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 size) : Sine(frequency), mTableSize(size) {
    initWaveTable();
}

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

void WaveShaper::initWaveTable() {
    mTransferFunction.set_size(1, mTableSize);
    mTransferFunction.allocateBuffers();
    sample * sampPtr = mTransferFunction.monoBuffer(0);
    sample val = -1.0;
    sample incr = 2.0 / mTableSize;
    for (unsigned i = 0; i < mTableSize; i++) {
        *sampPtr++ = val;
        val += incr;
    }
                    // use this for a clipping wave shape
//#define clipit
#ifdef clipit
    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;
#endif
}

// The mono_next_buffer method does all the work

status WaveShaper::mono_next_buffer(Buffer & inputBuffer, Buffer & outputBuffer, unsigned inBufNum, unsigned outBufNum) {
                    // get the sine wave
    Sine::mono_next_buffer(inputBuffer, outputBuffer, inBufNum, outBufNum);
                    // get the pointers to the output buffer to write into
    sample * buffer = outputBuffer._monoBuffers[outBufNum];
    unsigned numFrames = outputBuffer._numFrames;
                    // get the pointer to the transfer function
    sample * function = mTransferFunction.mBuffers[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
    }
    return cslOk;
}