forked from boostorg/function
Initial comit
[SVN r10368]
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Beman Dawes
416
include/boost/function/function_base.hpp
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416
include/boost/function/function_base.hpp
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// Copyright (C) 2001 Doug Gregor (gregod@cs.rpi.edu)
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//
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// Permission to copy, use, sell and distribute this software is granted
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// provided this copyright notice appears in all copies.
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// Permission to modify the code and to distribute modified code is granted
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// provided this copyright notice appears in all copies, and a notice
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// that the code was modified is included with the copyright notice.
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//
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// This software is provided "as is" without express or implied warranty,
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// and with no claim as to its suitability for any purpose.
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// For more information, see http://www.boost.org
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#ifndef BOOST_FUNCTION_BASE_HEADER
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#define BOOST_FUNCTION_BASE_HEADER
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#include <string>
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#include <stdexcept>
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#include <memory>
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#include <boost/config.hpp>
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#include <boost/type_traits.hpp>
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// Microsoft Visual C++ 6.0sp5 has lots of quirks
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#ifdef BOOST_MSVC
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# define BOOST_MSVC_INCLUDE(x) x
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#else
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# define BOOST_MSVC_INCLUDE(x)
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#endif
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namespace boost {
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namespace detail {
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namespace function {
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/*
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* The IF implementation is temporary code. When a Boost metaprogramming
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* library is introduced, Boost.Function will use it instead.
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*/
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namespace intimate {
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struct SelectThen
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{
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template<typename Then, typename Else>
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struct Result
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{
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typedef Then RET;
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};
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};
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struct SelectElse
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{
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template<typename Then, typename Else>
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struct Result
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{
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typedef Else RET;
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};
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};
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template<bool Condition>
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struct Selector
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{
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typedef SelectThen RET;
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};
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template<>
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struct Selector<false>
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{
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typedef SelectElse RET;
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};
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} // end namespace intimate
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template<bool Condition, typename Then, typename Else>
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struct IF
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{
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typedef typename intimate::Selector<Condition>::RET select;
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typedef typename select::template Result<Then,Else>::RET RET;
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typedef RET type;
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};
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/**
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* A union of a function pointer and a void pointer. This is necessary
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* because 5.2.10/6 allows reinterpret_cast<> to safely cast between
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* function pointer types and 5.2.9/10 allows static_cast<> to safely
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* cast between a void pointer and an object pointer. But it is not legal
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* to cast between a function pointer and a void* (in either direction),
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* so function requires a union of the two. */
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union any_pointer
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{
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void* obj_ptr;
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void (*func_ptr)();
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explicit any_pointer(void* p) : obj_ptr(p) {}
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explicit any_pointer(void (*p)()) : func_ptr(p) {}
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};
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/**
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* The unusable class is a placeholder for unused function arguments
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* It is also completely unusable except that it constructable from
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* anything. This helps compilers without partial specialization to
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* handle Boost.Function objects returning void.
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*/
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struct unusable
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{
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unusable() {}
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template<typename T> unusable(const T&) {}
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};
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/* Determine the return type. This supports compilers that do not support
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* void returns or partial specialization by silently changing the return
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* type to "unusable".
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*/
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template<typename T> struct function_return_type { typedef T type; };
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#ifdef BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION
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template<>
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struct function_return_type<void>
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{
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typedef unusable type;
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};
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#endif /* BOOST_NO_TEMPLATE_PARTIAL_SPECIALIZATION */
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// The operation type to perform on the given functor/function pointer
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enum functor_manager_operation_type { clone_functor, destroy_functor };
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// Tags used to decide between function and function object pointers.
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struct function_ptr_tag {};
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struct function_obj_tag {};
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#ifndef BOOST_FUNCTION_USE_VIRTUAL_FUNCTIONS
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/**
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* The functor_manager class contains a static function "manage" which
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* can clone or destroy the given function/function object pointer.
