interpolate.h

#pragma once
#include "definitions_cxx.hpp"
#include "deluge/dsp/stereo_sample.h"
#include <array>
#include <cstdint>
 
extern const int16_t windowedSincKernel[][17][16];
 
namespace deluge::dsp {
struct [[gnu::hot]] Interpolator {
 
    Interpolator() = default;
    StereoSample interpolate(size_t channels, int32_t whichKernel, uint32_t oscPos);
    StereoSample interpolateLinear(size_t channels, uint32_t oscPos);
 
    [[gnu::always_inline]] constexpr void pushL(int16_t value) {
#pragma unroll
        for (int32_t i = kInterpolationMaxNumSamples - 1; i >= 1; i--) {
            buffer_l[i] = buffer_l[i - 1];
        }
        buffer_l[0] = value;
    }
 
    [[gnu::always_inline]] constexpr void pushR(int16_t value) {
#pragma unroll
        for (int32_t i = kInterpolationMaxNumSamples - 1; i >= 1; i--) {
            buffer_r[i] = buffer_r[i - 1];
        }
        buffer_r[0] = value;
    }
 
    [[gnu::always_inline]] constexpr void jumpForward(size_t num_samples) {
#pragma unroll
        for (int32_t i = kInterpolationMaxNumSamples - 1; i >= num_samples; i--) {
            buffer_l[i] = buffer_l[i - num_samples];
            buffer_r[i] = buffer_r[i - num_samples];
        }
    }
 
    // These are the state buffers (quadword alignment for NEON). Value-initialised: interpolate() reads the full
    // kInterpolationMaxNumSamples-tap window via SIMD, so any tap not yet pushed must be a defined 0 rather than
    // whatever the allocation left behind (the live-input pitch-shifter feeds these incrementally on warm-up).
    alignas(sizeof(int32_t) * 4) std::array<int16_t, kInterpolationMaxNumSamples> buffer_l{};
    alignas(sizeof(int32_t) * 4) std::array<int16_t, kInterpolationMaxNumSamples> buffer_r{};
};
} // namespace deluge::dsp