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✏️ Editing: function_base.hpp

// Boost.Function library

//  Copyright Douglas Gregor 2001-2006
//  Copyright Emil Dotchevski 2007
//  Use, modification and distribution is subject to the Boost Software License, Version 1.0.
//  (See accompanying file LICENSE_1_0.txt or copy at
//  http://www.boost.org/LICENSE_1_0.txt)

// For more information, see http://www.boost.org

#ifndef BOOST_FUNCTION_BASE_HEADER
#define BOOST_FUNCTION_BASE_HEADER

#include <boost/function/function_fwd.hpp>
#include <boost/function_equal.hpp>
#include <boost/core/typeinfo.hpp>
#include <boost/core/ref.hpp>
#include <boost/assert.hpp>
#include <boost/config.hpp>
#include <boost/config/workaround.hpp>
#include <stdexcept>
#include <string>
#include <memory>
#include <new>
#include <type_traits>

#if defined(BOOST_MSVC)
#   pragma warning( push )
#   pragma warning( disable : 4793 ) // complaint about native code generation
#   pragma warning( disable : 4127 ) // "conditional expression is constant"
#endif

// retained because used in a test
#define BOOST_FUNCTION_TARGET_FIX(x)

#define BOOST_FUNCTION_ENABLE_IF_NOT_INTEGRAL(Functor,Type) \
  typename std::enable_if< !std::is_integral<Functor>::value, Type>::type

namespace boost {
  namespace detail {
    namespace function {
      class X;

/**
       * A buffer used to store small function objects in
       * boost::function. It is a union containing function pointers,
       * object pointers, and a structure that resembles a bound
       * member function pointer.
       */
      union function_buffer_members
      {
        // For pointers to function objects
        typedef void* obj_ptr_t;
        mutable obj_ptr_t obj_ptr;

// For pointers to std::type_info objects
        struct type_t {
          // (get_functor_type_tag, check_functor_type_tag).
          const boost::core::typeinfo* type;

// Whether the type is const-qualified.
          bool const_qualified;
          // Whether the type is volatile-qualified.
          bool volatile_qualified;
        } type;

// For function pointers of all kinds
        typedef void (*func_ptr_t)();
        mutable func_ptr_t func_ptr;

#if defined(BOOST_MSVC) && BOOST_MSVC >= 1929
# pragma warning(push)
# pragma warning(disable: 5243)
#endif

// For bound member pointers
        struct bound_memfunc_ptr_t {
          void (X::*memfunc_ptr)(int);
          void* obj_ptr;
        } bound_memfunc_ptr;

#if defined(BOOST_MSVC) && BOOST_MSVC >= 1929
# pragma warning(pop)
#endif

// For references to function objects. We explicitly keep
        // track of the cv-qualifiers on the object referenced.
        struct obj_ref_t {
          mutable void* obj_ptr;
          bool is_const_qualified;
          bool is_volatile_qualified;
        } obj_ref;
      };

union BOOST_SYMBOL_VISIBLE function_buffer
      {
        // Type-specific union members
        mutable function_buffer_members members;

// To relax aliasing constraints
        mutable char data[sizeof(function_buffer_members)];
      };

// The operation type to perform on the given functor/function pointer
      enum functor_manager_operation_type {
        clone_functor_tag,
        move_functor_tag,
        destroy_functor_tag,
        check_functor_type_tag,
        get_functor_type_tag
      };

// Tags used to decide between different types of functions
      struct function_ptr_tag {};
      struct function_obj_tag {};
      struct member_ptr_tag {};
      struct function_obj_ref_tag {};

template<typename F>
      class get_function_tag
      {
        typedef typename std::conditional<std::is_pointer<F>::value,
                                   function_ptr_tag,
                                   function_obj_tag>::type ptr_or_obj_tag;

typedef typename std::conditional<std::is_member_pointer<F>::value,
                                   member_ptr_tag,
                                   ptr_or_obj_tag>::type ptr_or_obj_or_mem_tag;

typedef typename std::conditional<is_reference_wrapper<F>::value,
                                   function_obj_ref_tag,
                                   ptr_or_obj_or_mem_tag>::type or_ref_tag;

public:
        typedef or_ref_tag type;
      };

