mindball/Source/DelayLine.h

#pragma once

#include <algorithm>
#include <cmath>
#include <vector>

namespace mindball
{

// Simple fractional-delay ring buffer with linear interpolation.
class DelayLine
{
public:
    void prepare (float maxDelaySamples)
    {
        maxDelay = std::max (1.0f, maxDelaySamples);
        buffer.assign (static_cast<std::size_t> (maxDelay) + 2, 0.0f);
        writePos = 0;
    }

    void clear()
    {
        std::fill (buffer.begin(), buffer.end(), 0.0f);
        writePos = 0;
    }

    void write (float sample)
    {
        buffer[static_cast<std::size_t> (writePos)] = sample;
        writePos = (writePos + 1) % static_cast<int> (buffer.size());
    }

    float read (float delaySamples) const
    {
        if (buffer.empty())
            return 0.0f;

        const float d = std::max (1.0f, std::min (delaySamples, maxDelay - 1.0f));
        const int size = static_cast<int> (buffer.size());
        const float readPos = static_cast<float> (writePos) - d;
        const float floorPos = std::floor (readPos);

        int i0 = static_cast<int> (floorPos) % size;
        if (i0 < 0)
            i0 += size;

        const int i1 = (i0 + 1) % size;
        const float frac = readPos - floorPos;
        return buffer[static_cast<std::size_t> (i0)]
             + (buffer[static_cast<std::size_t> (i1)] - buffer[static_cast<std::size_t> (i0)]) * frac;
    }

private:
    std::vector<float> buffer;
    float maxDelay = 1.0f;
    int writePos = 0;
};

}