Component.h

/******************************************************************************
DSPatch - The Refreshingly Simple C++ Dataflow Framework
Copyright (c) 2024, Marcus Tomlinson
 
BSD 2-Clause License
 
Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are met:
 
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#pragma once
 
#include "SignalBus.h"
 
#include <algorithm>
#include <atomic>
#include <string>
#include <thread>
#include <vector>
 
namespace DSPatch
{
 
 
class Component
{
public:
    Component( const Component& ) = delete;
    Component& operator=( const Component& ) = delete;
 
    using SPtr = std::shared_ptr<Component>;
 
    enum class ProcessOrder
    {
        InOrder,
        OutOfOrder
    };
 
    Component( ProcessOrder processOrder = ProcessOrder::InOrder );
    virtual ~Component();
 
    bool ConnectInput( const Component::SPtr& fromComponent, int fromOutput, int toInput );
 
    void DisconnectInput( int inputNo );
    void DisconnectInput( const Component::SPtr& fromComponent );
    void DisconnectAllInputs();
 
    int GetInputCount() const;
    int GetOutputCount() const;
 
    std::string GetInputName( int inputNo ) const;
    std::string GetOutputName( int outputNo ) const;
 
    void SetBufferCount( int bufferCount, int startBuffer );
    int GetBufferCount() const;
 
    void Tick( int bufferNo );
    void TickParallel( int bufferNo );
 
    void Scan( std::vector<Component*>& components );
    void ScanParallel( std::vector<std::vector<DSPatch::Component*>>& componentsMap, int& scanPosition );
    void EndScan();
 
protected:
    inline virtual void Process_( SignalBus&, SignalBus& ) = 0;
 
    void SetInputCount_( int inputCount, const std::vector<std::string>& inputNames = {} );
    void SetOutputCount_( int outputCount, const std::vector<std::string>& outputNames = {} );
 
private:
    class AtomicFlag final
    {
    public:
        AtomicFlag( const AtomicFlag& ) = delete;
        AtomicFlag& operator=( const AtomicFlag& ) = delete;
 
        inline AtomicFlag() = default;
 
        inline AtomicFlag( AtomicFlag&& )
        {
        }
 
        inline void WaitAndClear()
        {
            while ( flag.test_and_set( std::memory_order_acquire ) )
            {
                std::this_thread::yield();
            }
        }
 
        inline void Set()
        {
            flag.clear( std::memory_order_release );
        }
 
        inline void Clear()
        {
            flag.test_and_set( std::memory_order_acquire );
        }
 
    private:
        std::atomic_flag flag = { true };  // true here actually means unset / cleared
    };
 
    struct RefCounter final
    {
        int count = 0;
        int total = 0;
        AtomicFlag readyFlag;
    };
 
    struct Wire final
    {
        DSPatch::Component* fromComponent;
        int fromOutput;
        int toInput;
    };
 
    void _WaitForRelease( int bufferNo );
    void _ReleaseNextBuffer( int bufferNo );
 
    void _GetOutput( int bufferNo, int fromOutput, int toInput, DSPatch::SignalBus& toBus );
    void _GetOutputParallel( int bufferNo, int fromOutput, int toInput, DSPatch::SignalBus& toBus );
 
    void _IncRefs( int output );
    void _DecRefs( int output );
 
    const DSPatch::Component::ProcessOrder _processOrder;
 
    int _bufferCount = 0;
 
    std::vector<DSPatch::SignalBus> _inputBuses;
    std::vector<DSPatch::SignalBus> _outputBuses;
 
    std::vector<std::vector<RefCounter>> _refs;  // RefCounter per output, per buffer
 
    std::vector<Wire> _inputWires;
 
    std::vector<AtomicFlag> _releaseFlags;
 
    std::vector<std::string> _inputNames;
    std::vector<std::string> _outputNames;
 
    int _scanPosition = -1;
};
 
inline Component::Component( ProcessOrder processOrder )
    : _processOrder( processOrder )
{
    SetBufferCount( 1, 0 );
}
 
inline Component::~Component() = default;
 
inline bool Component::ConnectInput( const Component::SPtr& fromComponent, int fromOutput, int toInput )
{
    if ( fromOutput >= fromComponent->GetOutputCount() || toInput >= GetInputCount() )
    {
        return false;
    }
 