// The trivial manager does nothing but return the same pointer (if we
      // are cloning) or return the null pointer (if we are deleting).
      template<typename F>
      struct reference_manager
      {
        static inline void
        manage(const function_buffer& in_buffer, function_buffer& out_buffer,
               functor_manager_operation_type op)
        {
          switch (op) {
          case clone_functor_tag:
            out_buffer.members.obj_ref = in_buffer.members.obj_ref;
            return;

case move_functor_tag:
            out_buffer.members.obj_ref = in_buffer.members.obj_ref;
            in_buffer.members.obj_ref.obj_ptr = 0;
            return;

case destroy_functor_tag:
            out_buffer.members.obj_ref.obj_ptr = 0;
            return;

case check_functor_type_tag:
            {
              // Check whether we have the same type. We can add
              // cv-qualifiers, but we can't take them away.
              if (*out_buffer.members.type.type == BOOST_CORE_TYPEID(F)
                  && (!in_buffer.members.obj_ref.is_const_qualified
                      || out_buffer.members.type.const_qualified)
                  && (!in_buffer.members.obj_ref.is_volatile_qualified
                      || out_buffer.members.type.volatile_qualified))
                out_buffer.members.obj_ptr = in_buffer.members.obj_ref.obj_ptr;
              else
                out_buffer.members.obj_ptr = 0;
            }
            return;

case get_functor_type_tag:
            out_buffer.members.type.type = &BOOST_CORE_TYPEID(F);
            out_buffer.members.type.const_qualified = in_buffer.members.obj_ref.is_const_qualified;
            out_buffer.members.type.volatile_qualified = in_buffer.members.obj_ref.is_volatile_qualified;
            return;
          }
        }
      };

/**
       * Determine if boost::function can use the small-object
       * optimization with the function object type F.
       */
      template<typename F>
      struct function_allows_small_object_optimization
      {
        BOOST_STATIC_CONSTANT
          (bool,
           value = ((sizeof(F) <= sizeof(function_buffer) &&
                     (std::alignment_of<function_buffer>::value
                      % std::alignment_of<F>::value == 0))));
      };

template <typename F,typename A>
      struct functor_wrapper: public F, public A
      {
        functor_wrapper( F f, A a ):
          F(f),
          A(a)
        {
        }

functor_wrapper(const functor_wrapper& f) :
          F(static_cast<const F&>(f)),
          A(static_cast<const A&>(f))
        {
        }
      };

/**
       * The functor_manager class contains a static function "manage" which
       * can clone or destroy the given function/function object pointer.
       */
      template<typename Functor>
      struct functor_manager_common
      {
        typedef Functor functor_type;

// Function pointers
        static inline void
        manage_ptr(const function_buffer& in_buffer, function_buffer& out_buffer,
                functor_manager_operation_type op)
        {
          if (op == clone_functor_tag)
            out_buffer.members.func_ptr = in_buffer.members.func_ptr;
          else if (op == move_functor_tag) {
            out_buffer.members.func_ptr = in_buffer.members.func_ptr;
            in_buffer.members.func_ptr = 0;
          } else if (op == destroy_functor_tag)
            out_buffer.members.func_ptr = 0;
          else if (op == check_functor_type_tag) {
            if (*out_buffer.members.type.type == BOOST_CORE_TYPEID(Functor))
              out_buffer.members.obj_ptr = &in_buffer.members.func_ptr;
            else
              out_buffer.members.obj_ptr = 0;
          } else /* op == get_functor_type_tag */ {
            out_buffer.members.type.type = &BOOST_CORE_TYPEID(Functor);
            out_buffer.members.type.const_qualified = false;
            out_buffer.members.type.volatile_qualified = false;
          }
        }

// Function objects that fit in the small-object buffer.
        static inline void
        manage_small(const function_buffer& in_buffer, function_buffer& out_buffer,
                functor_manager_operation_type op)
        {
          if (op == clone_functor_tag) {
            const functor_type* in_functor =
              reinterpret_cast<const functor_type*>(in_buffer.data);
            new (reinterpret_cast<void*>(out_buffer.data)) functor_type(*in_functor);

} else if (op == move_functor_tag) {
              functor_type* f = reinterpret_cast<functor_type*>(in_buffer.data);
              new (reinterpret_cast<void*>(out_buffer.data)) functor_type(std::move(*f));
              f->~Functor();
          } else if (op == destroy_functor_tag) {
            // Some compilers (Borland, vc6, ...) are unhappy with ~functor_type.
             functor_type* f = reinterpret_cast<functor_type*>(out_buffer.data);
             (void)f; // suppress warning about the value of f not being used (MSVC)
             f->~Functor();
          } else if (op == check_functor_type_tag) {
             if (*out_buffer.members.type.type == BOOST_CORE_TYPEID(Functor))
              out_buffer.members.obj_ptr = in_buffer.data;
            else
              out_buffer.members.obj_ptr = 0;
          } else /* op == get_functor_type_tag */ {
            out_buffer.members.type.type = &BOOST_CORE_TYPEID(Functor);
            out_buffer.members.type.const_qualified = false;
            out_buffer.members.type.volatile_qualified = false;
          }
        }
      };

template<typename Functor>
      struct functor_manager
      {
      private:
        typedef Functor functor_type;

