xpathquery.h

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// © Copyright 2010 - 2016 BlackTopp Studios Inc.
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/*
 *
 * Software, Files, Libraries and all other items referenced in this clause refers only
 * to the contents of this file and associated documentation.
 *
 * Pugixml parser - version 1.0
 * --------------------------------------------------------
 * Copyright © 2006-2012, by Arseny Kapoulkine (arseny.kapoulkine@gmail.com)
 * Report bugs and download new versions at http://pugixml.org/
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 * This library is distributed under the MIT License. See notice at the end
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 * This work is based on the pugxml parser, which is:
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#ifndef _xmlxpathquery_h
#define _xmlxpathquery_h

/// @file
/// @brief The definition of the @ref Mezzanine::XML::XPathQuery .

#include "datatypes.h"
#include "XML/xmlenumerations.h"
#include "XML/xpathparseresult.h"



namespace Mezzanine
{
    namespace XML
    {
        // A compiled XPath query object
        class XPathNode;
        class XPathNodeSet;
        class XPathVariableSet;


        /// @brief A compiled XPath query object
        /// @details When you call @ref XML::Node::FindNodes with an expression string as an argument, a query object is created behind the scenes.
        /// A query object represents a compiled XPath expression. Query objects can be needed in the following circumstances: \n
        /// - You can precompile expressions to query objects to save compilation time if it becomes an issue; \n
        /// - You can use query objects to evaluate XPath expressions which result in booleans, numbers or strings; \n
        /// - You can get the type of expression value via query object. \n \n
        /// Query objects correspond to @ref XML::XPathQuery type. They are immutable and non-copyable: they are bound to the expression at creation
        /// 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
        /// to XML::XPathQuery in the container. \n \n
        /// To evaluate an XPath expression there are a few EvaluatedType functions. According to XPath specification, value of any type can be
        /// converted to boolean, number or string value, but no type other than node set can be converted to node set. Because of this,
        /// @ref XPathQuery::EvaluateBoole(), @ref XPathQuery::EvaluateNumber() and @ref XPathQuery::EvaluateString() always return a result,
        /// but EvaluateNodeSet results in an error if the return type is not node set.
        class MEZZ_LIB XPathQuery
        {
            private:
                /// @internal
                /// @brief Used to keep much of the implementation hidden from item including this.
                void* QueryImplementation;

                /// @internal
                /// @brief A cache for the result of the query
                XPathParseResult ResultCache ;

                #ifndef SWIG
                /// @internal
                /// @brief Used to convert this to a boolean value in a safe way
                typedef void (*unspecified_bool_type)(XPathQuery***);
                #endif

                /// @brief Private copy constructor to ensure non-copyable semantics.
                XPathQuery(const XPathQuery&);

                /// @brief Private assignment operator to ensure non-assignable semantics.
                XPathQuery& operator=(const XPathQuery&);

            public:
                /// @brief Construct a compiled object from XPath expression.
                /// @param query The query in the form of a c-string style char_t array.
                /// @param variables Any extra data the query might need, passing a null pointer simply omits passing any arguments.
                /// @throw Throws XPathException on compilation errors.
                explicit XPathQuery(const Char8* query, XPathVariableSet* variables = 0);

                // Destructor
                /// @brief Destructor
                ~XPathQuery();

                /// @brief Get query expression return Type.
                /// @return A XPathValueType.
                XPathValueType ReturnType() const;

                /// @brief Evaluate expression as boolean value in the specified context; performs Type conversion if necessary.
                /// @return A bool result of evaluating the expression.
                /// @throw If XML_NO_EXCEPTIONS is not defined (by default it is not defined), throws std::bad_alloc on out of memory errors.
                /// @param n The XPathNode that will serve as the context for the query.
                bool EvaluateBoole(const XPathNode& n) const;

                // Evaluate expression as double Value in the specified context; performs Type conversion if necessary.
                /// @brief Evaluate expression as double value in the specified context; performs Type conversion if necessary.
                /// @param n The XPathNode that will serve as the context for the query.
                /// @throw Throws std::bad_alloc on out of memory errors.
                /// @return A result as a double from evaluating the expression.
                double EvaluateNumber(const XPathNode& n) const;

                // Evaluate expression as string Value in the specified context; performs Type conversion if necessary.
                /// @brief Evaluate expression as string value in the specified context; performs Type conversion if necessary.
                /// @param n The XPathNode that will serve as the context for the query.
                /// @throw Throws std::bad_alloc on out of memory errors.
                /// @return A result as a String from evaluating the expression.
                String EvaluateString(const XPathNode& n) const;

                // Evaluate expression as string Value in the specified context; performs Type conversion if necessary.
                // At most capacity characters are written to the destination buffer, full Result size is returned (includes terminating zero).
                /// @brief Evaluate expression as string value in the specified context; performs Type conversion if necessary.
                /// @param buffer The place to store the c-style Character array
                /// @param capacity At most capacity characters are written to the destination buffer.
                /// @param n The XPathNode that with serve as the context for the query.
                /// @throw  std::bad_alloc on out of memory errors.
                /// @return Full result size is returned (includes terminating zero).
                size_t EvaluateString(Char8* buffer, size_t capacity, const XPathNode& n) const;

                // Evaluate expression as node set in the specified context.
                // throws XPathException on Type mismatch and std::bad_alloc on out of memory errors.

                /// @brief Evaluate expression as node set in the specified context.
                /// @param n The XPathNode that with serve as the context for the query.
                /// @return An XPathNodeSet.
                XPathNodeSet EvaluateNodeSet(const XPathNode& n) const;

                /// @brief Get parsing Result (used to get compilation errors when XML_NO_EXCEPTIONS is enabled)
                /// @return A const reference to an XPathParseResult.
                const XPathParseResult& Result() const;

                #ifndef SWIG
                /// @brief Used to convert this to a boolean value in a safe way
                /// @return Returns true if the internal data is set and false otherwise.
                operator unspecified_bool_type() const;
                #endif

                /// @brief Logical not operator, used a workaround for borland compiler.
                /// @return A bool that is the opposite of evaluatig this as a bool normally.
                bool operator!() const;
        };
    }
} // /namespace Mezzanine



#endif // Include guard


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