/// <summary>
/// Calculates the metadata from the given values
/// </summary>
/// <param name="values"></param>
/// <returns></returns>
public static BlockyMetadata FromData(List <OfcNumber> values)
{
if (values.Count == 0)
{
throw new InvalidOperationException("Cannot gather compression metadata with 0 values!");
}
var metadata = new BlockyMetadata()
{
IsNegative = values.First().IsNegative, IsAbsolute = true, ValueCount = values.Count
};
foreach (var ofcNumber in values)
{
if (ofcNumber.NeededBitsNumber > metadata.MaxNeededBitsNumber)
{
metadata.MaxNeededBitsNumber = ofcNumber.NeededBitsNumber;
metadata.LargestPossibleValue = Utility.GetMaxValue(ofcNumber.NeededBitsNumber);
}
if (ofcNumber.NeededBitsExponent > metadata.MaxNeededBitsExponent)
{
metadata.MaxNeededBitsExponent = ofcNumber.NeededBitsExponent; //Todo: this is redundant af, we should be able to calculate it from the huffman creator
}
if (metadata.IsAbsolute && ofcNumber.IsNegative != metadata.IsNegative)
{
metadata.IsAbsolute = false;
}
if (metadata.NoExponent && ofcNumber.Exponent != 0)
{
metadata.NoExponent = false;
}
}
return(metadata);
}
protected BlockyDecompression([NotNull] Stream reader)
{
_bitReader = new StreamBitReader(reader);
Metadata = BlockyMetadata.FromBitStream(_bitReader);
_decompressionMethods[(int)Blockfinding.Blockfinding.Methods.PatternSame] = new PatternSameDecompression(Metadata);
_decompressionMethods[(int)Blockfinding.Blockfinding.Methods.PatternPingPong] = new PatternPingPongDecompression(Metadata);
_decompressionMethods[(int)Blockfinding.Blockfinding.Methods.FloatSimmilar] = new FloatSimmilarDecompression(Metadata);
_decompressionMethods[(int)Blockfinding.Blockfinding.Methods.NumbersNoExp] = new NumbersNoExpDecompression(Metadata);
_decompressionMethods[(int)Blockfinding.Blockfinding.Methods.PatternOffset] = new PatternOffsetDecompression(Metadata);
if (_bitReader.ReadByte(1) > 0) // use huffman
{
throw new NotImplementedException();
}
}
/// <summary>
/// Reads the metadata in its binary form
/// </summary>
/// <param name="reader"></param>
/// <returns></returns>
public static BlockyMetadata FromBitStream(StreamBitReader reader)
{
var metadata = new BlockyMetadata {
ValueCount = (int)reader.Read(31)
};
// ReSharper disable once AssignmentInConditionalExpression
if (metadata.IsAbsolute = reader.ReadByte(1) > 0)
{
metadata.IsNegative = reader.ReadByte(1) > 0;
}
metadata.MaxNeededBitsExponent = reader.ReadByte(4);
metadata.MaxNeededBitsNumber = reader.ReadByte(6);
metadata.MaxNeededBitsNeededBitsNumber = Utility.GetNeededBits(metadata.MaxNeededBitsNumber);
metadata.LargestPossibleValue = Utility.GetMaxValue(metadata.MaxNeededBitsNumber);
return(metadata);
}
/// <summary>
/// Will calculate everything and make it ready for writing
/// </summary>
public void Finish()
{
if (Values.Count == 0)
{
return;
}
Metadata = BlockyMetadata.FromData(Values);
Metadata.MaxNeededBitsNeededBitsNumber = Utility.GetNeededBits(Metadata.MaxNeededBitsNumber);
_blockfinding = new Blockfinding.Blockfinding(Values, Metadata);
Blocks = _blockfinding.FindAllBlocks();
PostCompressionOptimisation(); //Todo: make optional
Write();
}
/// <remarks>This will set OverrideGlobalNb but not the NeededBits</remarks>
/// <param name="metadata"></param>
/// <param name="newNb"></param>
/// <returns>The bit difference that would occur when changing the NeededBits in the header to newNb</returns>
public int DifferenceWithNb(BlockyMetadata metadata, ref byte newNb) //Bug: wrong calculatons if nb > maxNb ?
{
if (metadata.MaxNeededBitsNeededBitsNumber < (metadata.MaxNeededBitsNumber - newNb) * Length) // If the space we'd save in the header by not overriding the nb is smaller than the space we'd save at the values because of the overriden nb # TL;DR: If it's worth to override the nb in the header
{
if (!OverrideGlobalNb)
{
OverrideGlobalNb = true;
return((NeededBits - newNb) * Length - metadata.MaxNeededBitsNeededBitsNumber); // The bits we'll save with the header change - the bits we'll waste by overriding the nb in the header (adds some overhead ...)
}
}
else if (OverrideGlobalNb) // If the nb are overriden but it's not worth to override them (which is why we got to 'else' ...)
{
OverrideGlobalNb = false;
newNb = metadata.MaxNeededBitsNumber; // Bug: moved this from the if above. Not sure if i have missed something or fixed a bug :S
return((NeededBits - newNb) * Length + metadata.MaxNeededBitsNeededBitsNumber); // The bits we'll save with the header change + the bits we'll save by not overriding the nb in the header (removes some overhead ...)
}
return((NeededBits - newNb) * Length); // the bits we'll save if the nb were already overriden and have changed value
}
public bool ShouldOverrideNb(BlockyMetadata metadata)
{
return(metadata.MaxNeededBitsNeededBitsNumber < (metadata.MaxNeededBitsNumber - NeededBits) * Length && !HasPattern);
}
