SignalBus.h

/******************************************************************************
DSPatch - The Refreshingly Simple C++ Dataflow Framework
Copyright (c) 2024, Marcus Tomlinson
 
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#pragma once
 
#include "../fast_any/any.h"
 
#include <vector>
 
namespace DSPatch
{
 
 
class SignalBus final
{
public:
    SignalBus( const SignalBus& ) = delete;
    SignalBus& operator=( const SignalBus& ) = delete;
 
    SignalBus();
    SignalBus( SignalBus&& );
    ~SignalBus();
 
    void SetSignalCount( int signalCount );
    int GetSignalCount() const;
 
    fast_any::any* GetSignal( int signalIndex );
 
    bool HasValue( int signalIndex ) const;
 
    template <typename ValueType>
    ValueType* GetValue( int signalIndex ) const;
 
    template <typename ValueType>
    void SetValue( int signalIndex, const ValueType& newValue );
 
    template <typename ValueType>
    void MoveValue( int signalIndex, ValueType&& newValue );
 
    void SetSignal( int toSignalIndex, const fast_any::any& fromSignal );
    void MoveSignal( int toSignalIndex, fast_any::any& fromSignal );
 
    void ClearValue( int signalIndex );
    void ClearAllValues();
 
    fast_any::type_info GetType( int signalIndex ) const;
 
private:
    std::vector<fast_any::any> _signals;
};
 
inline SignalBus::SignalBus() = default;
 
inline SignalBus::SignalBus( SignalBus&& rhs )
    : _signals( std::move( rhs._signals ) )
{
}
 
inline SignalBus::~SignalBus() = default;
 
inline void SignalBus::SetSignalCount( int signalCount )
{
    _signals.resize( signalCount );
}
 
inline int SignalBus::GetSignalCount() const
{
    return (int)_signals.size();
}
 
inline fast_any::any* SignalBus::GetSignal( int signalIndex )
{
    // You might be thinking: Why the raw pointer return here?
 
    // This is for usability and performance reasons. Usability, because a pointer allows the user
    // to manipulate the contained value externally. Performance, because returning a smart pointer
    // means having to store the value as a smart pointer too - this adds yet another level of
    // indirection to the value, as well as some reference counting overhead. These Get() and Set()
    // methods are VERY frequently called, so doing as little as possible with the data here is best.
 
    return &_signals[signalIndex];
}
 
inline bool SignalBus::HasValue( int signalIndex ) const
{
    return _signals[signalIndex].has_value();
}
 
template <typename ValueType>
inline ValueType* SignalBus::GetValue( int signalIndex ) const
{
    // You might be thinking: Why the raw pointer return here?
 
    // See: GetSignal().
 
    return _signals[signalIndex].as<ValueType>();
}
 
template <typename ValueType>
inline void SignalBus::SetValue( int signalIndex, const ValueType& newValue )
{
    _signals[signalIndex].emplace<ValueType>( newValue );
}
 
template <typename ValueType>
inline void SignalBus::MoveValue( int signalIndex, ValueType&& newValue )
{
    _signals[signalIndex].emplace<ValueType>( std::forward<ValueType>( newValue ) );
}
 
inline void SignalBus::SetSignal( int toSignalIndex, const fast_any::any& fromSignal )
{
    _signals[toSignalIndex].emplace( fromSignal );
}
 
inline void SignalBus::MoveSignal( int toSignalIndex, fast_any::any& fromSignal )
{
    // You might be thinking: Why swap and not move here?
 
    // This is a really nifty little optimisation actually. When we move a signal value from an
    // output to an input (or vice-versa within a component) we move its type_info along with it.
    // If you look at any::emplace(), you'll see that type_info is really useful in determining
    // whether we need to delete and copy (re)construct our contained value, or can simply copy
    // assign. To avoid the former as much as possible, a swap is done between source and target
    // signals such that, between these two points, just two value holders need to be constructed,
    // and shared back and forth from then on.
 
    _signals[toSignalIndex].swap( fromSignal );
}
 
inline void SignalBus::ClearValue( int signalIndex )
{
    _signals[signalIndex].reset();
}
 
inline void SignalBus::ClearAllValues()
{
    for ( auto& signal : _signals )
    {
        signal.reset();
    }
}
 
inline fast_any::type_info SignalBus::GetType( int signalIndex ) const
{
    return _signals[signalIndex].type();
}
 
}  // namespace DSPatch