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xpathquery.h
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43  * to the contents of this file and associated documentation.
44  *
45  * Pugixml parser - version 1.0
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56 #ifndef _xmlxpathquery_h
57 #define _xmlxpathquery_h
58 
59 /// @file
60 /// @brief The definition of the @ref Mezzanine::XML::XPathQuery .
61 
62 #include "datatypes.h"
63 #include "XML/xmlenumerations.h"
64 #include "XML/xpathparseresult.h"
65 
66 
67 
68 namespace Mezzanine
69 {
70  namespace XML
71  {
72  // A compiled XPath query object
73  class XPathNode;
74  class XPathNodeSet;
75  class XPathVariableSet;
76 
77 
78  /// @brief A compiled XPath query object
79  /// @details When you call @ref XML::Node::FindNodes with an expression string as an argument, a query object is created behind the scenes.
80  /// A query object represents a compiled XPath expression. Query objects can be needed in the following circumstances: \n
81  /// - You can precompile expressions to query objects to save compilation time if it becomes an issue; \n
82  /// - You can use query objects to evaluate XPath expressions which result in booleans, numbers or strings; \n
83  /// - You can get the type of expression value via query object. \n \n
84  /// Query objects correspond to @ref XML::XPathQuery type. They are immutable and non-copyable: they are bound to the expression at creation
85  /// time and can not be cloned. If you want to put query objects in a container, allocate them on heap via new operator and store pointers
86  /// to XML::XPathQuery in the container. \n \n
87  /// To evaluate an XPath expression there are a few EvaluatedType functions. According to XPath specification, value of any type can be
88  /// converted to boolean, number or string value, but no type other than node set can be converted to node set. Because of this,
89  /// @ref XPathQuery::EvaluateBoole(), @ref XPathQuery::EvaluateNumber() and @ref XPathQuery::EvaluateString() always return a result,
90  /// but EvaluateNodeSet results in an error if the return type is not node set.
92  {
93  private:
94  /// @internal
95  /// @brief Used to keep much of the implementation hidden from item including this.
96  void* QueryImplementation;
97 
98  /// @internal
99  /// @brief A cache for the result of the query
100  XPathParseResult ResultCache ;
101 
102  #ifndef SWIG
103  /// @internal
104  /// @brief Used to convert this to a boolean value in a safe way
105  typedef void (*unspecified_bool_type)(XPathQuery***);
106  #endif
107 
108  /// @brief Private copy constructor to ensure non-copyable semantics.
109  XPathQuery(const XPathQuery&);
110 
111  /// @brief Private assignment operator to ensure non-assignable semantics.
112  XPathQuery& operator=(const XPathQuery&);
113 
114  public:
115  /// @brief Construct a compiled object from XPath expression.
116  /// @param query The query in the form of a c-string style char_t array.
117  /// @param variables Any extra data the query might need, passing a null pointer simply omits passing any arguments.
118  /// @throw Throws XPathException on compilation errors.
119  explicit XPathQuery(const Char8* query, XPathVariableSet* variables = 0);
120 
121  // Destructor
122  /// @brief Destructor
123  ~XPathQuery();
124 
125  /// @brief Get query expression return Type.
126  /// @return A XPathValueType.
127  XPathValueType ReturnType() const;
128 
129  /// @brief Evaluate expression as boolean value in the specified context; performs Type conversion if necessary.
130  /// @return A bool result of evaluating the expression.
131  /// @throw If XML_NO_EXCEPTIONS is not defined (by default it is not defined), throws std::bad_alloc on out of memory errors.
132  /// @param n The XPathNode that will serve as the context for the query.
133  bool EvaluateBoole(const XPathNode& n) const;
134 
135  // Evaluate expression as double Value in the specified context; performs Type conversion if necessary.
136  /// @brief Evaluate expression as double value in the specified context; performs Type conversion if necessary.
137  /// @param n The XPathNode that will serve as the context for the query.
