WaveShaper.cpp

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//
//  WaveShaper.h -- CSL wave-shaping oscillator class
//  See the copyright notice and acknowledgment of authors in the file COPYRIGHT
//

#include "WaveShaper.h"     // my superclass

using namespace csl;

// Trivial constructors

WaveShaper::WaveShaper() : Sine() {
    initWaveTable();
}

// Size is optional and defaults to 8192 bytes.

WaveShaper::WaveShaper(float frequency, unsigned sel, unsigned size) 
        : Sine(frequency), mTableSize(size) {
    initWaveTable(sel);
}

// initialize and fill in the default wavetable (a straight line)

void WaveShaper::initWaveTable(unsigned sel) {
    mTransferFunction.setSize(1, mTableSize);
    mTransferFunction.allocateBuffers();
    sample * sampPtr = mTransferFunction.buffer(0);
    sample val = -1.0;
    sample incr = 2.0 / mTableSize;
    switch (sel) {
    case 0:             // straight table
        for (unsigned i = 0; i < mTableSize; i++) {
            *sampPtr++ = val;
            val += incr;
        }
        break;
    case 1:             // use this for a clipping wave shape
        for (unsigned i = 0; i < mTableSize/6; i++)
            *sampPtr++ = -0.8333;
        for (unsigned i = mTableSize/6; i < 5*mTableSize/6; i++) {
            *sampPtr++ = val;
            val += incr;
        }
        for (unsigned i = 5*mTableSize/6; i < mTableSize; i++)
            *sampPtr++ = 0.8333;
        break;
    case 2:         // cube table
        for (unsigned i = 0; i < mTableSize; i++) {
            *sampPtr++ = val * val * val;
            val += incr;
        }
        break;
    case 3:         // other table
        for (unsigned i = 0; i < mTableSize/4; i++)
            *sampPtr++ = -0.5;
        for (unsigned i = mTableSize/4; i < 3*mTableSize/4; i++) {
            *sampPtr++ = val;
            val += incr;
        }
        for (unsigned i = 3*mTableSize/4; i < mTableSize; i++)
            *sampPtr++ = 0.5;   
        break;
    }
}

// The mono_next_buffer method does all the work

void WaveShaper::nextBuffer(Buffer & outputBuffer, unsigned outBufNum) throw (CException) {
                    // get the sine wave
    Sine::nextBuffer(outputBuffer, outBufNum);
                    // get the pointer to the output buffer to write into
    sample * buffer = outputBuffer.buffer(outBufNum);
    unsigned numFrames = outputBuffer.mNumFrames;
                    // get the pointer to the transfer function
    sample * function = mTransferFunction.buffer(0);
    unsigned fcnLength = mTransferFunction.mNumFrames;
    unsigned fcnLengthHalf = fcnLength / 2; 
    sample samp;

                    // now do the wave-shaping table look-up
    for (unsigned i = 0; i < numFrames; i++) {
        samp = *buffer;                                 // get a sample (assumed to be in the range +- 1.0)
        unsigned index = (samp + 1.0) * fcnLengthHalf;  // convert to a table index
        if (index < 0) index = 0;                       // make sure it's in the right range
        if (index >= fcnLength) index = fcnLength - 1;
        
        samp = function[index];                         // scale the sample
        *buffer++ = samp;                               // store it in the buffer
    }
}