{
return;
}
// To safeguard against invalid values, we stipulate that only if iMaxNumberOfCharactersSet
// is greater than zero do we set MaxNumberOfCharacters equal to it.
// Otherwise, MaxNumberOfCharacters is set to 20 by default.
// An alternative to setting MaxNumberOfCharacters to a default value is to throw an exception.
if (iMaxNumberOfCharactersSet > 0)
{
MaxNumberOfCharacters = iMaxNumberOfCharactersSet;
}
else
{
// We could throw an exception here if we want to.
MaxNumberOfCharacters = 20;
}
// Main loop to collect characters typed into the console.
while (bContinueLoop == true)
{
if
(
ReadConsoleInput
(
hStdin, // input buffer handle
irInBuf, // buffer to read into
128, // size of read buffer
out cNumRead // number of records read
) == true
)
{
// Dispatch the events to the appropriate handler.
for (uint i = 0; i < cNumRead; i++)
{
// Lookup the hashtable for the appropriate handler function... courtesy of Derek Kiong !
ConsoleInputEvent cie_handler = (ConsoleInputEvent)htCodeLookup[(object)(irInBuf[i].EventType)];
// Note well that htCodeLookup may not have the handler for the current event,
// so check first for a null value in cie_handler.
if (cie_handler != null)
{
// Invoke the handler.
bContinueLoop = cie_handler(irInBuf[i], ref refPasswordToBuild);
}
}
}
}
// Restore the previous mode before we exit.
SetConsoleMode(hStdin, dwSaveOldMode);
return;
}
