monostep/Source/dsp/StepSequencer.h

#pragma once

#include <array>
#include <cmath>

namespace monostep
{

static constexpr int numSteps   = 16;
static constexpr int minSemitone = -12;
static constexpr int maxSemitone = 12;
static constexpr int numRows    = maxSemitone - minSemitone + 1;

struct Step
{
    bool gate    = false;
    int  semitone = 0;    // -12 .. +12
    float cents  = 0.0f;  // -50 .. +50
    bool slide   = false;
    bool accent  = false;
};

class StepSequencer
{
public:
    Step& step (int i) { return steps[i]; }
    const Step& step (int i) const { return steps[i]; }

    void clear()
    {
        for (auto& s : steps)
            s = Step{};
    }

    void shift (int dir)
    {
        if (dir == 0)
            return;

        std::array<Step, numSteps> rotated = steps;

        for (int i = 0; i < numSteps; ++i)
        {
            const int from = (i - dir + numSteps) % numSteps;
            steps[i] = rotated[from];
        }
    }

    int stepsPerBeatFromRate (int rateIndex) const
    {
        // 0: 1/4, 1: 1/8, 2: 1/8T, 3: 1/16, 4: 1/32
        switch (rateIndex)
        {
            case 0: return 1;
            case 1: return 2;
            case 2: return 3;
            case 4: return 8;
            default: return 4;
        }
    }

    float stepLenPpq (int rateIndex) const
    {
        return 1.0f / (float) stepsPerBeatFromRate (rateIndex);
    }

private:
    std::array<Step, numSteps> steps;
};

} // namespace monostep