/**************************************************************************** ** ** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies). ** Contact: Qt Software Information (qt-info@nokia.com) ** ** This file is part of the QtXmlPatterns module of the Qt Toolkit. ** ** $QT_BEGIN_LICENSE:LGPL$ ** No Commercial Usage ** This file contains pre-release code and may not be distributed. ** You may use this file in accordance with the terms and conditions ** contained in the either Technology Preview License Agreement or the ** Beta Release License Agreement. ** ** GNU Lesser General Public License Usage ** Alternatively, this file may be used under the terms of the GNU Lesser ** General Public License version 2.1 as published by the Free Software ** Foundation and appearing in the file LICENSE.LGPL included in the ** packaging of this file. 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This header file may change from version to // version without notice, or even be removed. // // We mean it. #ifndef Patternist_ResourceLoader_H #define Patternist_ResourceLoader_H #include "qitem_p.h" #include "qreportcontext_p.h" #include "qsequencetype_p.h" #include "qsourcelocationreflection_p.h" QT_BEGIN_HEADER QT_BEGIN_NAMESPACE class QUrl; namespace QPatternist { /** * @short Responsible for handling requests for opening files and node collections. * * ResourceLoader is a callback used for opening files, requested * via the functions fn:document() and fn:unparsed-text(); * and node collections, requested via fn:collection(). Patternist uses the * ResourceLoader at compile time, * via StaticContext::resourceLoader(), and at runtime, via DynamicContext::resourceLoader(). * * The ResourceLoader takes care of loading "external resources" in a way specific to the data * model Patternist is using. For example, perhaps the opening of documents should pass * a security policy, or a collection should map to nodes in a virtual filesystem or a database. * * From Patternist's perspective, the ResourceLoader provides two things: * * - At compile time, it calls announceDocument(), announceCollection() and announceUnparsedText() * if it knows the URIs at compile time in order to retrieve the static types of the data the URIs * maps to. This is used for more efficiently compiling the query and to better report errors * at compile time. * - To open document and node collections at runtime. * * From the user's or the data model's perspective, the ResourceLoader most notably provides * a hint to what resources a query will load at runtime, and therefore provides an opportunity * to prepare in advance for that. For example, between the compile and runtime stage, * the ResourceLoader sub-class can be asked to pre-load documents in an asynchronous * and simultaneous way, such that the runtime stage is faster and doesn't * freeze a graphical interface. * * The announce functions are not guaranteed to be called. The loading functions can be called * with an URI that an announce function hasn't been called with. * * The default implementations of ResourceLoader's virtual functions all signals that no * resources can be loaded. This means ResourceLoader must be sub-classed, in order to * be able to load resources. * * @ingroup Patternist_xdm * @author Frans Englich */ class Q_AUTOTEST_EXPORT ResourceLoader : public QSharedData { public: enum Usage { /** * Communicates that the URI may be used during query evaluation. * For example, zero times or very many times. * * Typically this hint is given when the URI is available at * compile-time, but it is used inside a conditional statement * whose branching can't be determined at compile time. */ MayUse, /** * Communicates that the URI will always be used at query * evaluation. */ WillUse }; typedef QExplicitlySharedDataPointer Ptr; inline ResourceLoader() {} virtual ~ResourceLoader(); /** * @short Calls to this function are generated by calls to the * fn:unparsed-text-available() function. * * @param uri A URI identifying the resource to retrieve. The URI is guaranteed * to be valid(QUrl::isValid() returns @c true) and to be absolute(QUrl::isRelative() * returns @c false). * @returns @c true if calling openUnparsedText() while passing @p uri will successfully load * the document. * @see XSL Transformations * (XSLT) Version 2.0, 16.2 Reading Text Files */ virtual bool isUnparsedTextAvailable(const QUrl &uri, const QString &encoding); /** * @short May be called by the compilation framework at compile time to report that an * unparsed text(plain text) file referenced by @p uri will be loaded at runtime. * * This function can be called an arbitrary amount of times for the same URI. How many times * it is called for a URI has no meaning(beyond the first call, that is). For what queries * the compilation framework can determine what always will be loaded is generally undefined. It * depends on factors such as how simple the query is what information that is statically * available and subsequently what optimizations that can apply. * * Calls to this function are generated by calls to the fn:unparsed-text() function. * * @param uri A URI identifying the resource to retrieve. The URI is guaranteed * to be valid(QUrl::isValid() returns @c true) and to be absolute(QUrl::isRelative() * returns @c false). * @see XSL Transformations * (XSLT) Version 2.0, 16.2 Reading Text Files * @returns * - @c null if no unparsed file can be loaded for @p uri * - The item type that the value loaded by @p uri will be an instance of. This is * typically @c xs:string */ virtual ItemType::Ptr announceUnparsedText(const QUrl &uri); /** * @short Calls to this function are generated by calls to the fn:unparsed-text() function. * * @param uri A URI identifying the resource to retrieve. The URI is guaranteed * to be valid(QUrl::isValid() returns @c true) and to be absolute(QUrl::isRelative() * returns @c false). * @param encoding the encoding to use. If empty, the user hasn't * expressed any encoding to use. * @see XSL Transformations * (XSLT) Version 2.0, 16.2 Reading Text Files * @returns * - @c null if no unparsed file can be loaded for @p uri * - An @c