annotate vamp-support/PreservingPluginHandleMapper.h @ 263:9a044706ab73

Comments on dubiousness of all this

/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */

/*
    Piper C++

    Centre for Digital Music, Queen Mary, University of London.
    Copyright 2006-2016 Chris Cannam and QMUL.
  
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#ifndef PIPER_PRESERVING_PLUGIN_HANDLE_MAPPER_H
#define PIPER_PRESERVING_PLUGIN_HANDLE_MAPPER_H

#include "PluginHandleMapper.h"
#include "PreservingPluginOutputIdMapper.h"

#include <iostream>

namespace piper_vamp {

//!!! document -- this is a passthrough thing for a single plugin
//!!! handle only, it does not use actually valid Plugin pointers at
//!!! all. Or, better, reimplement in a way that doesn't involve
//!!! such alarmingly invalid reinterpret_casts

class PreservingPluginHandleMapper : public PluginHandleMapper
{
public:
    PreservingPluginHandleMapper() :
        m_handle(0),
        m_plugin(0),
        m_omapper(std::make_shared<PreservingPluginOutputIdMapper>()) { }

    virtual Handle pluginToHandle(Vamp::Plugin *p) const noexcept {
        if (!p) return INVALID_HANDLE;
	if (p == m_plugin) return m_handle;
	else {
	    std::cerr << "PreservingPluginHandleMapper: p = " << p
		      << " differs from saved m_plugin " << m_plugin
		      << " (not returning saved handle " << m_handle << ")"
		      << std::endl;
            return INVALID_HANDLE;
	}
    }

    virtual Vamp::Plugin *handleToPlugin(Handle h) const noexcept {
        if (h == INVALID_HANDLE) return nullptr;
	m_handle = h;
        //!!! see comment at top
	m_plugin = reinterpret_cast<Vamp::Plugin *>(h);
	return m_plugin;
    }

    virtual const std::shared_ptr<PluginOutputIdMapper> pluginToOutputIdMapper
    (Vamp::Plugin *p) const noexcept {
        if (!p) return {};
        return m_omapper;
    }
        
    virtual const std::shared_ptr<PluginOutputIdMapper> handleToOutputIdMapper
    (Handle h) const noexcept {
        if (h == INVALID_HANDLE) return {};
        return m_omapper;
    }
    
private:
    mutable Handle m_handle;
    mutable Vamp::Plugin *m_plugin;
    std::shared_ptr<PreservingPluginOutputIdMapper> m_omapper;
};

}

#endif