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*/
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template<typename Functor, typename Allocator>
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struct functor_manager
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{
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private:
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typedef Functor functor_type;
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# ifndef BOOST_NO_STD_ALLOCATOR
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typedef typename Allocator::template rebind<functor_type>::other
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allocator_type;
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typedef typename allocator_type::pointer pointer_type;
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# else
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typedef functor_type* pointer_type;
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# endif // BOOST_NO_STD_ALLOCATOR
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// For function pointers, the manager is trivial
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static inline any_pointer
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manager(any_pointer function_ptr, functor_manager_operation_type op,
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function_ptr_tag)
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{
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if (op == clone_functor)
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return function_ptr;
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else
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return any_pointer(static_cast<void (*)()>(0));
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}
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// For function object pointers, we clone the pointer to each
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// function has its own version.
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static inline any_pointer
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manager(any_pointer function_obj_ptr,
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functor_manager_operation_type op,
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function_obj_tag)
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{
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# ifndef BOOST_NO_STD_ALLOCATOR
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allocator_type allocator;
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# endif // BOOST_NO_STD_ALLOCATOR
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if (op == clone_functor) {
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functor_type* f =
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static_cast<functor_type*>(function_obj_ptr.obj_ptr);
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// Clone the functor
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# ifndef BOOST_NO_STD_ALLOCATOR
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pointer_type copy = allocator.allocate(1);
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allocator.construct(copy, *f);
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// Get back to the original pointer type
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functor_type* new_f = static_cast<functor_type*>(copy);
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# else
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functor_type* new_f = new functor_type(*f);
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# endif // BOOST_NO_STD_ALLOCATOR
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return any_pointer(static_cast<void*>(new_f));
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}
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else {
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/* Cast from the void pointer to the functor pointer type */
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functor_type* f =
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reinterpret_cast<functor_type*>(function_obj_ptr.obj_ptr);
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# ifndef BOOST_NO_STD_ALLOCATOR
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/* Cast from the functor pointer type to the allocator's pointer
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type */
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pointer_type victim = static_cast<pointer_type>(f);
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// Destroy and deallocate the functor
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allocator.destroy(victim);
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allocator.deallocate(victim, 1);
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# else
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delete f;
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# endif // BOOST_NO_STD_ALLOCATOR
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return any_pointer(static_cast<void*>(0));
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}
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}
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public:
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/* Dispatch to an appropriate manager based on whether we have a
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function pointer or a function object pointer. */
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static any_pointer
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manage(any_pointer functor_ptr, functor_manager_operation_type op)
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{
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typedef typename IF<(is_pointer<functor_type>::value),
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function_ptr_tag,
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function_obj_tag>::RET tag_type;
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return manager(functor_ptr, op, tag_type());
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}
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};
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#endif // BOOST_FUNCTION_USE_VIRTUAL_FUNCTIONS
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// value=1 if the given type is not "unusable"
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template<typename T>
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struct count_if_used
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{
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BOOST_STATIC_CONSTANT(int, value = 1);
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};
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// value=0 for unusable types
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template<>
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struct count_if_used<unusable>
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{
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BOOST_STATIC_CONSTANT(int, value = 0);
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};
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// Count the number of arguments (from the given set) which are not
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// "unusable" (therefore, count those arguments that are used).
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template<typename T1, typename T2, typename T3, typename T4,
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typename T5, typename T6, typename T7, typename T8,
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typename T9, typename T10>
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struct count_used_args
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{
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BOOST_STATIC_CONSTANT(int, value =
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(count_if_used<T1>::value +
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count_if_used<T2>::value +
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count_if_used<T3>::value +
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count_if_used<T4>::value +
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count_if_used<T5>::value +
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count_if_used<T6>::value +
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count_if_used<T7>::value +
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count_if_used<T8>::value +
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count_if_used<T9>::value +
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count_if_used<T10>::value));
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};
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} // end namespace function
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} // end namespace detail
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/**
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* The function_base class contains the basic elements needed for the
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* function1, function2, function3, etc. classes. It is common to all
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* functions (and as such can be used to tell if we have one of the
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* functionN objects).
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*/
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class function_base
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{
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#ifdef BOOST_FUNCTION_USE_VIRTUAL_FUNCTIONS
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public:
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function_base() : impl(0) {}
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bool empty() const { return impl == 0; }
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protected:
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void* impl; // Derived class is responsible for knowing the real type
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#else
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public:
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function_base() : manager(0), functor(static_cast<void*>(0)) {}
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// Is this function empty?