xs:string value(or subtype) containing the content of the file identified * by @p uri as text. Remember that its type must match the sequence type * returned by announceUnparsedText() */ virtual Item openUnparsedText(const QUrl &uri, const QString &encoding, const ReportContext::Ptr &context, const SourceLocationReflection *const where); /** * @short Calls to this function are generated by calls to the fn:document() * or fn:doc() function. * * @note This function is responsible for execution stability. Subsequent calls * to this function with the same URI should result in QXmlNodeModelIndex instances that have * the same identity. However, in some cases this stability is not of interest, see * the specification for details. * @param uri A URI identifying the resource to retrieve. The URI is guaranteed * to be valid(QUrl::isValid() returns @c true) and to be absolute(QUrl::isRelative() * returns @c false). * @see QXmlNodeModelIndex::identity() * @see XQuery 1.0 * and XPath 2.0 Functions and Operators, 15.5.4 fn:doc * @see XSL Transformations * (XSLT) Version 2.0, 16.1 Multiple Source Documents * @returns * - @c null if no document can be loaded for @p uri * - A QXmlNodeModelIndex representing the document identified by @p uri. Remember that the QXmlNodeModelIndex * must match the sequence type returned by announceDocument() */ virtual Item openDocument(const QUrl &uri, const ReportContext::Ptr &context); /** * @short May be called by the compilation framework at compile time to report that an * XML document referenced by @p uri will be loaded at runtime. * * This function can be called an arbitrary amount of times for the same URI, but different * @p usageHint values. How many times it is called for a URI has no meaning(beyond the first call, * that is). For what queries the compilation framework can determine what always will be * loaded is generally undefined. It * depends on factors such as the complexity of the query, what information that is statically * available and subsequently what optimizations that can be applied. * * Calls to this function are generated by calls to the fn:document() * or fn:doc() function. * * @param uri A URI identifying the resource to retrieve. The URI is guaranteed * to be valid(QUrl::isValid() returns @c true) and to be absolute(QUrl::isRelative() * returns @c false). * @param usageHint A hint to how the URI will be used. * @returns * - @c null if the ResourceLoader can determine at this stage that no document * referenced by @p uri will ever be possible to load. * - The appropriate sequence type if loading @p uri succeeds at runtime. This must be * CommonSequenceTypes::zeroOrOneDocument, CommonSequenceTypes::exactlyOneDocument or * a sequence type that is a sub type of it. * @see XQuery 1.0 * and XPath 2.0 Functions and Operators, 15.5.4 fn:doc * @see XSL Transformations * (XSLT) Version 2.0, 16.1 Multiple Source Documents */ virtual SequenceType::Ptr announceDocument(const QUrl &uri, const Usage usageHint); /** * @short Calls to this function are generated by calls to the fn:doc-available() function. * * @param uri A URI identifying the resource to retrieve. The URI is guaranteed * to be valid(QUrl::isValid() returns @c true) and to be absolute(QUrl::isRelative() * returns @c false). * @returns @c true if calling openDocument() while passing @p uri will successfully load * the document. * @see XQuery 1.0 * and XPath 2.0 Functions and Operators, 15.5.5 fn:doc-available * @see XSL Transformations * (XSLT) Version 2.0, 16.1 Multiple Source Documents */ virtual bool isDocumentAvailable(const QUrl &uri); /** * @short Calls to this function are generated by calls to the fn:collection() function. * * @param uri A URI identifying the resource to retrieve. The URI is guaranteed * to be valid(QUrl::isValid() returns @c true) and to be absolute(QUrl::isRelative() * returns @c false). * @see XQuery 1.0 * and XPath 2.0 Functions and Operators, 15.5.6 fn:collection * @returns * - @c null if no node collection can be loaded for @p uri * - An QAbstractXmlForwardIterator representing the content identified by @p uri. Remember that the content * of the QAbstractXmlForwardIterator must match the sequence type returned by announceCollection() */ virtual Item::Iterator::Ptr openCollection(const QUrl &uri); /** * @short May be called by the compilation framework at compile time to report that an * node collection referenced by @p uri will be loaded at runtime. * * This function can be called an arbitrary amount of times for the same URI. How many times * it is called for a URI has no meaning(beyond the first call, that is). For what queries * the compilation framework can determine what always will be loaded is generally undefined. It * depends on factors such as how simple the query is what information that is statically * available and subsequently what optimizations that can apply. * * Calls to this function are generated by calls to the fn:collection() function. * * @note This function is responsible for execution stability. Subsequent calls * to this function with the same URI should result in QXmlNodeModelIndex instances that have * the same identity. However, in some cases this stability is not of interest, see * the specification for details. * @param uri A URI identifying the resource to retrieve. The URI is guaranteed * to be valid(QUrl::isValid() returns @c true) and to be absolute(QUrl::isRelative() * returns @c false). * @returns * - @c null if the ResourceLoader can determine at this stage that no document * referenced by @p uri will ever be possible to load. * - The appropriate sequence type if loading @p uri succeeds at runtime. This must be * CommonSequenceTypes::zeroOrMoreNodes or a sequence type that is a sub type of it. * @see XQuery 1.0 * and XPath 2.0 Functions and Operators, 15.5.6 fn:collection */ virtual SequenceType::Ptr announceCollection(const QUrl &uri); /** * @short Asks to unload @p uri from its document pool, such that a * subsequent request will require a new read. * * The default implementation does nothing. */ virtual void clear(const QUrl &uri); }; } QT_END_NAMESPACE QT_END_HEADER #endif