AudioBufferView.h

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/*
 * AudioBufferView.h - Non-owning views for interleaved and
 *                     non-interleaved (planar) buffers
 *
 * Copyright (c) 2025 Dalton Messmer <messmer.dalton/at/gmail.com>
 *
 * This file is part of LMMS - https://lmms.io
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program (see COPYING); if not, write to the
 * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA 02110-1301 USA.
 *
 */
 
#ifndef LMMS_AUDIO_BUFFER_VIEW_H
#define LMMS_AUDIO_BUFFER_VIEW_H
 
#include <cassert>
#include <concepts>
#include <ranges>
#include <span>
#include <type_traits>
 
#include "LmmsTypes.h"
#include "SampleFrame.h"
 
namespace lmms
{

inline constexpr auto DynamicChannelCount = static_cast<ch_cnt_t>(-1);
 
 
namespace detail {
 
// For buffer views with static channel count
template<typename T, ch_cnt_t channelCount>
class BufferViewData
{
public:
        constexpr BufferViewData() = default;
        constexpr BufferViewData(const BufferViewData&) = default;
 
        constexpr BufferViewData(T* data, [[maybe_unused]] ch_cnt_t channels, f_cnt_t frames) noexcept
                : m_data{data}
                , m_frames{frames}
        {
                assert(channels == channelCount);
        }
 
        constexpr BufferViewData(T* data, f_cnt_t frames) noexcept
                : m_data{data}
                , m_frames{frames}
        {
        }
 
        constexpr auto data() const noexcept -> T* { return m_data; }
        static constexpr auto channels() noexcept -> ch_cnt_t { return channelCount; }
        constexpr auto frames() const noexcept -> f_cnt_t { return m_frames; }
 
protected:
        T* m_data = nullptr;
        f_cnt_t m_frames = 0;
};
 
// For buffer views with dynamic channel count
template<typename T>
class BufferViewData<T, DynamicChannelCount>
{
public:
        constexpr BufferViewData() = default;
        constexpr BufferViewData(const BufferViewData&) = default;
 
        constexpr BufferViewData(T* data, ch_cnt_t channels, f_cnt_t frames) noexcept
                : m_data{data}
                , m_channels{channels}
                , m_frames{frames}
        {
                assert(channels != DynamicChannelCount);
        }
 
        constexpr auto data() const noexcept -> T* { return m_data; }
        constexpr auto channels() const noexcept -> ch_cnt_t { return m_channels; }
        constexpr auto frames() const noexcept -> f_cnt_t { return m_frames; }
 
protected:
        T* m_data = nullptr;
        ch_cnt_t m_channels = 0;
        f_cnt_t m_frames = 0;
};
 
// For interleaved frame iterators with static channel count
template<typename T, ch_cnt_t channelCount>
class InterleavedFrameIteratorData
{
public:
        constexpr InterleavedFrameIteratorData() = default;
        constexpr InterleavedFrameIteratorData(const InterleavedFrameIteratorData&) = default;
 
        constexpr explicit InterleavedFrameIteratorData(T* data) noexcept
                : m_data{data}
        {
        }
 
        static constexpr auto channels() noexcept -> ch_cnt_t { return channelCount; }
 
protected:
        T* m_data = nullptr;
};
 
// For interleaved frame iterators with dynamic channel count
template<typename T>
class InterleavedFrameIteratorData<T, DynamicChannelCount>
{
public:
        constexpr InterleavedFrameIteratorData() = default;
        constexpr InterleavedFrameIteratorData(const InterleavedFrameIteratorData&) = default;
 
        constexpr InterleavedFrameIteratorData(T* data, ch_cnt_t channels) noexcept
                : m_data{data}
                , m_channels{channels}
        {
        }
 
        constexpr auto channels() const noexcept -> ch_cnt_t { return m_channels; }
 
protected:
        T* m_data = nullptr;
        ch_cnt_t m_channels = 0;
};
 
// Allows for iterating over the frames of `InterleavedBufferView`
template<typename T, ch_cnt_t channelCount = DynamicChannelCount>
class InterleavedFrameIterator : public InterleavedFrameIteratorData<T, channelCount>
{
        using Base = InterleavedFrameIteratorData<T, channelCount>;
 
public:
        using iterator_concept = std::random_access_iterator_tag;
        using value_type = T*;
        using difference_type = std::ptrdiff_t;
 
        using Base::Base;
 
        constexpr auto operator*() const noexcept -> value_type { return this->m_data; }
 
        constexpr auto operator[](difference_type frames) const noexcept -> value_type
        {
                return this->m_data[frames * Base::channels()];
        }
 
