code conservation.

maFiltah.c

#include "../MachineInterface.h"
#include <windows.h>
#include <math.h>
#include <float.h>

#pragma optimize ("awy", on) 

CMachineParameter const paraCutoff =
{
    pt_word,                 // Parameter data type
    "Cutoff",                // Parameter name as its shown in the parameter window
    "Filter Cutoff",         // Parameter description as its shown in the pattern view's statusbar
    0,                       // Minimum value
    22050,                   // Maximum value
    0xFFFF,                  // Novalue, this value means "nothing happened" in the mi::Tick procedure
    MPF_STATE,               // Parameter options, MPF_STATE makes it appears as a slider
    22050                    // the default slider value
};

CMachineParameter const paraResonance =
{
    pt_byte,                 // Parameter data type
    "Resonance",             // Parameter name as its shown in the parameter window
    "Filter Resonance",      // Parameter description as its shown in the pattern view's statusbar
    1,                       // Minimum value
    0xFE,                    // Maximum value
    0xFF,                    // Novalue, this value means "nothing happened" in the mi::Tick procedure
    MPF_STATE,               // Parameter options, MPF_STATE makes it appears as a slider
    0x0                      // the default slider value
};

CMachineParameter const *pParameters[] = {
    &paraCutoff,
    &paraResonance
};

CMachineAttribute const *pAttributes[] = { NULL };

#pragma pack(1)                        

class gvals
{
  public:
    word cutoff;
    byte resonance;
};

#pragma pack()

CMachineInfo const MacInfo = 
{
    MT_EFFECT,                 // Machine type
    MI_VERSION,                // Machine interface version
    MIF_DOES_INPUT_MIXING,     // Machine flags
    0,                         // min tracks
    0,                         // max tracks
    2,                         // numGlobalParameters
    0,                         // numTrackParameters
    pParameters,               // pointer to parameter stuff
    0,                         // numAttributes
    pAttributes,               // pointer to attribute stuff
    "Ome PFilter",             // Full Machine Name
    "PFilter",                 // Short name
    "A BuzzDev Ex.",           // Author name
    "&About..."                // Right click menu commands
};


class miex : public CMachineInterfaceEx { };

class mi : public CMachineInterface
{
public:
    mi();
    virtual ~mi();
    virtual void Tick();
    virtual void Init(CMachineDataInput * const pi);
    virtual bool Work(float *psamples, int numsamples, int const mode);
    virtual bool WorkMonoToStereo(float *psamples, int numsamples, int const mode);
    virtual void Command(int const i);
    virtual void Save(CMachineDataOutput * const po);
    virtual char const *DescribeValue(int const param, int const value);
    virtual CMachineInterfaceEx *GetEx() { return &ex; }
    virtual void OutputModeChanged(bool stereo) {}

    // Ma filtah here:
    virtual void MaFiltah();

public:
    miex ex;

public:
    // Filter stuff
    float param_cutoff, param_resonance;
    float filtCoefTab[5];
    float lx1, lx2, ly1, ly2; // Left sample history
    float rx1, rx2, ry1, ry2; // Right sample history

    gvals gval;
};

mi::mi() {  GlobalVals = &gval; }
mi::~mi() { }

void mi::MaFiltah () {
    float alpha, omega, sn, cs;
    float a0, a1, a2, b0, b1, b2;

    // These limits the cutoff frequency and resonance to
    // reasoneable values.
    if (param_cutoff < 20.0f) { param_cutoff = 20.0f; };
    if (param_cutoff > 22000.0f) { param_cutoff = 22000.0f; };
    if (param_resonance < 1.0f) { param_resonance = 1.0f; };
    if (param_resonance > 127.0f) { param_resonance = 127.0f; };

    omega = 2.0f * PI * param_cutoff/pMasterInfo->SamplesPerSec;
    sn = sin (omega); cs = cos (omega);
    alpha = sn / param_resonance;
    b0 = (1.0f - cs) / 2.0f;
    b1 = 1.0f - cs;
    b2 = (1.0f - cs) / 2.0f;
    a0 = 1.0f + alpha;
    a1 = -2.0f * cs;
    a2 = 1.0f - alpha;
    filtCoefTab[0] = b0/a0;
    filtCoefTab[1] = b1/a0;
    filtCoefTab[2] = b2/a0;
    filtCoefTab[3] = -a1/a0;
    filtCoefTab[4] = -a2/a0;
}

void mi::Init(CMachineDataInput * const pi)
{
    pCB->SetnumOutputChannels(pCB->GetThisMachine(), 2);
    pCB->SetMachineInterfaceEx((CMachineInterfaceEx *)&ex);
    param_cutoff = 22050;
    param_resonance = 0;
    MaFiltah ();
    lx1 = lx2 = ly1 = ly2 = 0.0f;
    rx1 = rx2 = ry1 = ry2 = 0.0f;
}

void mi::Save(CMachineDataOutput * const po) { }

void mi::Tick() {
    if (gval.cutoff != 0xFFFF) {
          param_cutoff = (float)gval.cutoff;
          MaFiltah();
    };
    if (gval.resonance != 0xFF) { 
          param_resonance = ((float)gval.resonance / 2.0f); 
          MaFiltah(); 
    };
}

bool mi::Work(float *psamples, int numsamples, int const mode)
{
    return false;
}

bool mi::WorkMonoToStereo(float *psamples, int numsamples, int const mode)
{
    if (mode==WM_WRITE)
        return false;
    if (mode==WM_NOIO)
        return false;
    if (mode==WM_READ)                        // <thru>
        return true;

    float inL, inR, outL, outR, temp_y;
    int i;

    for( i=0; i<numsamples*2; i++ ) {

        inL = psamples[i];
        inR = psamples[i+1];

        outL = inL;
        outR = inR;

        // Left
        temp_y = filtCoefTab[0] * outL +
                 filtCoefTab[1] * lx1 +
                 filtCoefTab[2] * lx2 +
                 filtCoefTab[3] * ly1 +
                 filtCoefTab[4] * ly2;
        ly2 = ly1; ly1 = temp_y; lx2 = lx1; lx1 = outL ; outL = temp_y;

        // Right
        temp_y = filtCoefTab[0] * outR +
                 filtCoefTab[1] * rx1 +
                 filtCoefTab[2] * rx2 +
                 filtCoefTab[3] * ry1 +
                 filtCoefTab[4] * ry2;
        ry2 = ry1; ry1 = temp_y; rx2 = rx1; rx1 = outR ; outR = temp_y;

        psamples[i] = outL;
        i++;
        psamples[i] = outR;
    };
    return true;
}

void mi::Command(int const i)
{
    switch (i)
    {
    case 0:
        MessageBox(NULL,"PFilter 1.0\n\nThis is an example created from a buzzdev effects tutorial written by CyanPhase","About PFilter",MB_OK|MB_SYSTEMMODAL);
        break;
    default:
        break;
    }
}
char const *mi::DescribeValue(int const param, int const value)
{
    static char txt[16];
    switch(param)
    {
    case 0:
        sprintf(txt,"%.1f", (float)value );
        return txt;
        break;
    case 1:
        sprintf(txt,"%.1f%%", ((float)value / 254.0f * 100.0f) );
        return txt;
        break;
    default:
        return NULL;
    }
}

#pragma optimize ("", on) 

DLL_EXPORTS