JUCE/modules/juce_audio_basics/utilities/juce_AudioWorkgroup.cpp

/*
  ==============================================================================

   This file is part of the JUCE framework.
   Copyright (c) Raw Material Software Limited

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   licensing.

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   Or:

   You may also use this code under the terms of the AGPLv3:
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  ==============================================================================
*/

namespace juce
{

#if JUCE_AUDIOWORKGROUP_TYPES_AVAILABLE

class WorkgroupToken::TokenProvider
{
public:
    explicit TokenProvider (os_workgroup_t wg)
        : workgroup (wg), attached (attach (wg, token)) {}

    ~TokenProvider()
    {
        if (attached)
            detach (workgroup, token);
    }

    TokenProvider (const TokenProvider&) = delete;
    TokenProvider (TokenProvider&& other) noexcept
        : workgroup (std::exchange (other.workgroup, os_workgroup_t{})),
          token (std::exchange (other.token, os_workgroup_join_token_s{})),
          attached (std::exchange (other.attached, false)) {}

    TokenProvider& operator= (const TokenProvider&) = delete;
    TokenProvider& operator= (TokenProvider&& other) noexcept
    {
        TokenProvider { std::move (other) }.swap (*this);
        return *this;
    }

    bool isAttached()             const { return attached; }
    os_workgroup_t getHandle()    const { return workgroup; }

private:
    static void detach (os_workgroup_t wg, os_workgroup_join_token_s token)
    {
        if (@available (macOS 11.0, iOS 14.0, *))
            os_workgroup_leave (wg, &token);
    }

    static bool attach (os_workgroup_t wg, os_workgroup_join_token_s& tokenOut)
    {
        if (@available (macOS 11.0, iOS 14.0, *))
        {
            if (wg != nullptr && os_workgroup_join (wg, &tokenOut) == 0)
                return true;
        }

        return false;
    }

    void swap (TokenProvider& other) noexcept
    {
        std::swap (other.workgroup, workgroup);
        std::swap (other.token, token);
        std::swap (other.attached, attached);
    }

    os_workgroup_t workgroup;
    os_workgroup_join_token_s token;
    bool attached;
};

class AudioWorkgroup::WorkgroupProvider
{
public:
    explicit WorkgroupProvider (os_workgroup_t ptr) : handle { ptr } {}

    void join (WorkgroupToken& token) const
    {
        if (const auto* tokenProvider = token.getTokenProvider())
            if (tokenProvider->isAttached() && tokenProvider->getHandle() == handle.get())
                return;

        // Explicit reset before constructing the new workgroup to ensure that the old workgroup
        // is left before the new one is joined.
        token.reset();

        if (handle.get() != nullptr)
            token = WorkgroupToken { [provider = WorkgroupToken::TokenProvider { handle.get() }] { return &provider; } };
    }

    static os_workgroup_t getWorkgroup (const AudioWorkgroup& wg)
    {
        if (auto* provider = wg.getWorkgroupProvider())
            return provider->handle.get();

        return nullptr;
    }

private:
    struct ScopedWorkgroupRetainer
    {
        ScopedWorkgroupRetainer (os_workgroup_t wg) : handle { wg }
        {
            if (handle != nullptr)
                os_retain (handle);
        }

        ~ScopedWorkgroupRetainer()
        {
            if (handle != nullptr)
                os_release (handle);
        }

        ScopedWorkgroupRetainer (const ScopedWorkgroupRetainer& other)
            : ScopedWorkgroupRetainer { other.handle } {}

        ScopedWorkgroupRetainer& operator= (const ScopedWorkgroupRetainer& other)
        {
            ScopedWorkgroupRetainer { other }.swap (*this);
            return *this;
        }

        ScopedWorkgroupRetainer (ScopedWorkgroupRetainer&& other) noexcept
        {
            swap (other);
        }

        ScopedWorkgroupRetainer& operator= (ScopedWorkgroupRetainer&& other) noexcept
        {
            swap (other);
            return *this;
        }

        void swap (ScopedWorkgroupRetainer& other) noexcept
        {
            std::swap (handle, other.handle);
        }

        os_workgroup_t get() const noexcept { return handle; }

    private:
        os_workgroup_t handle { nullptr };
    };

    ScopedWorkgroupRetainer handle;
};

#else

class WorkgroupToken::TokenProvider {};

class AudioWorkgroup::WorkgroupProvider
{
public:
    explicit WorkgroupProvider() = default;

    void join (WorkgroupToken& t) const { t.reset(); }

    static void* getWorkgroup (const AudioWorkgroup&) { return nullptr; }
};

#endif

AudioWorkgroup::AudioWorkgroup (const AudioWorkgroup& other)
    : erased ([&]() -> Erased
              {
                  if (auto* p = other.getWorkgroupProvider())
                      return [provider = *p] { return &provider; };

                  return nullptr;
              }()) {}

bool AudioWorkgroup::operator== (const AudioWorkgroup& other) const
{
    return WorkgroupProvider::getWorkgroup (*this) == WorkgroupProvider::getWorkgroup (other);
}

void AudioWorkgroup::join (WorkgroupToken& token) const
{
   #if JUCE_AUDIOWORKGROUP_TYPES_AVAILABLE

    if (const auto* p = getWorkgroupProvider())
    {
        p->join (token);
        return;
    }

   #endif

    token.reset();
}

size_t AudioWorkgroup::getMaxParallelThreadCount() const
{
   #if JUCE_AUDIOWORKGROUP_TYPES_AVAILABLE

    if (@available (macOS 11.0, iOS 14.0, *))
    {
        if (auto wg = WorkgroupProvider::getWorkgroup (*this))
            return (size_t) os_workgroup_max_parallel_threads (wg, nullptr);
    }

   #endif

   return 0;
}

AudioWorkgroup::operator bool() const { return WorkgroupProvider::getWorkgroup (*this) != nullptr; }

#if JUCE_AUDIOWORKGROUP_TYPES_AVAILABLE

AudioWorkgroup makeRealAudioWorkgroup (os_workgroup_t handle)
{
    if (handle == nullptr)
        return AudioWorkgroup{};

    return AudioWorkgroup { [provider = AudioWorkgroup::WorkgroupProvider { handle }] { return &provider; } };
}

#endif

} // namespace juce