public static UsbPacket CreateUSBPacketFromByteArray(byte[] byteArray)
{
uint offset = 0;
UsbPacket usbPacket = new UsbPacket();
usbPacket.packetType = (UsbPacketType)byteArray[offset];
offset = offset + 1;
usbPacket.reserved1 = byteArray[offset];
offset = offset + 1;
usbPacket.reserved2 = BitConverter.ToInt16(byteArray, (int)offset);
offset = offset + 2;
usbPacket.packetId = BitConverter.ToInt16(byteArray, (int)offset);
offset = offset + 2;
usbPacket.reserved3 = BitConverter.ToInt16(byteArray, (int)offset);
offset = offset + 2;
usbPacket.dataSize = BitConverter.ToInt32(byteArray, (int)offset);
offset = offset + 4;
usbPacket.data = new byte[usbPacket.dataSize];
try
{
Array.Copy(byteArray, offset, usbPacket.data, 0, usbPacket.dataSize);
}
catch (ArgumentException)
{
File.AppendAllText(Path.Combine(Assembly.GetExecutingAssembly().Location, "bad-packets.txt"), BitConverter.ToString(byteArray));
Console.Error.WriteLine("Skipped bad packet");
usbPacket.packetId = -1;
}
return(usbPacket);
}
public static void CreateUSBPacketByteArray(UsbPacket usbPacket, ref byte[] destinationArray)
{
CreateUSBPacketByteArray(usbPacket.packetType, usbPacket.packetId, usbPacket.dataSize, usbPacket.data, ref destinationArray);
}
public void GarminWrite(UsbPacket usbPacket)
{
//TODO: Place this check ouside this method to make sure that multiple write calls are made if
//data size is greater than MAX_BUFFER_SIZE
/*
* the size of all the data sent to the device is the size of the
* usb data structure(3.2.2) plus the size of all the data sent (index 12+ of the structure)
*/
int theBytesToWrite = Marshal.SizeOf(usbPacket) + usbPacket.dataSize;
int theBytesReturned = 0;
// prepare and format the data to be sent
byte[] dataAsArray = null;
Utilities.CreateUSBPacketByteArray(usbPacket, ref dataAsArray);
GCHandle gcDataHandle = GCHandle.Alloc(dataAsArray, GCHandleType.Pinned);
IntPtr gcDataHandleAddress = gcDataHandle.AddrOfPinnedObject();
// prepare a destination address for the data to be written
GCHandle gcReturnDataHandle = GCHandle.Alloc(theBytesReturned, GCHandleType.Pinned);
IntPtr gcReturnDataHandleAddress = gcReturnDataHandle.AddrOfPinnedObject();
try
{
bool success = UnsafeNativeMethods.WriteFile(
Handle,
gcDataHandleAddress,
theBytesToWrite,
gcReturnDataHandleAddress,
new Overlapped());
// format the data written at the addresses in a .net readable structure
int returnedBytes = (int)Marshal.PtrToStructure(gcReturnDataHandleAddress, typeof(Int32));
if (success == false || returnedBytes != theBytesToWrite)
{
throw new InvalidOperationException("UnableToWriteToDevice");
}
// If the packet size was an exact multiple of the USB packet
// size, we must make a final write call with no data (3.2.3.1)
if (theBytesToWrite % PacketSize == 0)
{
success = UnsafeNativeMethods.WriteFile(
Handle,
IntPtr.Zero,
0,
gcReturnDataHandleAddress,
new Overlapped());
}
if (success == false)
{
throw new InvalidOperationException("Unable to write to device");
}
}
finally
{
gcDataHandleAddress = IntPtr.Zero;
gcReturnDataHandleAddress = IntPtr.Zero;
gcDataHandle.Free();
gcReturnDataHandle.Free();
}
}
