/// <summary>
/// Calculates a set of transformations that reads reduced byte variable of size 'bits' shifted by 'bitOffset'.
/// </summary>
/// <returns>Set of byte transformations.</returns>
/// <param name="bits">Number of bits of input data.</param>
/// <param name="bitOffset">Number of bits by which input data is shifted.</param>
private static TransformationDescriptor[] ByteInflate(byte bits, byte bitOffset)
{
if (bits == 0 || bits > 8)
{
throw new ArgumentOutOfRangeException("bits");
}
if (bitOffset > 7)
{
throw new ArgumentOutOfRangeException("bitOffset");
}
var result = new List <TransformationDescriptor>();
var bitsLeft = bits;
var additionalShift = 0;
while (bitsLeft > 0)
{
var currentBits = (byte)Math.Min(8 - bitOffset, bitsLeft);
var mask = ((1 << currentBits) - 1) << (8 - bitOffset - currentBits);
var shift = (sbyte)(-bitOffset + additionalShift);
// optimization
if ((mask >> shift) == (0xFF >> shift))
{
mask = 0xFF;
}
var descriptor = new TransformationDescriptor(shift, (byte)mask, currentBits);
result.Add(descriptor);
bitOffset = 0;
additionalShift += currentBits;
bitsLeft -= currentBits;
}
return(result.ToArray());
}
/// <summary>
/// Calculates a set of transformations that reads reduced byte variable of size 'bits' shifted by 'bitOffset'.
/// </summary>
/// <returns>Set of byte transformations.</returns>
/// <param name="bits">Number of bits of input data.</param>
/// <param name="bitOffset">Number of bits by which input data is shifted.</param>
private static TransformationDescriptor[] ByteInflate(byte bits, byte bitOffset)
{
if(bits == 0 || bits > 8)
{
throw new ArgumentOutOfRangeException("bits");
}
if(bitOffset > 7)
{
throw new ArgumentOutOfRangeException("bitOffset");
}
var result = new List<TransformationDescriptor>();
var bitsLeft = bits;
var additionalShift = 0;
while(bitsLeft > 0)
{
var currentBits = (byte)Math.Min(8 - bitOffset, bitsLeft);
var mask = ((1 << currentBits) - 1) << (8 - bitOffset - currentBits);
var shift = (sbyte)(-bitOffset + additionalShift);
// optimization
if ((mask >> shift) == (0xFF >> shift))
{
mask = 0xFF;
}
var descriptor = new TransformationDescriptor(shift, (byte)mask, currentBits);
result.Add(descriptor);
bitOffset = 0;
additionalShift += currentBits;
bitsLeft -= currentBits;
}
return result.ToArray();
}
