bsltf_degeneratefunctor.h

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/// @file bsltf_degeneratefunctor.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bsltf_degeneratefunctor.h                                          -*-C++-*-
#ifndef INCLUDED_BSLTF_DEGENERATEFUNCTOR
#define INCLUDED_BSLTF_DEGENERATEFUNCTOR
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bsltf_degeneratefunctor bsltf_degeneratefunctor
/// @brief  Provide an awkward type to adapt a user-supplied functor.
/// @addtogroup bsl
/// @{
/// @addtogroup bsltf
/// @{
/// @addtogroup bsltf_degeneratefunctor
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bsltf_degeneratefunctor-purpose"> Purpose</a>
/// * <a href="#bsltf_degeneratefunctor-classes"> Classes </a>
/// * <a href="#bsltf_degeneratefunctor-description"> Description </a>
///   * <a href="#bsltf_degeneratefunctor-usage"> Usage </a>
///     * <a href="#bsltf_degeneratefunctor-example-1-tbd"> Example 1: TBD </a>
///
/// # Purpose {#bsltf_degeneratefunctor-purpose}
/// Provide an awkward type to adapt a user-supplied functor.
///
/// # Classes {#bsltf_degeneratefunctor-classes}
///
/// -  bsltf::DegenerateFunctor: awkward type that adapts a user-supplied functor
///
/// @see  bsltf_templatetestfacility
///
/// # Description {#bsltf_degeneratefunctor-description}
/// This component provides a functor adaptor, primarily for use
/// when testing templates that make use of Callable template parameters.  The
/// adaptor defined in this component provides an interface that is purposefully
/// as awkward as possible, yet should accepted by generic code, particularly
/// code conforming to the widest interpretation of the C++ standard library.
/// Many common operations that would be implicitly supplied, such as the
/// address-of operator and the comma operator, are explicitly disabled.  While
/// the adapter remains CopyConstructible so that it may be used as a member of
/// a class, such as a standard container, it is not CopyAssignable, and so
/// typically is not Swappable.  An additional boolean template argument
/// optionally creates an adapter that supports swapping.
///
/// ## Usage {#bsltf_degeneratefunctor-usage}
///
///
/// This section illustrates intended use of this component.
///
/// ### Example 1: TBD {#bsltf_degeneratefunctor-example-1-tbd}
///
///
/// @}
/** @} */
/** @} */
 
/** @addtogroup bsl
 * @{
 */
/** @addtogroup bsltf
 * @{
 */
/** @addtogroup bsltf_degeneratefunctor
 * @{
 */
 
#include <bslscm_version.h>
 
#include <bslmf_movableref.h>
 
#include <bsls_assert.h>
#include <bsls_util.h>
 
#include <new>
 
 
 
namespace bsltf {
 
                       // =======================
                       // class DegenerateFunctor
                       // =======================
 
/// This test class template adapts a CopyConstructible class to offer
/// a minimal or outright obstructive interface for testing generic code.
/// To support the testing of standard containers, this adapter will be
/// MoveConstructible, CopyConstructible, and nothrow Destructible as long
/// as the adapted `FUNCTOR` satisfies the same requirements.  This class
/// will further be Swappable if (the template parameter) `ENABLE_SWAP` is
/// `true` and the adapted `FUNCTOR` is MoveConstructible.  The (inherited)
/// function call operator should be the only other available method, no
/// other operation (e.g., the unary address-of operator) should be usable.
/// We take advantage of the fact that defining a copy constructor inhibits
/// the generation of a default constructor, and that constructors are not
/// inherited by a derived class.  `DegenerateFunctor` objects must be
/// created through either the copy constructor, or by wrapping a `FUNCTOR`
/// object through the static factory method of this class,
/// `cloneBaseObject`.
template <class FUNCTOR, bool ENABLE_SWAP = true>
class DegenerateFunctor : private FUNCTOR {
 
  private:
    // PRIVATE CREATORS
 
    /// Create a `DegenerateFunctor` wrapping a copy of the specified
    /// `base`.
    explicit DegenerateFunctor(const FUNCTOR& base);
 
  private:
    // NOT IMPLEMENTED
 
    /// Not implemented
    DegenerateFunctor& operator=(const DegenerateFunctor&); // = delete;
 
