Octane v1.01.20 - The Open Compression Toolkit for C++

http://octane.sourceforge.net/

coders/coder_huffman/huffmannodes.cpp

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//---------------------------------------------------------------------------

//---------------------------------------------------------------------------
// application includes
#include "huffmannodes.hpp"
// system includes
using namespace std;
//---------------------------------------------------------------------------



//---------------------------------------------------------------------------
// The traverse_buildbitcodes member function is recursively compute bitcodes for each leaf; it will code entire tree if called on the root.
void HuffNode::traverse_buildbitcodes(bitset<DEF_HUFFMANPQ_MAXFUNCBITS> &current_bitset, int bitsetlength)
{
        // only the derived versions of this virtual function should ever be called.
        cout << " error -> HuffNode::traverse_buildbitcodes should not be called." << endl;
}

void HuffNode_Middle::traverse_buildbitcodes(bitset<DEF_HUFFMANPQ_MAXFUNCBITS> &current_bitset, int bitsetlength)
{
        // traverse_buildbitcodes left tree
        if (bitsetlength>DEF_HUFFMANPQ_MAXIMUM_CODEBITDEPTH)
                {
                // we allow for the possibility that some initially built symbols will have a bitdepth which is too long for the dictionary
                //  such symbols must be removed prior during pruning (note we record above the real bitdepth, but here only copy the limit)
                // we comment this out here (the warning will still be shown when listing symbolset)
                bitsetlength=DEF_HUFFMANPQ_MAXIMUM_CODEBITDEPTH;
                }
        current_bitset[bitsetlength]=false;
        child0->traverse_buildbitcodes(current_bitset,bitsetlength+1);
        // traverse_buildbitcodes right tree
        current_bitset[bitsetlength]=true;
        child1->traverse_buildbitcodes(current_bitset,bitsetlength+1);
}

void HuffNode_Leaf::traverse_buildbitcodes(bitset<DEF_HUFFMANPQ_MAXFUNCBITS> &current_bitset, int bitsetlength)
{
        // set bits used to code this symbol (the DEF_HUFFMANPQ_MAXFUNCBITS is just an insanely large number of bits which doesn't affect memory usage)
        int count, length;
        // first store the bitset in the leaf
        code_bitsetlength=bitsetlength;
        length=bitsetlength;
        if (length>DEF_HUFFMANPQ_MAXIMUM_CODEBITDEPTH)
                {
                // we allow for the possibility that some initially built symbols will have a bitdepth which is too long for the dictionary
                //  such symbols must be removed prior during pruning (note we record above the real bitdepth, but here only copy the limit)
                // we comment this out here (the warning will still be shown when listing symbolset)
                length=DEF_HUFFMANPQ_MAXIMUM_CODEBITDEPTH;
                }
        // copy the bitset
        for (count=0;count<length;++count)
                code_bitset[count]=current_bitset[count];
}
//---------------------------------------------------------------------------


//---------------------------------------------------------------------------
string HuffNode_Leaf::get_bitcode_string()
{
        // return the bitcode in nice string, for debugging
        string bitset_string;
        int count;

        // don't try to read more than we actually stored
        int length=code_bitsetlength;
        if (length>DEF_HUFFMANPQ_MAXIMUM_CODEBITDEPTH)
                length=DEF_HUFFMANPQ_MAXIMUM_CODEBITDEPTH;

        for (count=0;count<length;++count)
                {
                if (code_bitset[count]==false)
                        bitset_string+="0";
                else
                        bitset_string+="1";
                }

        // add a note if its truncated (and thus unusable)
        if (code_bitsetlength>length)
                {
                char dummystr[80];
                sprintf(dummystr," (only %d of %d bits stored; symbol unuseable).",length,code_bitsetlength);
                bitset_string+=dummystr;
                }

        // return bits as string
        return bitset_string;
}
//---------------------------------------------------------------------------


//---------------------------------------------------------------------------
bool HuffNode_Leaf::AddBitsToBitWriter(bitwriter &bw)
{
        // push the bits from this code into the bitset
        // protect against too many bits
        int length=code_bitsetlength;
        if (length>DEF_HUFFMANPQ_MAXIMUM_CODEBITDEPTH)
                {
                // this is an error - it means we get a symbol whose bitcode we didn't store fully
                return false;
                }

        // add bits
        for (int count=0;count<length;++count)
                bw.put_bit(code_bitset[count]);
                
        // return success
        return true;
}
//---------------------------------------------------------------------------

 

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