    // first make sure there are no wires already connected to this input
    auto findFn = [&toInput]( const auto& wire ) { return wire.toInput == toInput; };
 
    if ( auto it = std::find_if( _inputWires.begin(), _inputWires.end(), findFn ); it != _inputWires.end() )
    {
        if ( it->fromComponent == fromComponent.get() && it->fromOutput == fromOutput )
        {
            // this wire already exists
            return true;
        }
 
        // update source output's reference count
        it->fromComponent->_DecRefs( it->fromOutput );
 
        // clear input
        for ( auto& inputBus : _inputBuses )
        {
            inputBus.ClearValue( toInput );
        }
 
        // replace wire
        it->fromComponent = fromComponent.get();
        it->fromOutput = fromOutput;
    }
    else
    {
        // add new wire
        _inputWires.emplace_back( Wire{ fromComponent.get(), fromOutput, toInput } );
    }
 
    // update source output's reference count
    fromComponent->_IncRefs( fromOutput );
 
    return true;
}
 
inline void Component::DisconnectInput( int inputNo )
{
    // remove wires connected to inputNo from _inputWires
    auto findFn = [&inputNo]( const auto& wire ) { return wire.toInput == inputNo; };
 
    if ( auto it = std::find_if( _inputWires.begin(), _inputWires.end(), findFn ); it != _inputWires.end() )
    {
        // update source output's reference count
        it->fromComponent->_DecRefs( it->fromOutput );
 
        // clear input
        for ( auto& inputBus : _inputBuses )
        {
            inputBus.ClearValue( inputNo );
        }
 
        // remove wire
        _inputWires.erase( it );
    }
}
 
inline void Component::DisconnectInput( const Component::SPtr& fromComponent )
{
    // remove fromComponent from _inputWires
    auto findFn = [&fromComponent]( const auto& wire ) { return wire.fromComponent == fromComponent.get(); };
 
    for ( auto it = std::find_if( _inputWires.begin(), _inputWires.end(), findFn ); it != _inputWires.end();
          it = std::find_if( it, _inputWires.end(), findFn ) )
    {
        // update source output's reference count
        fromComponent->_DecRefs( it->fromOutput );
 
        // clear input
        for ( auto& inputBus : _inputBuses )
        {
            inputBus.ClearValue( it->toInput );
        }
 
        // remove wire
        it = _inputWires.erase( it );
    }
}
 
inline void Component::DisconnectAllInputs()
{
    // update all source output reference counts
    for ( const auto& wire : _inputWires )
    {
        wire.fromComponent->_DecRefs( wire.fromOutput );
    }
 
    // clear all inputs
    for ( auto& inputBus : _inputBuses )
    {
        inputBus.ClearAllValues();
    }
 
    // remove all wires
    _inputWires.clear();
}
 
inline int Component::GetInputCount() const
{
    return _inputBuses[0].GetSignalCount();
}
 
inline int Component::GetOutputCount() const
{
    return _outputBuses[0].GetSignalCount();
}
 
// cppcheck-suppress unusedFunction
inline std::string Component::GetInputName( int inputNo ) const
{
    if ( inputNo < (int)_inputNames.size() )
    {
        return _inputNames[inputNo];
    }
    return "";
}
 
// cppcheck-suppress unusedFunction
inline std::string Component::GetOutputName( int outputNo ) const
{
    if ( outputNo < (int)_outputNames.size() )
    {
        return _outputNames[outputNo];
    }
    return "";
}
 
inline void Component::SetBufferCount( int bufferCount, int startBuffer )
{
    // _bufferCount is the current thread count / bufferCount is new thread count
 
    if ( bufferCount <= 0 )
    {
        bufferCount = 1;  // there needs to be at least 1 buffer
    }
 
    if ( startBuffer >= bufferCount )
    {
        startBuffer = 0;
    }
 
    // resize vectors
    _inputBuses.resize( bufferCount );
    _outputBuses.resize( bufferCount );
 
