static public ulong Comp(ulong _maxVal, float _t, CompFunc _func)
{
if (_t > 1.0)
{
_t = 1.0f;
}
if (_t < 0)
{
_t = 0;
}
double val = (double)_func(_t) * (double)_maxVal;
return((ulong)val);
}
static public int Comp(int _maxVal, float _t, CompFunc _func)
{
if (_t > 1.0)
{
_t = 1.0f;
}
if (_t < 0)
{
_t = 0;
}
float val = _func(_t) * (float)_maxVal;
return((int)val);
}
/// <summary>
/// Compress the block buffer when it is full
/// The block buffer is made of literals and distance length pairs
/// </summary>
/// <param name="lastBlock">if set to <c>true</c> [last block].</param>
private void CompressBlockBuf(bool lastBlock)
{
// add end of block to code frequency array
_literalTree.CodeFreq[EndOfBlockSymbol]++;
// Build trees
_literalTree.BuildTree();
_distanceTree.BuildTree();
// Calculate bitlen frequency
int bitLengthExtraBits = _literalTree.CalcBLFreq(_bitLengthTree);
bitLengthExtraBits += _distanceTree.CalcBLFreq(_bitLengthTree);
// Build bitlen tree
_bitLengthTree.BuildTree();
// calculate length in bits of bit length tree
int blTreeCodes = _bitLengthTree.MaxUsedCodesBitLength();
// calculate total block length for dynamic coding
// The 17 is made of: 3 bits block header, 5 bits literal codes, 5 bits distance codes, 4 bits bit-length codes
int compressedLen = 17 + blTreeCodes * 3 + _bitLengthTree.GetEncodedLength() + bitLengthExtraBits +
_literalTree.GetEncodedLength() + _distanceTree.GetEncodedLength() + _blockBufExtraBits;
// compressed block length in bytes for dynamic coding
compressedLen = (compressedLen + 7) / 8;
// calculate total block length for static coding
int staticLen = 3 + _blockBufExtraBits;
for (int i = 0; i < MaxLiteralCodes; i++) staticLen += _literalTree.CodeFreq[i] * StaticLiteralLength[i];
for (int i = 0; i < MaxDistanceCodes; i++) staticLen += _distanceTree.CodeFreq[i] * StaticDistanceLength[i];
// static block length in bytes
staticLen = (staticLen + 7) / 8;
// static trees look better
if (staticLen <= compressedLen) compressedLen = staticLen;
// uncompressed read block length in bytes
int storedBlockLen = _readPtr - _readBlockStart;
// This is the last compressed block
if (lastBlock)
{
// If this this is the first block and the last block at the same time (relatively small file)
// and the uncompressed block is better than compressed block, change compression function from deflate to stored
if (_writeFirstBlock && storedBlockLen <= compressedLen)
{
CompFunction = CompFunc.Stored;
_readAvailableBytes = storedBlockLen;
DeflateStored();
return;
}
// Test compressed overall file length.
// If overall compressed length is more than the original uncompressed size
// the derived class will rewind the read and write stream.
if (WriteTotal + _writePtr + (_bitCount + 7) / 8 + Math.Min(compressedLen, storedBlockLen + 5) > ReadTotal)
{
// rewind both read and write streams
RewindStreams();
// read first block (the derived class will supply this routine)
_readAvailableBytes = ReadBytes(_readBuffer, 0, ReadBufSize, out _readEndOfFile);
// reset uncompressed and compressed totals
ReadTotal = (uint)_readAvailableBytes;
WriteTotal = 0;
// reset write ptr
_writePtr = 0;
_bitCount = 0;
// change compress function from deflate to stored
CompFunction = CompFunc.Stored;
// move input stream to output stream
DeflateStored();
return;
}
}
// Uncompressed block length is better than compressed length.
// Uncompressed block has 5 bytes overhead.
// Stored block header plus 2 bytes length and 2 bytes length complament.
if (storedBlockLen + 5 < compressedLen)
{
// loop in case block length is larger tan max allowed
while (storedBlockLen > 0)
{
// block length (max 65535)
int len = Math.Min(storedBlockLen, 0xffff);
// adjust remaing length
storedBlockLen -= len;
// Write the block on even byte boundry, Signal if this is the last block of the file
WriteStoredBlock(len, lastBlock && storedBlockLen == 0);
// adjust block start pointer
_readBlockStart += len;
}
}
// Encode with static tree
else if (compressedLen == staticLen)
{
// write static block header to output file
WriteBits(((int)BlockType.StaticTrees << 1) + (lastBlock ? 1 : 0), 3);
// replace the dynamic codes with static codes
_literalTree.SetStaticCodes(StaticLiteralCodes, StaticLiteralLength);
_distanceTree.SetStaticCodes(StaticDistanceCodes, StaticDistanceLength);
// Compress the block and send it to the output buffer
// This process converts the block buffer values into variable length sequence of bits.
CompressBlock();
// adjust block pointer
_readBlockStart += storedBlockLen;
}
// Encode with dynamic tree
else
{
// write dynamic block header to output file
WriteBits(((int)BlockType.DynamicTrees << 1) + (lastBlock ? 1 : 0), 3);
// write the dynamic tree to the output stream
SendAllTrees(blTreeCodes);
// Compress the block and send it to the output buffer
// This process converts the block buffer values into variable length sequence of bits.
CompressBlock();
// adjust block pointer
_readBlockStart += storedBlockLen;
}
// Set block buffer to empty
BlockReset();
// Reset write first block
_writeFirstBlock = false;
}
/// <summary>
/// Compress read stream to write stream
/// This is the main function of the DefaultMethod class
/// </summary>
protected void Compress()
{
// define compression control values based on the user compression level 0 to 9
CompFunction = CompFuncTable[_compLevel];
_goodLength = GoodLengthTable[_compLevel];
_maxLazyLength = MaxLazyTable[_compLevel];
_niceLength = NiceLengthTable[_compLevel];
_maxChainLength = MaxChainTable[_compLevel];
// read process initialization
_readBufferFilePosition = 0;
_readBlockStart = 0;
_readPtr = 0;
_readEndOfFile = false;
_matchStart = 0;
_matchLen = MinMatch - 1;
// read first block (the derived class will supply this routine)
_readBufEnd = ReadBytes(_readBuffer, 0, ReadBufSize, out _readEndOfFile);
ReadTotal = (uint)_readBufEnd;
// available bytes in the buffer
_readAvailableBytes = _readBufEnd;
// if file is less than 8 bytes, just store it
if (_readAvailableBytes < 8) CompFunction = CompFunc.Stored;
// write process initialization
WriteTotal = 0;
_writePtr = 0;
_bitBuffer = 0;
_bitCount = 0;
_writeFirstBlock = true;
// hash tables initialization
for (int hashPtr = _hashTable.Length - 1; hashPtr >= 0; hashPtr--) _hashTable[hashPtr] = -1;
for (int hashPtr = _hashPrevious.Length - 1; hashPtr >= 0; hashPtr--) _hashPrevious[hashPtr] = -1;
// switch based on the type of compression
switch (CompFunction)
{
case CompFunc.Stored:
DeflateStored();
break;
case CompFunc.Fast:
DeflateFast();
break;
case CompFunc.Slow:
DeflateSlow();
break;
}
// flush any left over bits in bit buffer
WriteAlignToByte();
if (_writePtr != 0)
{
WriteBytes(_writeBuffer, 0, _writePtr);
WriteTotal += (uint)_writePtr;
}
}
