/// <summary>
/// Takes source bits, starting at the given MSB-0 bit index, and merges it into the given destination byte,
/// at the given destination MSB-0 bit index.
/// </summary>
/// <param name="sourceByte">The source bits that will be merged with the destination bits.</param>
/// <param name="sourceMsbIndex">The MSB-0 index into the <paramref name="sourceByte"/>, which is the
/// starting index of the bits to be merged; MSB-0 index 7 (which is the LSB) is the ending index.</param>
/// <param name="destinationByte">The other group of bits that will be merged with the source bits.</param>
/// <param name="destinationLsbIndex">The MSB-0 index into the <paramref name="destinationByte"/>, which
/// is the <i>ending</i> index of the bits to be merged; MSB-0 index 0 (which is the MSB) is the starting
/// index.</param>
/// <param name="maskUtilities">An injected object which implements the <see cref="IBitMaskUtilities"/>
/// interface.</param>
/// <returns>The two bytes, blended together, at their given offsets.</returns>
public byte AlignAndMergeBytes(byte sourceByte, int sourceMsbIndex, byte destinationByte,
int destinationLsbIndex, IBitMaskUtilities maskUtilities)
{
const byte byteMaskToTruncateLeftBits = 0xFF;
var sourceByteMask = (byte)~maskUtilities.GetByteMsbMask(sourceMsbIndex);
var destinationByteMask = maskUtilities.GetByteMsbMask(destinationLsbIndex + 1);
sourceByte &= sourceByteMask;
var deltaShiftAmount = destinationLsbIndex - sourceMsbIndex + 1;
if (deltaShiftAmount < 0)
{
sourceByte = (byte)((sourceByte << -deltaShiftAmount) & byteMaskToTruncateLeftBits);
}
else
{
sourceByte = (byte)(sourceByte >> deltaShiftAmount);
}
return (byte)(destinationByte & destinationByteMask | sourceByte);
}
[TestCase(8, 0b11111111)] // 0xFF
public void ShouldGetByteMsbMask(int numBitsToMask, byte expectedMask)
{
var actualMask = bmu.GetByteMsbMask(numBitsToMask);
Assert.That(actualMask, Is.EqualTo(expectedMask));
}
public byte GetByteMsbMask(int numBitsToMask) => bitMaskUtilities.GetByteMsbMask(numBitsToMask);