138  /// @throw Throws std::bad_alloc on out of memory errors.
139  /// @return A result as a double from evaluating the expression.
140  double EvaluateNumber(const XPathNode& n) const;
141 
142  // Evaluate expression as string Value in the specified context; performs Type conversion if necessary.
143  /// @brief Evaluate expression as string value in the specified context; performs Type conversion if necessary.
144  /// @param n The XPathNode that will serve as the context for the query.
145  /// @throw Throws std::bad_alloc on out of memory errors.
146  /// @return A result as a String from evaluating the expression.
147  String EvaluateString(const XPathNode& n) const;
148 
149  // Evaluate expression as string Value in the specified context; performs Type conversion if necessary.
150  // At most capacity characters are written to the destination buffer, full Result size is returned (includes terminating zero).
151  /// @brief Evaluate expression as string value in the specified context; performs Type conversion if necessary.
152  /// @param buffer The place to store the c-style Character array
153  /// @param capacity At most capacity characters are written to the destination buffer.
154  /// @param n The XPathNode that with serve as the context for the query.
155  /// @throw std::bad_alloc on out of memory errors.
156  /// @return Full result size is returned (includes terminating zero).
157  size_t EvaluateString(Char8* buffer, size_t capacity, const XPathNode& n) const;
158 
159  // Evaluate expression as node set in the specified context.
160  // throws XPathException on Type mismatch and std::bad_alloc on out of memory errors.
161 
162  /// @brief Evaluate expression as node set in the specified context.
163  /// @param n The XPathNode that with serve as the context for the query.
164  /// @return An XPathNodeSet.
165  XPathNodeSet EvaluateNodeSet(const XPathNode& n) const;
166 
167  /// @brief Get parsing Result (used to get compilation errors when XML_NO_EXCEPTIONS is enabled)
168  /// @return A const reference to an XPathParseResult.
169  const XPathParseResult& Result() const;
170 
171  #ifndef SWIG
172  /// @brief Used to convert this to a boolean value in a safe way
173  /// @return Returns true if the internal data is set and false otherwise.
174  operator unspecified_bool_type() const;
175  #endif
176 
177  /// @brief Logical not operator, used a workaround for borland compiler.
178  /// @return A bool that is the opposite of evaluatig this as a bool normally.
179  bool operator!() const;
180  };
181  }
182 } // /namespace Mezzanine
183 
184 
185 
186 #endif // Include guard
187 
188 
189 /*
190  *
191  * Software, Files, Libraries and all other items referenced in this clause refers only
192  * to the contents of this file and associated documentation.
193  *
194  * Copyright © 2006-2012 Arseny Kapoulkine
195  *
196  * Permission is hereby granted, free of charge, to any person
197  * obtaining a copy of this software and associated documentation
198  * files (the "Software"), to deal in the Software without
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202  * Software is furnished to do so, subject to the following
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204  *
205  * The above copyright notice and this permission notice shall be
206  * included in all copies or substantial portions of the Software.
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210  * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
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215  * OTHER DEALINGS IN THE SOFTWARE.
216  */
XPathValueType
XPathQuery return type.
A fixed sized collection of nodes that an XPathQuery can work on.
Definition: xpathnodeset.h:72
An XPath node which can store handles to a XML::Node or an XML::Attribute.
Definition: xpathnode.h:76
A compiled XPath query object.
Definition: xpathquery.h:91
All the definitions for datatypes as well as some basic conversion functions are defined here...
A set of XPath variables.
char Char8
A datatype to represent one character.
Definition: datatypes.h:169
Enumerations and constant values used primarily in the XML system but useful for interacting with it ...
Has all the classes for the XPath implementation.
#define MEZZ_LIB
Some platforms require special decorations to denote what is exported/imported in a share library...
The bulk of the engine components go in this namspace.
Definition: actor.cpp:56
std::string String
A datatype used to a series of characters.
Definition: datatypes.h:159