public static int GetFrameSizeFromDataCount(MuComFrameDesc description, int dataCount)
{
if (description == MuComFrameDesc.ReadRequest)
{
return(2);
}
return((dataCount * 8 + 5) / 7 + 2);
}
public void ConstructorMustDecodeFrameProperly(byte[] inputBuffer, MuComFrameDesc desc, byte ID, byte[] dataBytes)
{
//Arrange
//Act
var frame = new MuComFrame(inputBuffer);
//Assert
frame.ID.Should().Be(ID);
frame.Description.Should().Be(desc);
frame.DataBytes.Should().Equal(dataBytes);
}
public MuComFrame(MuComFrameDesc description, byte ID, int dataCount, byte[] data)
{
if ((dataCount == 0) || (dataCount > 8))
{
throw new ArgumentException("Invalid dataCount '" + dataCount.ToString() + "'!");
}
this.Description = description;
this.ID = ID;
this.DataCount = dataCount;
this.RawBuffer = new byte[MuComFrame.GetFrameSizeFromDataCount(this.Description, this.DataCount)];
//Create first bytes with header and variable index
this.RawBuffer[0] = (byte)(0x80 | (int)this.Description | ((this.DataCount - 1) << 2) | (this.ID >> 6));
this.RawBuffer[1] = (byte)((this.ID << 1) & 0x7F);
//Handle read request differently
if (this.Description == MuComFrameDesc.ReadRequest)
{
this.DataBytes = new byte[0];
return;
}
//Copy data array
if (data is null)
{
throw new ArgumentNullException(nameof(data));
}
if (data.Length != dataCount)
{
throw new ArgumentException("Invalid length of array '" + nameof(data) + "'! " + data.Length.ToString() + " instead of " + dataCount.ToString() + "!");
}
this.DataBytes = data;
//Fill payload with data bytes
int payload_pos = 1;
int byte_pos = 0;
for (int data_pos = 0; data_pos < dataCount; data_pos++)
{
if (byte_pos < 0)
{
byte_pos = 6;
payload_pos++;
this.RawBuffer[payload_pos] = 0;
}
this.RawBuffer[payload_pos] |= (byte)(data[data_pos] >> (7 - byte_pos));
payload_pos++;
this.RawBuffer[payload_pos] = (byte)((data[data_pos] << byte_pos) & 0x7F);
byte_pos--;
}
}
public void ConstructorShouldConvertFineInBothDirections(MuComFrameDesc desc, byte ID, int dataCount, byte[] dataBytes)
{
//Arrange
var frameOne = new MuComFrame(desc, ID, dataCount, dataBytes);
//Act
var frameTwo = new MuComFrame(frameOne.RawBuffer);
//Assert
frameOne.Description.Should().Be(desc);
frameTwo.Description.Should().Be(desc);
frameOne.ID.Should().Be(ID);
frameTwo.ID.Should().Be(ID);
frameOne.DataCount.Should().Be(dataCount);
frameTwo.DataCount.Should().Be(dataCount);
frameOne.DataBytes.Should().Equal(dataBytes);
frameTwo.DataBytes.Should().Equal(dataBytes);
frameOne.RawBuffer.Should().Equal(frameTwo.RawBuffer);
}
public MuComFrame(byte[] inputBuffer)
{
if (inputBuffer is null)
{
throw new ArgumentNullException(nameof(inputBuffer));
}
if (inputBuffer.Length < 2)
{
throw new ArgumentException("Input buffer must contain at least two elements");
}
//Copy buffer
this.RawBuffer = new byte[inputBuffer.Length];
inputBuffer.CopyTo(this.RawBuffer, 0);
//Decode header
this.Description = MuComFrame.GetFrameDescriptionFromHeader(this.RawBuffer[0]);
this.ID = MuComFrame.GetIdFromFrame(this.RawBuffer);
this.DataCount = MuComFrame.GetDataByteCountFromHeader(this.RawBuffer[0]);
//A read request frame is only two bytes long and does not
if (this.Description == MuComFrameDesc.ReadRequest)
{
this.DataBytes = new byte[0];
return;
}
//Check input frame size
int expectedLength = MuComFrame.GetFrameSizeFromDataCount(this.Description, this.DataCount);
if (inputBuffer.Length < expectedLength)
{
throw new ArgumentException("Input buffer size too small! " + expectedLength.ToString() + " expected but input buffer contains only " + inputBuffer.Length.ToString() + " bytes.");
}
//Create buffer for data bytes and intermediate buffer
byte[] buffer = new byte[this.DataCount + 1];
this.DataBytes = new byte[this.DataCount];
//Reconstruct data from frame
//Buffer[0..8] = Data bytes (first byte will be index)
int dataPos = 0;
int bytePos = 1;
for (int i = 0; i < (this.DataBytes.Length + 1); i++)
{
if (bytePos < 0)
{
bytePos = 6;
dataPos++;
}
buffer[i] = (byte)(this.RawBuffer[dataPos] << (7 - bytePos));
dataPos++;
buffer[i] |= (byte)(this.RawBuffer[dataPos] >> bytePos);
bytePos--;
}
//Copy data
this.ID = buffer[0];
Array.Copy(buffer, 1, this.DataBytes, 0, this.DataBytes.Length);
}