        constexpr auto operator++() noexcept -> InterleavedFrameIterator&
        {
                this->m_data += Base::channels();
                return *this;
        }
 
        constexpr auto operator++(int) noexcept -> InterleavedFrameIterator
        {
                auto temp = *this;
                ++(*this);
                return temp;
        }
 
        constexpr auto operator--() noexcept -> InterleavedFrameIterator&
        {
                this->m_data -= Base::channels();
                return *this;
        }
 
        constexpr auto operator--(int) noexcept -> InterleavedFrameIterator
        {
                auto temp = *this;
                --(*this);
                return temp;
        }
 
        constexpr auto operator+=(difference_type channels) noexcept -> InterleavedFrameIterator&
        {
                this->m_data += channels * Base::channels();
                return *this;
        }
 
        constexpr auto operator-=(difference_type channels) noexcept -> InterleavedFrameIterator&
        {
                this->m_data -= channels * Base::channels();
                return *this;
        }
 
        friend constexpr auto operator+(InterleavedFrameIterator iter, difference_type frames) noexcept
                -> InterleavedFrameIterator
        {
                if constexpr (channelCount == DynamicChannelCount)
                {
                        return {iter.m_data + frames * Base::channels(), Base::channels()};
                }
                else
                {
                        return InterleavedFrameIterator{iter.m_data + frames * Base::channels()};
                }
        }
 
        friend constexpr auto operator+(difference_type frames, InterleavedFrameIterator iter) noexcept
                -> InterleavedFrameIterator
        {
                return iter + frames;
        }
 
        constexpr auto operator-(difference_type frames) const noexcept -> InterleavedFrameIterator
        {
                if constexpr (channelCount == DynamicChannelCount)
                {
                        return {this->m_data - frames * Base::channels(), Base::channels()};
                }
                else
                {
                        return InterleavedFrameIterator{this->m_data - frames * Base::channels()};
                }
        }
 
        constexpr auto operator-(InterleavedFrameIterator other) const noexcept -> difference_type
        {
                return this->m_data - other.m_data;
        }
 
        constexpr auto operator<=>(InterleavedFrameIterator other) const noexcept
        {
                return this->m_data <=> other.m_data;
        }
 
        constexpr auto operator==(InterleavedFrameIterator other) const noexcept -> bool
        {
                return this->m_data == other.m_data;
        }
 
        constexpr auto operator<=>(T* sentinel) const noexcept
        {
                return this->m_data <=> sentinel;
        }
 
        constexpr auto operator==(T* sentinel) const noexcept -> bool
        {
                return this->m_data == sentinel;
        }
 
        constexpr auto base() const noexcept -> T* { return this->m_data; }
};
 
static_assert(std::random_access_iterator<InterleavedFrameIterator<float, 2>>);
 
template<typename T, typename... AllowedTs>
inline constexpr bool OneOf = (std::is_same_v<T, AllowedTs> || ...);
 
} // namespace detail
 

template<typename T>
concept SampleType = detail::OneOf<std::remove_const_t<T>,
        float,
        double,
        std::int8_t,
        std::uint8_t,
        std::int16_t,
        std::uint16_t,
        std::int32_t,
        std::uint32_t,
        std::int64_t,
        std::uint64_t
>;
 

template<SampleType T, ch_cnt_t channelCount = DynamicChannelCount>
class InterleavedBufferView : public detail::BufferViewData<T, channelCount>
{
        using Base = detail::BufferViewData<T, channelCount>;
 
        using FrameIter = detail::InterleavedFrameIterator<T, channelCount>;
        using ConstFrameIter = detail::InterleavedFrameIterator<const T, channelCount>;
 
public:
        using Base::Base;

        template<typename U = T> requires (std::is_const_v<U> && channelCount != DynamicChannelCount)
        constexpr InterleavedBufferView(InterleavedBufferView<std::remove_const_t<U>, channelCount> other) noexcept
                : Base{other.data(), other.frames()}
        {
        }

        template<typename U = T> requires (std::is_const_v<U> && channelCount == DynamicChannelCount)
        constexpr InterleavedBufferView(InterleavedBufferView<std::remove_const_t<U>, channelCount> other) noexcept
                : Base{other.data(), other.channels(), other.frames()}
        {
        }

        template<ch_cnt_t otherChannels>
                requires (channelCount == DynamicChannelCount && otherChannels != DynamicChannelCount)
        constexpr InterleavedBufferView(InterleavedBufferView<T, otherChannels> other) noexcept
                : Base{other.data(), otherChannels, other.frames()}
        {
        }

        InterleavedBufferView(SampleFrame* data, f_cnt_t frames) noexcept
                requires (std::is_same_v<std::remove_const_t<T>, float> && channelCount == 2)
                : Base{reinterpret_cast<float*>(data), frames}
        {
        }

