summaryrefslogtreecommitdiff
path: root/src/xmlpatterns/data/qresourceloader_p.h
blob: 4ed43421d4fd1d6f3271a61bec71ef77701cae00 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
/****************************************************************************
**
** Copyright (C) 2011 Nokia Corporation and/or its subsidiary(-ies).
** All rights reserved.
** Contact: Nokia Corporation (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 Technology Preview License Agreement accompanying
** this package.
**
** 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.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain additional
** rights.  These rights are described in the Nokia Qt LGPL Exception
** version 1.1, included in the file LGPL_EXCEPTION.txt in this package.
**
** If you have questions regarding the use of this file, please contact
** Nokia at qt-info@nokia.com.
**
**
**
**
**
**
**
**
** $QT_END_LICENSE$
**
****************************************************************************/

//
//  W A R N I N G
//  -------------
//
// This file is not part of the Qt API.  It exists purely as an
// implementation detail.  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 <tt>fn:document()</tt> and <tt>fn:unparsed-text()</tt>;
     * and node collections, requested via <tt>fn:collection()</tt>. 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 <frans.englich@nokia.com>
     */
    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 cannot be determined at compile time.
             */
            MayUse,

            /**
             * Communicates that the URI will always be used at query
             * evaluation.
             */
            WillUse
        };

        typedef QExplicitlySharedDataPointer<ResourceLoader> Ptr;
        inline ResourceLoader() {}
        virtual ~ResourceLoader();

        /**
         * @short Calls to this function are generated by calls to the
         * <tt>fn:unparsed-text-available()</tt> 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 <a href="http://www.w3.org/TR/xslt20/#unparsed-text">XSL Transformations
         * (XSLT) Version 2.0, 16.2 Reading Text Files</a>
         */
        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 <tt>fn:unparsed-text()</tt> 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 <a href="http://www.w3.org/TR/xslt20/#unparsed-text">XSL Transformations
         * (XSLT) Version 2.0, 16.2 Reading Text Files</a>
         * @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 <tt>fn:unparsed-text()</tt> 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 <a href="http://www.w3.org/TR/xslt20/#unparsed-text">XSL Transformations
         * (XSLT) Version 2.0, 16.2 Reading Text Files</a>
         * @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 <tt>fn:document()</tt>
         * or <tt>fn:doc()</tt> 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 <a href="http://www.w3.org/TR/xpath-functions/#func-doc">XQuery 1.0
         * and XPath 2.0 Functions and Operators, 15.5.4 fn:doc</a>
         * @see <a href="http://www.w3.org/TR/xslt20/#document">XSL Transformations
         * (XSLT) Version 2.0, 16.1 Multiple Source Documents</a>
         * @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 <tt>fn:document()</tt>
         * or <tt>fn:doc()</tt> 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 <a href="http://www.w3.org/TR/xpath-functions/#func-doc">XQuery 1.0
         * and XPath 2.0 Functions and Operators, 15.5.4 fn:doc</a>
         * @see <a href="http://www.w3.org/TR/xslt20/#document">XSL Transformations
         * (XSLT) Version 2.0, 16.1 Multiple Source Documents</a>
         */
        virtual SequenceType::Ptr announceDocument(const QUrl &uri, const Usage usageHint);

        /**
         * @short Calls to this function are generated by calls to the <tt>fn:doc-available()</tt> 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 <a href="http://www.w3.org/TR/xpath-functions/#func-doc-available">XQuery 1.0
         * and XPath 2.0 Functions and Operators, 15.5.5 fn:doc-available</a>
         * @see <a href="http://www.w3.org/TR/xslt20/#document">XSL Transformations
         * (XSLT) Version 2.0, 16.1 Multiple Source Documents</a>
         */
        virtual bool isDocumentAvailable(const QUrl &uri);

        /**
         * @short Calls to this function are generated by calls to the <tt>fn:collection()</tt> 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 <a href="http://www.w3.org/TR/xpath-functions/#func-collection">XQuery 1.0
         * and XPath 2.0 Functions and Operators, 15.5.6 fn:collection</a>
         * @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 <tt>fn:collection()</tt> 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 <a href="http://www.w3.org/TR/xpath-functions/#func-collection">XQuery 1.0
         * and XPath 2.0 Functions and Operators, 15.5.6 fn:collection</a>
         */
        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