// Function pointers
        static inline void
        manager(const function_buffer& in_buffer, function_buffer& out_buffer,
                functor_manager_operation_type op, function_ptr_tag)
        {
          functor_manager_common<Functor>::manage_ptr(in_buffer,out_buffer,op);
        }

// Function objects that fit in the small-object buffer.
        static inline void
        manager(const function_buffer& in_buffer, function_buffer& out_buffer,
                functor_manager_operation_type op, std::true_type)
        {
          functor_manager_common<Functor>::manage_small(in_buffer,out_buffer,op);
        }

// Function objects that require heap allocation
        static inline void
        manager(const function_buffer& in_buffer, function_buffer& out_buffer,
                functor_manager_operation_type op, std::false_type)
        {
          if (op == clone_functor_tag) {
            // Clone the functor
            // GCC 2.95.3 gets the CV qualifiers wrong here, so we
            // can't do the static_cast that we should do.
            // jewillco: Changing this to static_cast because GCC 2.95.3 is
            // obsolete.
            const functor_type* f =
              static_cast<const functor_type*>(in_buffer.members.obj_ptr);
            functor_type* new_f = new functor_type(*f);
            out_buffer.members.obj_ptr = new_f;
          } else if (op == move_functor_tag) {
            out_buffer.members.obj_ptr = in_buffer.members.obj_ptr;
            in_buffer.members.obj_ptr = 0;
          } else if (op == destroy_functor_tag) {
            /* Cast from the void pointer to the functor pointer type */
            functor_type* f =
              static_cast<functor_type*>(out_buffer.members.obj_ptr);
            delete f;
            out_buffer.members.obj_ptr = 0;
          } else if (op == check_functor_type_tag) {
            if (*out_buffer.members.type.type == BOOST_CORE_TYPEID(Functor))
              out_buffer.members.obj_ptr = in_buffer.members.obj_ptr;
            else
              out_buffer.members.obj_ptr = 0;
          } else /* op == get_functor_type_tag */ {
            out_buffer.members.type.type = &BOOST_CORE_TYPEID(Functor);
            out_buffer.members.type.const_qualified = false;
            out_buffer.members.type.volatile_qualified = false;
          }
        }

// For function objects, we determine whether the function
        // object can use the small-object optimization buffer or
        // whether we need to allocate it on the heap.
        static inline void
        manager(const function_buffer& in_buffer, function_buffer& out_buffer,
                functor_manager_operation_type op, function_obj_tag)
        {
          manager(in_buffer, out_buffer, op,
                  std::integral_constant<bool, (function_allows_small_object_optimization<functor_type>::value)>());
        }

// For member pointers, we use the small-object optimization buffer.
        static inline void
        manager(const function_buffer& in_buffer, function_buffer& out_buffer,
                functor_manager_operation_type op, member_ptr_tag)
        {
          manager(in_buffer, out_buffer, op, std::true_type());
        }

public:
        /* Dispatch to an appropriate manager based on whether we have a
           function pointer or a function object pointer. */
        static inline void
        manage(const function_buffer& in_buffer, function_buffer& out_buffer,
               functor_manager_operation_type op)
        {
          typedef typename get_function_tag<functor_type>::type tag_type;
          if (op == get_functor_type_tag) {
            out_buffer.members.type.type = &BOOST_CORE_TYPEID(functor_type);
            out_buffer.members.type.const_qualified = false;
            out_buffer.members.type.volatile_qualified = false;
          } else {
            manager(in_buffer, out_buffer, op, tag_type());
          }
        }
      };

template<typename Functor, typename Allocator>
      struct functor_manager_a
      {
      private:
        typedef Functor functor_type;

using wrapper_allocator_type = typename std::allocator_traits<Allocator>::template rebind_alloc<functor_wrapper_type>;
          using wrapper_allocator_pointer_type = typename std::allocator_traits<wrapper_allocator_type>::pointer;

if (op == clone_functor_tag) {
            // Clone the functor
            // GCC 2.95.3 gets the CV qualifiers wrong here, so we
            // can't do the static_cast that we should do.
            const functor_wrapper_type* f =
              static_cast<const functor_wrapper_type*>(in_buffer.members.obj_ptr);
            wrapper_allocator_type wrapper_allocator(static_cast<Allocator const &>(*f));
            wrapper_allocator_pointer_type copy = wrapper_allocator.allocate(1);
            std::allocator_traits<wrapper_allocator_type>::construct(wrapper_allocator, copy, *f);