    _releaseFlags.resize( bufferCount );
 
    _refs.resize( bufferCount );
 
    const auto inputCount = GetInputCount();
    const auto outputCount = GetOutputCount();
    const auto refCount = _refs[0].size();
 
    // init vector values
    for ( int i = 0; i < bufferCount; ++i )
    {
        _inputBuses[i].SetSignalCount( inputCount );
        _outputBuses[i].SetSignalCount( outputCount );
 
        if ( i == startBuffer )
        {
            _releaseFlags[i].Set();
        }
        else
        {
            _releaseFlags[i].Clear();
        }
 
        _refs[i].resize( refCount );
        for ( size_t j = 0; j < refCount; ++j )
        {
            // sync output reference counts
            _refs[i][j].total = _refs[0][j].total;
        }
    }
 
    _bufferCount = bufferCount;
}
 
inline int Component::GetBufferCount() const
{
    return _bufferCount;
}
 
inline void Component::Tick( int bufferNo )
{
    auto& inputBus = _inputBuses[bufferNo];
 
    for ( const auto& wire : _inputWires )
    {
        // get new inputs from incoming components
        wire.fromComponent->_GetOutput( bufferNo, wire.fromOutput, wire.toInput, inputBus );
    }
 
    if ( _bufferCount != 1 && _processOrder == ProcessOrder::InOrder )
    {
        // wait for our turn to process
        _WaitForRelease( bufferNo );
 
        // call Process_() with newly aquired inputs
        Process_( inputBus, _outputBuses[bufferNo] );
 
        // signal that we're done processing
        _ReleaseNextBuffer( bufferNo );
    }
    else
    {
        // call Process_() with newly aquired inputs
        Process_( inputBus, _outputBuses[bufferNo] );
    }
}
 
inline void Component::TickParallel( int bufferNo )
{
    auto& inputBus = _inputBuses[bufferNo];
 
    for ( const auto& wire : _inputWires )
    {
        // get new inputs from incoming components
        wire.fromComponent->_GetOutputParallel( bufferNo, wire.fromOutput, wire.toInput, inputBus );
    }
 
    if ( _bufferCount != 1 && _processOrder == ProcessOrder::InOrder )
    {
        // wait for our turn to process
        _WaitForRelease( bufferNo );
 
        // call Process_() with newly aquired inputs
        Process_( inputBus, _outputBuses[bufferNo] );
 
        // signal that we're done processing
        _ReleaseNextBuffer( bufferNo );
    }
    else
    {
        // call Process_() with newly aquired inputs
        Process_( inputBus, _outputBuses[bufferNo] );
    }
 
    // signal that our outputs are ready
    for ( auto& ref : _refs[bufferNo] )
    {
        // readyFlags are cleared in _GetOutputParallel() which ofc is only called on outputs with refs
        if ( ref.total != 0 )
        {
            ref.readyFlag.Set();
        }
    }
}
 
inline void Component::Scan( std::vector<Component*>& components )
{
    // continue only if this component has not already been scanned
    if ( _scanPosition != -1 )
    {
        return;
    }
 
    // initialize _scanPosition
    _scanPosition = 0;
 
    for ( const auto& wire : _inputWires )
    {
        // scan incoming components
        wire.fromComponent->Scan( components );
    }
 
    components.emplace_back( this );
}
 
inline void Component::ScanParallel( std::vector<std::vector<DSPatch::Component*>>& componentsMap, int& scanPosition )
{
    // continue only if this component has not already been scanned
    if ( _scanPosition != -1 )
    {
        scanPosition = _scanPosition;
        return;
    }
 
    // initialize scanPositions
    _scanPosition = 0;
    scanPosition = 0;
 
    for ( const auto& wire : _inputWires )
    {
        // scan incoming components
        wire.fromComponent->ScanParallel( componentsMap, scanPosition );
 
