Ichthyostega
806db414dd
* Lumiera source code always was copyrighted by individual contributors * there is no entity "Lumiera.org" which holds any copyrights * Lumiera source code is provided under the GPL Version 2+ == Explanations == Lumiera as a whole is distributed under Copyleft, GNU General Public License Version 2 or above. For this to become legally effective, the ''File COPYING in the root directory is sufficient.'' The licensing header in each file is not strictly necessary, yet considered good practice; attaching a licence notice increases the likeliness that this information is retained in case someone extracts individual code files. However, it is not by the presence of some text, that legally binding licensing terms become effective; rather the fact matters that a given piece of code was provably copyrighted and published under a license. Even reformatting the code, renaming some variables or deleting parts of the code will not alter this legal situation, but rather creates a derivative work, which is likewise covered by the GPL! The most relevant information in the file header is the notice regarding the time of the first individual copyright claim. By virtue of this initial copyright, the first author is entitled to choose the terms of licensing. All further modifications are permitted and covered by the License. The specific wording or format of the copyright header is not legally relevant, as long as the intention to publish under the GPL remains clear. The extended wording was based on a recommendation by the FSF. It can be shortened, because the full terms of the license are provided alongside the distribution, in the file COPYING.
121 lines
3.6 KiB
C++
121 lines
3.6 KiB
C++
/*
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QueryResolver - interface for discovering contents of a scope
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Copyright (C)
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2009, Hermann Vosseler <Ichthyostega@web.de>
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**Lumiera** is free software; you can redistribute it and/or modify it
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under the terms of the GNU General Public License as published by the
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Free Software Foundation; either version 2 of the License, or (at your
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option) any later version. See the file COPYING for further details.
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* *****************************************************************/
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/** @file query-resolver.cpp
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** implementation of a framework to query and discover elements
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** based on logical rules. This framework builds on the notion of
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** possibly having several QueryResolver facilities to handle various
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** kinds of queries in an uniform way. To reflect that design, the
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** implementation is built round a DispatcherTable to forward requests
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** to concrete entities implementing the QueryResolver interface. The
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** actual query resolution mechanism is thus not part of the framework.
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**
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*/
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#include "lib/multifact.hpp"
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#include "common/query/query-resolver.hpp"
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namespace lumiera {
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/* generate vtables here... */
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Goal::~Goal() { }
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Resolution::~Resolution() { }
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QueryResolver::~QueryResolver() { }
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typedef Goal::QueryID const& QID;
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/* == dispatch to resolve typed queries == */
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using lib::factory::BuildRefcountPtr;
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using lib::factory::MultiFact;
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/** factory used as dispatcher table
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* for resolving typed queries */
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typedef MultiFact< Resolution*(Goal const&) // raw signature of fabrication
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, Goal::QueryID // select resolution function by kind-of-Query
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, BuildRefcountPtr // wrapper: manage result set by smart-ptr
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> DispatcherTable; //
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/** PImpl of the generic QueryResolver */
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class QueryDispatcher
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: public DispatcherTable
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{
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public:
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PReso
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handle (Goal const& query)
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{
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QID qID = query.getQID();
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ENSURE (contains (qID));
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return this->invokeFactory (qID, query);
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} // qID picks the resolution function
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};
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QueryResolver::QueryResolver ()
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: dispatcher_(new QueryDispatcher)
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{ }
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/** @par implementation
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* For actually building a result set, the QueryResolver base implementation
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* uses an embedded dispatcher table. The concrete query resolving facilities,
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* when implementing the QueryResolver interface, are expected to register
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* individual resolution functions into this QueryDispatcher table.
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* Whenever issuing a Goal, a suitable resolution function is picked
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* based on the Goal::QueryID, which contains an embedded type code.
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* Thus, the individual resolution function can (re)establish a
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* typed context and downcast the Goal appropriately
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*/
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PReso
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QueryResolver::issue (Goal const& query) const
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{
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REQUIRE (!dispatcher_->empty(), "attempt to issue a query without having installed any resolver (yet)");
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if (!canHandle (query))
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throw lumiera::error::Invalid ("unable to resolve this kind of query"); //////////////////////////////////TICKET #197
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return dispatcher_->handle(query);
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}
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void
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QueryResolver::installResolutionCase (QID qID, ResolutionMechanism resolutionFun)
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{
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ENSURE (!dispatcher_->contains (qID),
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"duplicate registration of query resolution function");
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dispatcher_->defineProduction (qID, resolutionFun);
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}
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} // namespace lumiera
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