// Get back to the original pointer type
            functor_wrapper_type* new_f = static_cast<functor_wrapper_type*>(copy);
            out_buffer.members.obj_ptr = new_f;
          } else if (op == move_functor_tag) {
            out_buffer.members.obj_ptr = in_buffer.members.obj_ptr;
            in_buffer.members.obj_ptr = 0;
          } else if (op == destroy_functor_tag) {
            /* Cast from the void pointer to the functor_wrapper_type */
            functor_wrapper_type* victim =
              static_cast<functor_wrapper_type*>(in_buffer.members.obj_ptr);
            wrapper_allocator_type wrapper_allocator(static_cast<Allocator const &>(*victim));
            std::allocator_traits<wrapper_allocator_type>::destroy(wrapper_allocator, victim);
            wrapper_allocator.deallocate(victim,1);
            out_buffer.members.obj_ptr = 0;
          } else if (op == check_functor_type_tag) {
            if (*out_buffer.members.type.type == BOOST_CORE_TYPEID(Functor))
              out_buffer.members.obj_ptr = in_buffer.members.obj_ptr;
            else
              out_buffer.members.obj_ptr = 0;
          } else /* op == get_functor_type_tag */ {
            out_buffer.members.type.type = &BOOST_CORE_TYPEID(Functor);
            out_buffer.members.type.const_qualified = false;
            out_buffer.members.type.volatile_qualified = false;
          }
        }

// A type that is only used for comparisons against zero
      struct useless_clear_type {};

/**
       * Stores the "manager" portion of the vtable for a
       * boost::function object.
       */
      struct vtable_base
      {
        void (*manager)(const function_buffer& in_buffer,
                        function_buffer& out_buffer,
                        functor_manager_operation_type op);
      };
    } // end namespace function
  } // end namespace detail

/**
 * The function_base class contains the basic elements needed for the
 * function1, function2, function3, etc. classes. It is common to all
 * functions (and as such can be used to tell if we have one of the
 * functionN objects).
 */
class function_base
{
public:
  function_base() : vtable(0) { }

/** Determine if the function is empty (i.e., has no target). */
  bool empty() const { return !vtable; }

/** Retrieve the type of the stored function object, or type_id<void>()
      if this is empty. */
  const boost::core::typeinfo& target_type() const
  {
    if (!vtable) return BOOST_CORE_TYPEID(void);

detail::function::function_buffer type;
    get_vtable()->manager(functor, type, detail::function::get_functor_type_tag);
    return *type.members.type.type;
  }

template<typename Functor>
    Functor* target()
    {
      if (!vtable) return 0;

detail::function::function_buffer type_result;
      type_result.members.type.type = &BOOST_CORE_TYPEID(Functor);
      type_result.members.type.const_qualified = std::is_const<Functor>::value;
      type_result.members.type.volatile_qualified = std::is_volatile<Functor>::value;
      get_vtable()->manager(functor, type_result,
                      detail::function::check_functor_type_tag);
      return static_cast<Functor*>(type_result.members.obj_ptr);
    }

template<typename Functor>
    const Functor* target() const
    {
      if (!vtable) return 0;

detail::function::function_buffer type_result;
      type_result.members.type.type = &BOOST_CORE_TYPEID(Functor);
      type_result.members.type.const_qualified = true;
      type_result.members.type.volatile_qualified = std::is_volatile<Functor>::value;
      get_vtable()->manager(functor, type_result,
                      detail::function::check_functor_type_tag);
      // GCC 2.95.3 gets the CV qualifiers wrong here, so we
      // can't do the static_cast that we should do.
      return static_cast<const Functor*>(type_result.members.obj_ptr);
    }

template<typename F>
    typename std::enable_if< !std::is_function<F>::value, bool >::type
    contains(const F& f) const
    {
      if (const F* fp = this->template target<F>())
      {
        return function_equal(*fp, f);
      } else {
        return false;
      }
    }

template<typename Fn>
    typename std::enable_if< std::is_function<Fn>::value, bool >::type
    contains(Fn& f) const
    {
      typedef Fn* F;
      if (const F* fp = this->template target<F>())
      {
        return function_equal(*fp, &f);
      } else {
        return false;
      }
    }

public: // should be protected, but GCC 2.95.3 will fail to allow access
  detail::function::vtable_base* get_vtable() const {
    return reinterpret_cast<detail::function::vtable_base*>(
             reinterpret_cast<std::size_t>(vtable) & ~static_cast<std::size_t>(0x01));
  }

bool has_trivial_copy_and_destroy() const {
    return reinterpret_cast<std::size_t>(vtable) & 0x01;
  }

detail::function::vtable_base* vtable;
  mutable detail::function::function_buffer functor;
};

