nway_crossfade.hpp

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#pragma once
 
#include "crossfade.hpp"
 
#include <algorithm>
#include <cmath>
#include <cstddef>
#include <limits>
#include <span>
#include <type_traits>
 
namespace pulp::signal {

template <typename SampleType>
inline bool nway_constant_power_gains(SampleType position, std::span<SampleType> gains) noexcept {
    static_assert(std::is_floating_point_v<SampleType>);
    static_assert(std::numeric_limits<SampleType>::max_exponent >
                  std::numeric_limits<std::size_t>::digits);
    if (gains.empty())
        return false;
    std::fill(gains.begin(), gains.end(), SampleType{0});
    if (!std::isfinite(position))
        position = SampleType{0};
    if (position <= SampleType{0}) {
        gains.front() = SampleType{1};
        return true;
    }
    const auto size_exclusive = std::ldexp(SampleType{1}, std::numeric_limits<std::size_t>::digits);
    if (position >= size_exclusive) {
        gains.back() = SampleType{1};
        return true;
    }
    const auto lower = static_cast<std::size_t>(position);
    if (lower >= gains.size() - 1) {
        gains.back() = SampleType{1};
        return true;
    }
    const auto fraction = position - static_cast<SampleType>(lower);
    crossfade_gains(fraction, CrossfadeGainLaw::EqualPower, gains[lower], gains[lower + 1]);
    return true;
}
 
} // namespace pulp::signal