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FTCharToGlyphIndexMap.h

#ifndef    __FTCharToGlyphIndexMap__
#define    __FTCharToGlyphIndexMap__

#include <stdlib.h>

#include "FTGL.h"

/**
 * Provides a non-STL alternative to the STL map<unsigned long, unsigned long>
 * which maps character codes to glyph indices inside FTCharmap.
 * 
 * Implementation:
 *   - NumberOfBuckets buckets are considered.
 *   - Each bucket has BucketSize entries.
 *   - When the glyph index for the character code C has to be stored, the 
 *     bucket this character belongs to is found using 'C div BucketSize'. 
 *     If this bucket has not been allocated yet, do it now.
 *     The entry in the bucked is found using 'C mod BucketSize'. 
 *     If it is set to IndexNotFound, then the glyph entry has not been set.
 *   - Try to mimic the calls made to the STL map API.
 *
 * Caveats:
 *   - The glyph index is now a signed long instead of unsigned long, so
 *     the special value IndexNotFound (= -1) can be used to specify that the 
 *     glyph index has not been stored yet.
 */
00027 class FTGL_EXPORT FTCharToGlyphIndexMap
{
    public:
  
        typedef unsigned long CharacterCode;
        typedef signed long GlyphIndex;
        
        enum 
        {
            NumberOfBuckets = 256,
            BucketSize = 256,
            IndexNotFound = -1
        };

        FTCharToGlyphIndexMap()
        {
            this->Indices = 0;
        }

        virtual ~FTCharToGlyphIndexMap()
        {
            if( this->Indices)
            {
                // Free all buckets
                this->clear();
        
                // Free main structure
                delete [] this->Indices;
                this->Indices = 0;
            }
        }
  
        void clear()
        {
            if(this->Indices)
            {
                for( int i = 0; i < FTCharToGlyphIndexMap::NumberOfBuckets; i++)
                {
                    if( this->Indices[i])
                    {
                        delete [] this->Indices[i];
                        this->Indices[i] = 0;
                    }
                }
            }
        }

        const GlyphIndex find( CharacterCode c)
        {
            if( !this->Indices)
            {
                return 0;
            }
        
            // Find position of char code in buckets
            div_t pos = div( c, FTCharToGlyphIndexMap::BucketSize);
        
            if( !this->Indices[pos.quot])
            {
                return 0;
            }
        
            const FTCharToGlyphIndexMap::GlyphIndex *ptr = &this->Indices[pos.quot][pos.rem];
            if( *ptr == FTCharToGlyphIndexMap::IndexNotFound)
            {
                return 0;
            }
        
            return *ptr;
        }

        void insert( CharacterCode c, GlyphIndex g)
        {
            if( !this->Indices)
            {
                this->Indices = new GlyphIndex* [FTCharToGlyphIndexMap::NumberOfBuckets];
                for( int i = 0; i < FTCharToGlyphIndexMap::NumberOfBuckets; i++)
                {
                    this->Indices[i] = 0;
                }
            }
        
            // Find position of char code in buckets
            div_t pos = div(c, FTCharToGlyphIndexMap::BucketSize);
        
            // Allocate bucket if does not exist yet
            if( !this->Indices[pos.quot])
            {
                this->Indices[pos.quot] = new GlyphIndex [FTCharToGlyphIndexMap::BucketSize];
                for( int i = 0; i < FTCharToGlyphIndexMap::BucketSize; i++)
                {
                    this->Indices[pos.quot][i] = FTCharToGlyphIndexMap::IndexNotFound;
                }
            }
          
            this->Indices[pos.quot][pos.rem] = g;
        }
  
    private:
        GlyphIndex** Indices;
};


#endif  //  __FTCharToGlyphIndexMap__

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