        InterleavedBufferView(const SampleFrame* data, f_cnt_t frames) noexcept
                requires (std::is_same_v<T, const float> && channelCount == 2)
                : Base{reinterpret_cast<const float*>(data), frames}
        {
        }
 
        constexpr auto empty() const noexcept -> bool
        {
                return !this->m_data || Base::channels() == 0 || this->m_frames == 0;
        }
 
        constexpr auto dataSizeBytes() const noexcept -> std::size_t
        {
                return Base::channels() * this->m_frames * sizeof(T);
        }
 
        constexpr auto dataView() noexcept -> std::span<T>
        {
                return std::span<T>{this->m_data, this->m_frames * Base::channels()};
        }

        constexpr auto sample(ch_cnt_t channel, f_cnt_t frame) const noexcept -> T&
        {
                return framePtr(frame)[channel];
        }

        constexpr auto frame(f_cnt_t index) const noexcept
        {
                if constexpr (channelCount == DynamicChannelCount)
                {
                        return std::span<T>{framePtr(index), Base::channels()};
                }
                else
                {
                        return std::span<T, channelCount>{framePtr(index), Base::channels()};
                }
        }

        constexpr auto framePtr(f_cnt_t index) const noexcept -> T*
        {
                assert(index < this->m_frames);
                return this->m_data + index * Base::channels();
        }

        constexpr auto operator[](f_cnt_t index) const noexcept -> T*
        {
                return framePtr(index);
        }

        constexpr auto subspan(f_cnt_t offset, f_cnt_t frames) const -> InterleavedBufferView<T, channelCount>
        {
                assert(offset <= this->m_frames);
                assert(offset + frames <= this->m_frames);
                if constexpr (channelCount == DynamicChannelCount)
                {
                        return {this->m_data + offset * Base::channels(), Base::channels(), frames};
                }
                else
                {
                        return {this->m_data + offset * Base::channels(), frames};
                }
        }

        constexpr auto framesView() const noexcept -> std::ranges::subrange<ConstFrameIter, const T*>
        {
                const T* end = this->m_data + Base::channels() * this->m_frames;
                if constexpr (channelCount == DynamicChannelCount)
                {
                        return std::ranges::subrange{ConstFrameIter{this->m_data, Base::channels()}, end};
                }
                else
                {
                        return std::ranges::subrange{ConstFrameIter{this->m_data}, end};
                }
        }

        constexpr auto framesView() noexcept -> std::ranges::subrange<FrameIter, T*>
        {
                T* end = this->m_data + Base::channels() * this->m_frames;
                if constexpr (channelCount == DynamicChannelCount)
                {
                        return std::ranges::subrange{FrameIter{this->m_data, Base::channels()}, end};
                }
                else
                {
                        return std::ranges::subrange{FrameIter{this->m_data}, end};
                }
        }
 
        auto sampleFrameAt(f_cnt_t index) noexcept -> SampleFrame&
                requires (std::is_same_v<T, float> && channelCount == 2)
        {
                assert(index < this->m_frames);
                return reinterpret_cast<SampleFrame*>(this->m_data)[index];
        }
 
        auto sampleFrameAt(f_cnt_t index) const noexcept -> const SampleFrame&
                requires (std::is_same_v<T, const float> && channelCount == 2)
        {
                assert(index < this->m_frames);
                return reinterpret_cast<const SampleFrame*>(this->m_data)[index];
        }
 
        auto asSampleFrames() noexcept -> std::span<SampleFrame>
                requires (std::is_same_v<T, float> && channelCount == 2)
        {
                return {reinterpret_cast<SampleFrame*>(this->m_data), this->m_frames};
        }
 
        auto asSampleFrames() const noexcept -> std::span<const SampleFrame>
                requires (std::is_same_v<T, const float> && channelCount == 2)
        {
                return {reinterpret_cast<const SampleFrame*>(this->m_data), this->m_frames};
        }

        static constexpr bool Interleaved = true;
};
 
// Check that the std::span-like space optimization works
static_assert(sizeof(InterleavedBufferView<float>) > sizeof(InterleavedBufferView<float, 2>));
static_assert(sizeof(InterleavedBufferView<float, 2>) == sizeof(void*) + sizeof(f_cnt_t));
 