#if defined(BOOST_CLANG)
#   pragma clang diagnostic push
#   pragma clang diagnostic ignored "-Wweak-vtables"
#endif
/**
 * The bad_function_call exception class is thrown when a boost::function
 * object is invoked
 */
class BOOST_SYMBOL_VISIBLE bad_function_call : public std::runtime_error
{
public:
  bad_function_call() : std::runtime_error("call to empty boost::function") {}
};
#if defined(BOOST_CLANG)
#   pragma clang diagnostic pop
#endif

inline bool operator==(const function_base& f,
                       detail::function::useless_clear_type*)
{
  return f.empty();
}

inline bool operator!=(const function_base& f,
                       detail::function::useless_clear_type*)
{
  return !f.empty();
}

inline bool operator==(detail::function::useless_clear_type*,
                       const function_base& f)
{
  return f.empty();
}

inline bool operator!=(detail::function::useless_clear_type*,
                       const function_base& f)
{
  return !f.empty();
}

// Comparisons between boost::function objects and arbitrary function
// objects.

template<typename Functor>
  BOOST_FUNCTION_ENABLE_IF_NOT_INTEGRAL(Functor, bool)
  operator==(const function_base& f, Functor g)
  {
    if (const Functor* fp = f.template target<Functor>())
      return function_equal(*fp, g);
    else return false;
  }

template<typename Functor>
  BOOST_FUNCTION_ENABLE_IF_NOT_INTEGRAL(Functor, bool)
  operator==(Functor g, const function_base& f)
  {
    if (const Functor* fp = f.template target<Functor>())
      return function_equal(g, *fp);
    else return false;
  }

template<typename Functor>
  BOOST_FUNCTION_ENABLE_IF_NOT_INTEGRAL(Functor, bool)
  operator!=(const function_base& f, Functor g)
  {
    if (const Functor* fp = f.template target<Functor>())
      return !function_equal(*fp, g);
    else return true;
  }

template<typename Functor>
  BOOST_FUNCTION_ENABLE_IF_NOT_INTEGRAL(Functor, bool)
  operator!=(Functor g, const function_base& f)
  {
    if (const Functor* fp = f.template target<Functor>())
      return !function_equal(g, *fp);
    else return true;
  }

template<typename Functor>
  BOOST_FUNCTION_ENABLE_IF_NOT_INTEGRAL(Functor, bool)
  operator==(const function_base& f, reference_wrapper<Functor> g)
  {
    if (const Functor* fp = f.template target<Functor>())
      return fp == g.get_pointer();
    else return false;
  }

template<typename Functor>
  BOOST_FUNCTION_ENABLE_IF_NOT_INTEGRAL(Functor, bool)
  operator==(reference_wrapper<Functor> g, const function_base& f)
  {
    if (const Functor* fp = f.template target<Functor>())
      return g.get_pointer() == fp;
    else return false;
  }

template<typename Functor>
  BOOST_FUNCTION_ENABLE_IF_NOT_INTEGRAL(Functor, bool)
  operator!=(const function_base& f, reference_wrapper<Functor> g)
  {
    if (const Functor* fp = f.template target<Functor>())
      return fp != g.get_pointer();
    else return true;
  }

template<typename Functor>
  BOOST_FUNCTION_ENABLE_IF_NOT_INTEGRAL(Functor, bool)
  operator!=(reference_wrapper<Functor> g, const function_base& f)
  {
    if (const Functor* fp = f.template target<Functor>())
      return g.get_pointer() != fp;
    else return true;
  }

namespace detail {
  namespace function {
    inline bool has_empty_target(const function_base* f)
    {
      return f->empty();
    }

#if BOOST_WORKAROUND(BOOST_MSVC, <= 1310)
    inline bool has_empty_target(const void*)
    {
      return false;
    }
#else
    inline bool has_empty_target(...)
    {
      return false;
    }
#endif
  } // end namespace function
} // end namespace detail
} // end namespace boost

#undef BOOST_FUNCTION_ENABLE_IF_NOT_INTEGRAL

#if defined(BOOST_MSVC)
#   pragma warning( pop )
#endif

#endif // BOOST_FUNCTION_BASE_HEADER

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