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bool empty() const { return !manager; }
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protected:
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detail::function::any_pointer (*manager)(
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detail::function::any_pointer,
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detail::function::functor_manager_operation_type);
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detail::function::any_pointer functor;
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#endif // BOOST_FUNCTION_USE_VIRTUAL_FUNCTIONS
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#ifndef BOOST_WEAK_CONVERSION_OPERATORS
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private:
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struct dummy {
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void nonnull() {};
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};
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typedef void (dummy::*safe_bool)();
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public:
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operator safe_bool () const
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{
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return (this->empty())? 0 : &dummy::nonnull;
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}
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#else
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public:
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operator bool() const { return !this->empty(); }
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#endif // BOOST_WEAK_CONVERSION_OPERATORS
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};
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/* Poison comparison between Boost.Function objects (because it is
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* meaningless). The comparisons would otherwise be allowed because of the
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* conversion required to allow syntax such as:
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* boost::function<int, int> f;
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* if (f) { f(5); }
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*/
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void operator==(const function_base&, const function_base&);
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void operator!=(const function_base&, const function_base&);
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namespace detail {
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namespace function {
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/**
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* Determine if the given target is empty.
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*/
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// Fallback - assume target is not empty
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inline bool has_empty_target(...)
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{
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return false;
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}
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// If the target is a 'function', query the empty() method
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inline bool has_empty_target(const function_base* af)
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{
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return af->empty();
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}
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// If the target is a 'function', query the empty() method
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inline bool has_empty_target(const function_base& af)
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{
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return af.empty();
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}
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// A function pointer is empty if it is null
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template<typename R>
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inline bool has_empty_target(R (*f)())
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{
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return f == 0;
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}
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template<typename R, typename T1>
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inline bool has_empty_target(R (*f)(T1))
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{
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return f == 0;
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}
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template<typename R, typename T1, typename T2>
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inline bool has_empty_target(R (*f)(T1, T2))
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{
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return f == 0;
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}
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template<typename R, typename T1, typename T2, typename T3>
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inline bool has_empty_target(R (*f)(T1, T2, T3))
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{
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return f == 0;
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}
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template<typename R, typename T1, typename T2, typename T3, typename T4>
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inline bool has_empty_target(R (*f)(T1, T2, T3, T4))
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{
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return f == 0;
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}
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template<typename R, typename T1, typename T2, typename T3, typename T4,
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typename T5>
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inline bool has_empty_target(R (*f)(T1, T2, T3, T4, T5))
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{
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return f == 0;
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}
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template<typename R, typename T1, typename T2, typename T3, typename T4,
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typename T5, typename T6>
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inline bool has_empty_target(R (*f)(T1, T2, T3, T4, T5, T6))
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{
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return f == 0;
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}
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template<typename R, typename T1, typename T2, typename T3, typename T4,
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typename T5, typename T6, typename T7>
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inline bool has_empty_target(R (*f)(T1, T2, T3, T4, T5, T6, T7))
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{
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return f == 0;
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}
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template<typename R, typename T1, typename T2, typename T3, typename T4,
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typename T5, typename T6, typename T7, typename T8>
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inline bool has_empty_target(R (*f)(T1, T2, T3, T4, T5, T6, T7, T8))
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{
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return f == 0;
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}
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template<typename R, typename T1, typename T2, typename T3, typename T4,
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typename T5, typename T6, typename T7, typename T8, typename T9>
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inline bool has_empty_target(R (*f)(T1, T2, T3, T4, T5, T6, T7, T8, T9))
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{
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return f == 0;
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}
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} // end namespace function
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} // end namespace detail
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// The default function policy is to do nothing before and after the call.
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struct empty_function_policy
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{
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inline void precall(const function_base*) {}
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inline void postcall(const function_base*) {}
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};
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// The default function mixin costs nothing
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struct empty_function_mixin {};
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}
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#endif // BOOST_FUNCTION_BASE_HEADER
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