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145 lines
3.3 KiB
Plaintext
145 lines
3.3 KiB
Plaintext
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## basic_policy
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### Synopsis
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Defined in <boost/openmethod/policies/basic_policy.hpp>.
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```c++
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namespace boost::openmethod {
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namespace policies {
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template<class Policy, class... Facets>
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struct basic_policy : virtual abstract_policy,
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virtual domain<Policy>,
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virtual Facets... {
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template<class Facet>
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static constexpr bool has_facet = /*unspecified*/;
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template<class NewPolicy>
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using fork = /*unspecified*/;
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template<class... MoreFacets>
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using add = /*unspecified*/;
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template<class Base, class Facet>
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using replace = /*unspecified*/;
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template<class Base>
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using remove = /*unspecified*/;
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};
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struct release : basic_policy<release, ...> {};
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struct debug : release::add<...> {};
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} // policies
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#ifdef NDEBUG
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using default_policy = policies::release;
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#else
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using default_policy = policies::debug;
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#endif
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} // boost::openmethod
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```
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### Description
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`basic_policy` implements a policy, which consists of a a collection of methods,
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classes, dispatch data, and facets, which specify how to obtain a pointer to a
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v-table from an object, how to report errors, whether to perform runtime sanity
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checks, etc.
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Some of these functionalities require static variables local to the policy.
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Forthis reason, `basic_policy` uses the CRTP pattern to provide ensure that two
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different policies - and the facets they contain - get their own copies of the
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static state.
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### Members
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#### has_facet
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```c++
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template<class Facet>
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static constexpr bool has_facet;
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```
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Evaluates to `true` if _Policy_ contains _Facet_.
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#### fork
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```c++
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template<class NewPolicy>
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using fork;
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```
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Creates a new policy from an existing one. _NewPolicy_, and the facets it
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contains, do not share static variables with the original _Policy_. The new
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policy does not retain any knowledge of the classes and methods registered in
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the original.
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#### add
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```c++
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template<class... MoreFacets>
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using add;
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```
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Creates a new policy by adding _MoreFacets_ to the original policy's collection
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of facets. The original policy and the new one share static variables.
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#### replace
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```c++
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template<class Base, class NewFacet>
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using replace;
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```
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Creates a new policy by replacing the facet in _Policy_ that derives from _Base_
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with _NewFacet_. It is not an error if _policy_ does not contain such a facet;
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in that case, the new policy contains the same facet as the original one.
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The original policy and the new one share static variables.
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#### remove
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```c++
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template<class Base>
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using remove;
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```
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Creates a new policy by removing the facet in _Policy_ that derives from _Base_.
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It is not an error if _policy_ does not contain such a facet; in that case, the
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new policy contains the same facet as the original one.
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The original policy and the new one share static variables.
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### Non-members
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#### release
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```c++
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struct release;
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```
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A policy that contains facet implementations `std_rtti`, `fast_perfect_hash`,
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`vptr_vector` and `vectored_error_handler`.
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#### debug
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```c++
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struct debug;
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```
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The `release` policy with additional facet implementations `runtime_checks`,
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`basic_error_output` and basic_trace_output.
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NOTE: `debug` extends `release` but it does not a fork it. Both policies use the
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same `domain`.
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#### default_policy
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An alias for `release` if `NDEBUG` is defined, and for `debug` otherwise.
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