        // ensure we're using the furthest scanPosition detected
        _scanPosition = std::max( _scanPosition, ++scanPosition );
    }
 
    // insert component at _scanPosition
    while ( (int)componentsMap.size() <= _scanPosition )
    {
        componentsMap.emplace_back( std::vector<DSPatch::Component*>{} );
        componentsMap.back().reserve( componentsMap.capacity() );
    }
    componentsMap[_scanPosition].emplace_back( this );
}
 
inline void Component::EndScan()
{
    // reset _scanPosition
    _scanPosition = -1;
}
 
inline void Component::SetInputCount_( int inputCount, const std::vector<std::string>& inputNames )
{
    _inputNames = inputNames;
 
    for ( auto& inputBus : _inputBuses )
    {
        inputBus.SetSignalCount( inputCount );
    }
 
    _inputWires.reserve( inputCount );
}
 
inline void Component::SetOutputCount_( int outputCount, const std::vector<std::string>& outputNames )
{
    _outputNames = outputNames;
 
    for ( auto& outputBus : _outputBuses )
    {
        outputBus.SetSignalCount( outputCount );
    }
 
    // add reference counters for our new outputs
    for ( auto& ref : _refs )
    {
        ref.resize( outputCount );
    }
}
 
inline void Component::_WaitForRelease( int bufferNo )
{
    _releaseFlags[bufferNo].WaitAndClear();
}
 
inline void Component::_ReleaseNextBuffer( int bufferNo )
{
    if ( ++bufferNo == _bufferCount )  // release the next available buffer
    {
        _releaseFlags[0].Set();
    }
    else
    {
        _releaseFlags[bufferNo].Set();
    }
}
 
inline void Component::_GetOutput( int bufferNo, int fromOutput, int toInput, DSPatch::SignalBus& toBus )
{
    auto& signal = *_outputBuses[bufferNo].GetSignal( fromOutput );
 
    if ( !signal.has_value() )
    {
        toBus.ClearValue( toInput );
        return;
    }
 
    auto& ref = _refs[bufferNo][fromOutput];
 
    if ( ref.total == 1 )
    {
        // there's only one reference, move the signal
        toBus.MoveSignal( toInput, signal );
    }
    else if ( ++ref.count != ref.total )
    {
        // this is not the final reference, copy the signal
        toBus.SetSignal( toInput, signal );
    }
    else
    {
        // this is the final reference, reset the counter, move the signal
        ref.count = 0;
        toBus.MoveSignal( toInput, signal );
    }
}
 
inline void Component::_GetOutputParallel( int bufferNo, int fromOutput, int toInput, DSPatch::SignalBus& toBus )
{
    auto& signal = *_outputBuses[bufferNo].GetSignal( fromOutput );
    auto& ref = _refs[bufferNo][fromOutput];
 
    // wait for this output to be ready
    ref.readyFlag.WaitAndClear();
 
    if ( !signal.has_value() )
    {
        toBus.ClearValue( toInput );
 
        if ( ref.total != 1 )
        {
            if ( ++ref.count != ref.total )
            {
                // this is not the final reference, wake next WaitAndClear()
                ref.readyFlag.Set();
            }
            else
            {
                // this is the final reference, reset the counter
                ref.count = 0;
            }
        }
    }
    else if ( ref.total == 1 )
    {
        // there's only one reference, move the signal
        toBus.MoveSignal( toInput, signal );
    }
    else if ( ++ref.count != ref.total )
    {
        // this is not the final reference, copy the signal, wake next WaitAndClear()
        toBus.SetSignal( toInput, signal );
        ref.readyFlag.Set();
    }
    else
    {
        // this is the final reference, reset the counter, move the signal
        ref.count = 0;
        toBus.MoveSignal( toInput, signal );
    }
}
 
inline void Component::_IncRefs( int output )
{
    for ( auto& ref : _refs )
    {
        ++ref[output].total;
    }
}
 
inline void Component::_DecRefs( int output )
{
    for ( auto& ref : _refs )
    {
        --ref[output].total;
    }
}
 
}  // namespace DSPatch