chromaflock/Source/DSP/Delay.h

#pragma once
#include <vector>
#include <algorithm>
#include <cmath>

class Delay {
public:
    void prepare(double sr) {
        sampleRate = sr;
        int maxSamples = static_cast<int>(sr * 2.0);
        bufferL.resize(maxSamples, 0.0f);
        bufferR.resize(maxSamples, 0.0f);
        writePos = 0;
    }

    void setParameters(float timeMs, float fb, float mx, bool pingpong = false) {
        timeSamplesF = timeMs * 0.001f * static_cast<float>(sampleRate);
        float bufMax = static_cast<float>(bufferL.size()) - 1.0f;
        timeSamplesF = std::clamp(timeSamplesF, 1.0f, bufMax);
        feedback = std::clamp(fb, 0.0f, 0.95f);
        mix = std::clamp(mx, 0.0f, 1.0f);
        pingPong = pingpong;
    }

    void process(float& left, float& right) {
        int bufSize = static_cast<int>(bufferL.size());

        float readPosF = static_cast<float>(writePos) - timeSamplesF;
        while (readPosF < 0.0f) readPosF += static_cast<float>(bufSize);

        int i0 = static_cast<int>(readPosF) % bufSize;
        int i1 = (i0 + 1) % bufSize;
        float frac = readPosF - std::floor(readPosF);

        float outL = bufferL[i0] * (1.0f - frac) + bufferL[i1] * frac;
        float outR = bufferR[i0] * (1.0f - frac) + bufferR[i1] * frac;

        if (pingPong) {
            // Classic ping-pong: the (summed) input enters one line and each
            // echo is bounced to the opposite channel on the next repeat, so the
            // taps alternate L/R. Only the cross-coupled echo is fed into the
            // opposite line (never the dry input) so the bounce is audible even
            // for a mono source where L == R.
            float in = 0.5f * (left + right);
            bufferL[writePos] = in + outR * feedback;
            bufferR[writePos] =      outL * feedback;
        } else {
            bufferL[writePos] = left + outL * feedback;
            bufferR[writePos] = right + outR * feedback;
        }

        writePos = (writePos + 1) % bufSize;

        left = left * (1.0f - mix) + outL * mix;
        right = right * (1.0f - mix) + outR * mix;
    }

private:
    std::vector<float> bufferL, bufferR;
    int writePos = 0;
    double sampleRate = 44100;
    float timeSamplesF = 8820.0f;
    float feedback = 0.3f;
    float mix = 0.25f;
    bool pingPong = false;
};