// Deduction guides
InterleavedBufferView(const SampleFrame*, f_cnt_t) -> InterleavedBufferView<const float, 2>;
InterleavedBufferView(SampleFrame*, f_cnt_t) -> InterleavedBufferView<float, 2>;
 

template<SampleType T, ch_cnt_t channelCount = DynamicChannelCount>
class PlanarBufferView : public detail::BufferViewData<T* const, channelCount>
{
        using Base = detail::BufferViewData<T* const, channelCount>;
 
public:
        using Base::Base;

        template<typename U = T> requires (std::is_const_v<U> && channelCount != DynamicChannelCount)
        constexpr PlanarBufferView(PlanarBufferView<std::remove_const_t<U>, channelCount> other) noexcept
                : Base{other.data(), other.frames()}
        {
        }

        template<typename U = T> requires (std::is_const_v<U> && channelCount == DynamicChannelCount)
        constexpr PlanarBufferView(PlanarBufferView<std::remove_const_t<U>, channelCount> other) noexcept
                : Base{other.data(), other.channels(), other.frames()}
        {
        }

        template<ch_cnt_t otherChannels>
                requires (channelCount == DynamicChannelCount && otherChannels != DynamicChannelCount)
        constexpr PlanarBufferView(PlanarBufferView<T, otherChannels> other) noexcept
                : Base{other.data(), otherChannels, other.frames()}
        {
        }
 
        constexpr auto empty() const noexcept -> bool
        {
                return !this->m_data || Base::channels() == 0 || this->m_frames == 0;
        }

        constexpr auto sample(ch_cnt_t channel, f_cnt_t frame) const noexcept -> T&
        {
                return bufferPtr(channel)[frame];
        }

        constexpr auto buffer(ch_cnt_t channel) const noexcept -> std::span<T>
        {
                return {bufferPtr(channel), this->m_frames};
        }

        template<ch_cnt_t channel> requires (channelCount != DynamicChannelCount)
        constexpr auto buffer() const noexcept -> std::span<T>
        {
                return {bufferPtr<channel>(), this->m_frames};
        }

        constexpr auto bufferPtr(ch_cnt_t channel) const noexcept -> T*
        {
                assert(channel < Base::channels());
                assert(this->m_data != nullptr);
                return this->m_data[channel];
        }

        template<ch_cnt_t channel> requires (channelCount != DynamicChannelCount)
        constexpr auto bufferPtr() const noexcept -> T*
        {
                static_assert(channel < channelCount);
                assert(this->m_data != nullptr);
                return this->m_data[channel];
        }

        constexpr auto operator[](ch_cnt_t channel) const noexcept -> T*
        {
                return bufferPtr(channel);
        }

        static constexpr bool Interleaved = false;
};
 
// Check that the std::span-like space optimization works
static_assert(sizeof(PlanarBufferView<float>) > sizeof(PlanarBufferView<float, 2>));
static_assert(sizeof(PlanarBufferView<float, 2>) == sizeof(void**) + sizeof(f_cnt_t));
 

template<class T, typename U, ch_cnt_t channels = DynamicChannelCount>
concept AudioBufferView = SampleType<U> && (std::convertible_to<T, InterleavedBufferView<U, channels>>
        || std::convertible_to<T, PlanarBufferView<U, channels>>);
 

template<class T, ch_cnt_t inputs, ch_cnt_t outputs>
constexpr void toInterleaved(PlanarBufferView<T, inputs> src,
        InterleavedBufferView<std::remove_const_t<T>, outputs> dst)
{
        assert(src.frames() == dst.frames());
        if constexpr (inputs == DynamicChannelCount || outputs == DynamicChannelCount)
        {
                assert(src.channels() == dst.channels());
        }
        else { static_assert(inputs == outputs); }
 
        for (f_cnt_t frame = 0; frame < dst.frames(); ++frame)
        {
                auto* framePtr = dst.framePtr(frame);
                for (ch_cnt_t channel = 0; channel < dst.channels(); ++channel)
                {
                        framePtr[channel] = src.bufferPtr(channel)[frame];
                }
        }
}

template<class T, ch_cnt_t inputs, ch_cnt_t outputs>
constexpr void toPlanar(InterleavedBufferView<T, inputs> src,
        PlanarBufferView<std::remove_const_t<T>, outputs> dst)
{
        assert(src.frames() == dst.frames());
        if constexpr (inputs == DynamicChannelCount || outputs == DynamicChannelCount)
        {
                assert(src.channels() == dst.channels());
        }
        else { static_assert(inputs == outputs); }
 
        for (ch_cnt_t channel = 0; channel < dst.channels(); ++channel)
        {
                auto* channelPtr = dst.bufferPtr(channel);
                for (f_cnt_t frame = 0; frame < dst.frames(); ++frame)
                {
                        channelPtr[frame] = src.framePtr(frame)[channel];
                }
        }
}
 
} // namespace lmms
 
#endif // LMMS_AUDIO_BUFFER_VIEW_H