size_t USBHIDKeyboard::pressRaw(uint8_t k) {
  uint8_t i;
  if (k >= 0xE0 && k < 0xE8) {
    // it's a modifier key
    _keyReport.modifiers |= (1 << (k - 0xE0));
  } else if (k && k < 0xA5) {
    // Add k to the key report only if it's not already present
    // and if there is an empty slot.
    if (_keyReport.keys[0] != k && _keyReport.keys[1] != k && _keyReport.keys[2] != k && _keyReport.keys[3] != k && _keyReport.keys[4] != k
        && _keyReport.keys[5] != k) {

      for (i = 0; i < 6; i++) {
        if (_keyReport.keys[i] == 0x00) {
          _keyReport.keys[i] = k;
          break;
        }
      }
      if (i == 6) {
        return 0;
      }
    }
  } else {
    //not a modifier and not a key
    return 0;
  }
  sendReport(&_keyReport);
  return 1;
}

size_t USBHIDKeyboard::releaseRaw(uint8_t k) {
  uint8_t i;
  if (k >= 0xE0 && k < 0xE8) {
    // it's a modifier key
    _keyReport.modifiers &= ~(1 << (k - 0xE0));
  } else if (k && k < 0xA5) {
    // Test the key report to see if k is present.  Clear it if it exists.
    // Check all positions in case the key is present more than once (which it shouldn't be)
    for (i = 0; i < 6; i++) {
      if (0 != k && _keyReport.keys[i] == k) {
        _keyReport.keys[i] = 0x00;
      }
    }
  } else {
    //not a modifier and not a key
    return 0;
  }

  sendReport(&_keyReport);
  return 1;
}

// press() adds the specified key (printing, non-printing, or modifier)
// to the persistent key report and sends the report.  Because of the way
// USB HID works, the host acts like the key remains pressed until we
// call release(), releaseAll(), or otherwise clear the report and resend.
size_t USBHIDKeyboard::press(uint8_t k) {
  if (k >= 0x88) {  // it's a non-printing key (not a modifier)
    k = k - 0x88;
  } else if (k >= 0x80) {  // it's a modifier key
    _keyReport.modifiers |= (1 << (k - 0x80));
    k = 0;
  } else {  // it's a printing key
    k = _asciimap[k];
    if (!k) {
      return 0;
    }
    if (k & 0x80) {  // it's a capital letter or other character reached with shift
      // At boot, some PCs need a separate report with the shift key down like a real keyboard.
      if (shiftKeyReports) {
        pressRaw(HID_KEY_SHIFT_LEFT);
      } else {
        _keyReport.modifiers |= 0x02;  // the left shift modifier
      }
      k &= 0x7F;
    }
  }
  return pressRaw(k);
}

// release() takes the specified key out of the persistent key report and
// sends the report.  This tells the OS the key is no longer pressed and that
// it shouldn't be repeated any more.
size_t USBHIDKeyboard::release(uint8_t k) {
  if (k >= 0x88) {  // it's a non-printing key (not a modifier)
    k = k - 0x88;
  } else if (k >= 0x80) {  // it's a modifier key
    _keyReport.modifiers &= ~(1 << (k - 0x80));
    k = 0;
  } else {  // it's a printing key
    k = _asciimap[k];
    if (!k) {
      return 0;
    }
    if (k & 0x80) {  // it's a capital letter or other character reached with shift
      if (shiftKeyReports) {
        releaseRaw(k & 0x7F);    // Release key without shift modifier
        k = HID_KEY_SHIFT_LEFT;  // Below, release shift modifier
      } else {
        _keyReport.modifiers &= ~(0x02);  // the left shift modifier
        k &= 0x7F;
      }
    }
  }
  return releaseRaw(k);
}