121 lines
3.0 KiB
C++
Executable File
121 lines
3.0 KiB
C++
Executable File
// file : odb/query.hxx
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// copyright : Copyright (c) 2009-2015 Code Synthesis Tools CC
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// license : GNU GPL v2; see accompanying LICENSE file
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#ifndef ODB_QUERY_HXX
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#define ODB_QUERY_HXX
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#include <odb/pre.hxx>
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#include <odb/forward.hxx>
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#include <odb/traits.hxx>
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namespace odb
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{
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// Table alias for type T and tag Tag.
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//
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// The alias_traits interface consists of two things: the table_name
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// static variable containing the name and, in case of a derived type
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// in a polymorphic hierarchy, the base_traits typedef. Note that the
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// same interface is exposed by object_traits, which is used when
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// we need straight tables instead of aliases.
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//
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//
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template <typename T, database_id DB, typename Tag>
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struct alias_traits;
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template <typename T, database_id DB>
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struct query_columns_base;
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template <typename T, database_id DB, typename A>
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struct query_columns;
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template <typename T, database_id DB, typename A>
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struct pointer_query_columns;
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// Object pointer syntax wrapper.
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//
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template <typename T>
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struct query_pointer
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{
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query_pointer ()
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{
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// For some reason GCC needs this dummy c-tor if we make a static
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// data member of this type const.
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}
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T*
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operator-> () const
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{
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return 0; // All members in T are static.
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}
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};
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// Query parameter decay traits.
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//
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template <typename T>
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struct decay_traits
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{
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typedef const T& type;
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static type
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instance ();
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};
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template <typename T, std::size_t N>
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struct decay_traits<T[N]>
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{
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typedef const T* type;
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// Use the pointer comparability as a proxy for data comparability.
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// Note that it is stricter than using element comparability (i.e.,
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// one can compare int to char but not int* to char*).
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//
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static type
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instance ();
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};
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// VC9 cannot handle certain cases of non-type arguments with default
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// values in template functions (e.g., database::query()). As a result,
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// we have to use the impl trick below instead of simply having kind
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// as a second template argument with a default value.
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//
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template <typename T, database_id DB, class_kind kind>
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struct query_selector_impl;
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template <typename T, database_id DB>
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struct query_selector_impl<T, DB, class_object>
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{
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typedef typename object_traits_impl<T, DB>::query_base_type base_type;
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typedef
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query_columns<T, DB, access::object_traits_impl<T, DB> >
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columns_type;
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};
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template <typename T, database_id DB>
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struct query_selector_impl<T, DB, class_view>
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{
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typedef typename view_traits_impl<T, DB>::query_base_type base_type;
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typedef typename view_traits_impl<T, DB>::query_columns columns_type;
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};
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template <typename T, database_id DB>
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struct query_selector: query_selector_impl<T, DB, class_traits<T>::kind>
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{
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};
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template <typename T,
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typename B = typename query_selector<T, id_common>::base_type>
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class query;
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namespace core
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{
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using odb::query;
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}
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}
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#include <odb/post.hxx>
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#endif // ODB_QUERY_HXX
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