Clearing the data

#ifndef INC_KEYBOARD_H_#define INC_KEYBOARD_H_// Keyboard -- Defines an interface to a keyboard device.// (C)2003 David 'Redbeard' Eccleston//// Obtains input from a keyboard device.  Usually only one keyboard is present// on a system, and as such, only one instance of a keyboard object should be// created.//// Create a keyboard object with 'new', then call Init().  You can now request// keyboard data.  When a keyboard object is lost, it attempts to regain// itself anytime you request it to poll information.//// Usually, Poll() is called once per frame, before any keyboard data is// required.  After calling Poll(), the remaining functions can be used// to determine the state of the keys on the keyboard.//// IsPressed(key) - returns TRUE if the requested key (DirectInput keyboard// code) is currently pressed down.//// MakePressed(key) - can simulate a keypress that later code may act upon//// IsLatched(key) - returns TRUE if the key was pressed since the last time// the key's latch was cleared.  When a latch is cleared, the key is not// latched again until the key goes up, and is pressed down again.//// JustLatched(key) - returns TRUE is the key was latched on the last Poll()// call.  If you don't clear the latch, you can determine that the key wasn't // just pressed using this method.  Very odd, unsure when it would be useful,// but it was easy to support, so it's here.//// ReadAndClearLatch(key) - Reads the latch and clears it.  If no other parts// of your app will check the same latched key, this is useful in that you// won't have to make a second call to clear the latched key.//// ClearLatch() - Clears the latch of a key.  Allows you to determine the// next time the key is pressed, and to not think the key was pressed again// when it has been down for more than a single Poll() call.//// ClearAllLatches() - Clears the latches of all keys on the keyboard//// ClearAllLatchesAndKeysDown() - Stops any further keyboard activity until// the next poll.class Keyboard{public:  LPDIRECTINPUTDEVICE8  m_pKeyboard;  BYTE                  m_bKeyLatch[256];  BOOL Init();  void Poll();  BYTE IsPressed(int nKey) {return m_bKeyLatch[nKey] & 0x80;}  void MakePressed(BYTE nKey) {m_bKeyLatch[nKey] |= 0x80;}  BYTE IsLatched(int nKey) {return m_bKeyLatch[nKey] & 0x40;}  BYTE JustLatched(int nKey) {return m_bKeyLatch[nKey] & 0x20;}  BYTE ReadAndClearLatch(int nKey) {BYTE l = m_bKeyLatch[nKey]; m_bKeyLatch[nKey] &= ~0x40; return l&0x40;}  void ClearLatch(int nKey) {m_bKeyLatch[nKey] &= ~0x40;}  void ClearAllLatches();  void ClearAllLatchesAndKeysDown();  Keyboard();  ~Keyboard();};#endif

#include "stdafx.h"#include "engine3d.h"#include "keyboard.h"#include "main.h"Keyboard::Keyboard(){  m_pKeyboard = 0;}Keyboard::~Keyboard(){  if (m_pKeyboard)  {    m_pKeyboard->Unacquire();    m_pKeyboard->Release();  }}void Keyboard::ClearAllLatches(){  DWORD *l, n;  n = 256/4;  l = (DWORD *)m_bKeyLatch;  while (n--)  {    *l &= ~0x40404040;    l++;  }}void Keyboard::ClearAllLatchesAndKeysDown(){  memset(m_bKeyLatch, 0, sizeof(m_bKeyLatch));}BOOL Keyboard::Init(){  HRESULT hr;  ClearAllLatchesAndKeysDown();  if( FAILED( hr = g_Engine3D->m_pDInput->CreateDevice( GUID_SysKeyboard, &m_pKeyboard, NULL ) ) )  {    g_Errors.Add("Create keyboard");    g_Errors.Add((char *)DXGetErrorString9(hr));    return FALSE;  }  // This tells DirectInput that we will be passing an array  // of 256 bytes to IDirectInputDevice::GetDeviceState.  if( FAILED( hr = m_pKeyboard->SetDataFormat( &c_dfDIKeyboard ) ) )  {    g_Errors.Add("Set keyboard format");    g_Errors.Add((char *)DXGetErrorString9(hr));    return FALSE;  }  if (FAILED(hr = m_pKeyboard->SetCooperativeLevel( g_pDefaultEngineWindow->m_d3dpp.hDeviceWindow, DISCL_NONEXCLUSIVE | DISCL_FOREGROUND )))  {    g_Errors.Add("Set keyboard cooperative level ");    g_Errors.Add((char *)DXGetErrorString9(hr));    return FALSE;  }  m_pKeyboard->Acquire();  return TRUE;}void Keyboard::Poll(){  HRESULT hr;  int n;  DWORD *down, *latch, d, l;  BYTE bKeys[256];  hr = m_pKeyboard->GetDeviceState(256, bKeys);  if (FAILED(hr))  {    // We'll get a 1 frame lag on re-acquiring the keyboard, but hey, not a big deal.    // Attempt to reacquire, and return so we don't use the uninitialized key states.    hr = m_pKeyboard->Acquire();    return;  }  // Now handle latched and just latched, and copy keydowns  n = 256/4;  down = (DWORD *)bKeys;  latch = (DWORD *)m_bKeyLatch;  while (n--)  {    d = *down & 0x80808080;   // Only look at the down flag    l = *latch & 0xC0C0C0C0;  // Keep previous down keys, and latches, but clear just latched    // Remember current set of down keys, keep previous uncleared latches,    // and add any keys that are newly down to both latch and just latched.    *latch = d | (l & 0x40404040) | ((d&(~l))>>1) | ((d&(~l))>>2);    down++;    latch++;  }}#if 0// Test sample app - all 3 methods of interpreting keysvoid Init(){  g_pKeyboard = new Keyboard();  if (!g_pKeyboard)    return E_FAIL;  if (!g_pKeyboard->Init())    return E_FAIL;}void Cleanup(){  if (g_pKeyboard)    delete g_pKeyboard;  g_pKeyboard = 0;}void ReadKeys(){  static float x=0, y=0;  static int mode=0;  g_Keyboard->Poll();  if (g_pKeyboard->IsLatched(DIK_T))  {    mode = (mode+1)%3;    g_pKeyboard->ClearAllLatches();  }  if (mode==0)  {    if (g_pKeyboard->IsPressed(DIK_UP))      y -= 1;    if (g_pKeyboard->IsPressed(DIK_DOWN))      y += 1;    if (g_pKeyboard->IsPressed(DIK_LEFT))      x -= 1;    if (g_pKeyboard->IsPressed(DIK_RIGHT))      x += 1;  }  else if (mode==1)  {    if (g_pKeyboard->IsLatched(DIK_UP))    {      y -= 5;      g_pKeyboard->ClearLatch(DIK_UP);    }    if (g_pKeyboard->IsLatched(DIK_DOWN))    {      y += 5;      g_pKeyboard->ClearLatch(DIK_DOWN);    }    if (g_pKeyboard->IsLatched(DIK_LEFT))    {      x -= 5;      g_pKeyboard->ClearLatch(DIK_LEFT);    }    if (g_pKeyboard->IsLatched(DIK_RIGHT))    {      x += 5;      g_pKeyboard->ClearLatch(DIK_RIGHT);    }  }  else if (mode==2)  {    if (g_pKeyboard->JustLatched(DIK_UP))      y -= 5;    if (g_pKeyboard->JustLatched(DIK_DOWN))      y += 5;    if (g_pKeyboard->JustLatched(DIK_LEFT))      x -= 5;    if (g_pKeyboard->JustLatched(DIK_RIGHT))      x += 5;  }}#endif