SignalBus.h

/******************************************************************************
DSPatch - The Refreshingly Simple C++ Dataflow Framework
Copyright (c) 2023, Marcus Tomlinson
 
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#pragma once
 
#include <dspatch/Common.h>
 
#include <fast_any/any.h>
 
#include <vector>
 
namespace DSPatch
{
 
 
class DLLEXPORT SignalBus final
{
public:
    NONCOPYABLE( SignalBus );
 
    inline SignalBus();
    inline SignalBus( SignalBus&& );
 
    inline void SetSignalCount( int signalCount );
    inline int GetSignalCount() const;
 
    inline fast_any::any* GetSignal( int signalIndex );
 
    inline bool HasValue( int signalIndex ) const;
 
    template <typename ValueType>
    inline ValueType* GetValue( int signalIndex ) const;
 
    template <typename ValueType>
    inline void SetValue( int signalIndex, const ValueType& newValue );
 
    template <typename ValueType>
    inline void MoveValue( int signalIndex, ValueType&& newValue );
 
    inline void SetSignal( int toSignalIndex, const fast_any::any& fromSignal );
    inline void MoveSignal( int toSignalIndex, fast_any::any& fromSignal );
 
    inline void ClearAllValues();
 
    inline const fast_any::type_info& GetType( int signalIndex ) const;
 
private:
    std::vector<fast_any::any> _signals;
};
 
inline SignalBus::SignalBus() = default;
 
// cppcheck-suppress missingMemberCopy
inline SignalBus::SignalBus( SignalBus&& rhs )
    : _signals( std::move( rhs._signals ) )
{
}
 
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, design, and performance reasons. Usability, because a pointer allows
    // the user to manipulate the contained value externally. Design, because DSPatch doesn't use
    // exceptions - a nullptr return here is the equivalent of "signal does not exist".
    // 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.
 
    if ( (size_t)signalIndex < _signals.size() )
    {
        return &_signals[signalIndex];
    }
    else
    {
        return nullptr;
    }
}
 
inline bool SignalBus::HasValue( int signalIndex ) const
{
    if ( (size_t)signalIndex < _signals.size() )
    {
        return _signals[signalIndex].has_value();
    }
    else
    {
        return false;
    }
}
 
template <typename ValueType>
inline ValueType* SignalBus::GetValue( int signalIndex ) const
{
    // You might be thinking: Why the raw pointer return here?
 
    // See: GetSignal().
 
    if ( (size_t)signalIndex < _signals.size() )
    {
        return _signals[signalIndex].as<ValueType>();
    }
    else
    {
        return nullptr;
    }
}
 
template <typename ValueType>
inline void SignalBus::SetValue( int signalIndex, const ValueType& newValue )
{
    if ( (size_t)signalIndex < _signals.size() )
    {
        _signals[signalIndex].emplace<ValueType>( newValue );
    }
}
 
template <typename ValueType>
inline void SignalBus::MoveValue( int signalIndex, ValueType&& newValue )
{
    if ( (size_t)signalIndex < _signals.size() )
    {
        _signals[signalIndex].emplace<ValueType>( std::move( newValue ) );
    }
}
 
inline void SignalBus::SetSignal( int toSignalIndex, const fast_any::any& fromSignal )
{
    if ( (size_t)toSignalIndex < _signals.size() )
    {
        _signals[toSignalIndex] = 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.
 
    if ( (size_t)toSignalIndex < _signals.size() )
    {
        _signals[toSignalIndex].swap( fromSignal );
    }
}
 
inline void SignalBus::ClearAllValues()
{
    for ( auto& signal : _signals )
    {
        signal.reset();
    }
}
 
inline const fast_any::type_info& SignalBus::GetType( int signalIndex ) const
{
    if ( (size_t)signalIndex < _signals.size() )
    {
        return _signals[signalIndex].type();
    }
    else
    {
        return fast_any::type_id<void>;
    }
}
 
}  // namespace DSPatch