SampleHuffman.h

/*
 * SampleHuffman.h
 *
 * This file is part of Mozzi.
 *
 * Copyright 2013-2024 Tim Barrass and the Mozzi Team
 *
 * Mozzi is licensed under the GNU Lesser General Public Licence (LGPL) Version 2.1 or later.
 *
 */
 
#ifndef SAMPLEHUFFMAN_H
#define SAMPLEHUFFMAN_H
 
#include "mozzi_pgmspace.h"
 
class SampleHuffman
{
 
public:
 
    SampleHuffman(uint8_t const * SOUNDDATA, int16_t const * HUFFMAN_DATA, uint32_t const SOUNDDATA_BITS):sounddata(SOUNDDATA),huffman(HUFFMAN_DATA),sounddata_bits(SOUNDDATA_BITS)
    {
        setLoopingOff();
    }
 
 
    inline
    int16_t next()
    {
        if(datapos >= sounddata_bits){
            if(looping){
                // at end of sample, restart from zero, looping the sound
                 datapos = 0;
            }else{
                return 0;
            }
        }
        
        int16_t dif = decode();
        current += dif; // add differential
        return current;
    }
 
 
    inline
    void setLoopingOn()
    {
        looping=true;
    }
 
 
    inline
    void setLoopingOff()
    {
        looping=false;
    }
 
    inline
    void start()
    {
        current = 0;
        datapos = 0;
        bt = 0;
    }
    
private:
    uint8_t const * sounddata;
    int16_t const * huffman;
    uint32_t const sounddata_bits;
    uint32_t datapos; // current sample position
    int16_t current; // current amplitude value
    bool looping;
    uint8_t bt;
    
    // Get one bit from sound data
    inline 
    bool getbit()
    {
        const uint8_t b = datapos&7;
        //static uint8_t bt;
        if(!b) bt = FLASH_OR_RAM_READ<const uint8_t>(sounddata+((uint32_t)datapos>>3));
        // extract the indexed bit
        return ((uint8_t)bt>>(7-b))&1;
    }
 
 
    // Decode bit stream using Huffman codes
    inline
    int16_t decode()
    {
        int16_t const * huffcode = huffman;
        do {
            if(getbit()) {
                const int16_t offs = FLASH_OR_RAM_READ<const int16_t>(huffcode);
                huffcode += offs?offs+1:2;
            }
            datapos++;
        }
        while(FLASH_OR_RAM_READ<const int16_t>(huffcode++));
        return FLASH_OR_RAM_READ<const int16_t>(huffcode);
    }
 
 
};
 
#endif        //  #ifndef SAMPLEHUFFMAN_H