    /// not implemented
    void operator&();  // = delete;
 
    /// not implemented
    template<class T>
    void operator,(const T&); // = delete;
 
    /// not implemented
    template<class T>
    void operator,(T&); // = delete;
 
    /// Not implemented.  This method hides a frequently supplied member
    /// function that may be sniffed out by clever template code when it
    /// is declared in the base class.  When `ENABLE_SWAP` is `false`, we
    /// want to be sure that this class does not accidentally allow
    /// swapping through an unexpected back door.  When `ENABLE_SWAP` is
    /// `true`, we provide a differently named hook, to minimize the chance
    /// that a clever template library can sniff it out.
    template<class T>
    void swap(T&); // = delete;
 
  public:
    /// Create a DegenerateFunctor object wrapping a copy of the specified `base`.  
    /// 
    /// \note Note that   this method is supplied so that the only
    /// publicly accessible constructor is the copy constructor.
    static DegenerateFunctor cloneBaseObject(const FUNCTOR& base);
 
    // CREATORS
 
    /// Create a `DegenerateFunctor` having the same value the specified
    /// `original`.
    DegenerateFunctor(const DegenerateFunctor& original);
 
    /// Create a `DegenerateFunctor` having the same value the specified
    /// `original, and leave `original' in an unspecified (but valid) state.
    DegenerateFunctor(bslmf::MovableRef<DegenerateFunctor> original);
 
    // MANIPULATORS
 
    /// Expose the overloaded function call operator from the parameterizing
    /// class `FUNCTOR`.
    using FUNCTOR::operator();
 
    /// Swap the wrapped `FUNCTOR` object, by move-constructing a temporary
    /// object from the specified `*other`, then alternately destroying and
    /// in-place move-constructing new values for each of `*other` and `*this`.  
    /// 
    /// \note Note that   this function is deliberately *not* named `swap`
    /// as some "clever" template libraries may try to call a member-swap
    /// function when they can find it, and ADL-swap is not available.  Also
    /// note that this overload is needed only so that the ADL-enabling
    /// free-function `swap` can be defined, as the native std library
    /// `std::swap` function will not accept this class (with its deliberate
    /// degenerate nature) on AIX, or on Windows with Visual C++ prior to
    /// VC2010.
    void exchangeValues(DegenerateFunctor *other);
};
 
/// Exchange the values of the specified `lhs` and `rhs` objects.
template <class FUNCTOR>
void swap(DegenerateFunctor<FUNCTOR, true>& lhs,
          DegenerateFunctor<FUNCTOR, true>& rhs);
 
 
// ============================================================================
//                  INLINE AND TEMPLATE FUNCTION IMPLEMENTATIONS
// ============================================================================
 
                       // -----------------------
                       // class DegenerateFunctor
                       // -----------------------
 
// CREATORS
template <class FUNCTOR, bool ENABLE_SWAP>
inline
DegenerateFunctor<FUNCTOR, ENABLE_SWAP>::DegenerateFunctor(const FUNCTOR& base)
: FUNCTOR(base)
{
}
 
template <class FUNCTOR, bool ENABLE_SWAP>
inline
DegenerateFunctor<FUNCTOR, ENABLE_SWAP>::DegenerateFunctor(
                                             const DegenerateFunctor& original)
: FUNCTOR(original)
{
}
 
template <class FUNCTOR, bool ENABLE_SWAP>
inline
DegenerateFunctor<FUNCTOR, ENABLE_SWAP>::DegenerateFunctor(
                                 bslmf::MovableRef<DegenerateFunctor> original)
: FUNCTOR(bslmf::MovableRefUtil::move(static_cast<FUNCTOR&>(original)))
{
}
 
template <class FUNCTOR, bool ENABLE_SWAP>
inline
DegenerateFunctor<FUNCTOR, ENABLE_SWAP>
DegenerateFunctor<FUNCTOR, ENABLE_SWAP>::cloneBaseObject(const FUNCTOR& base)
{
    return DegenerateFunctor(base);
}
 
template <class FUNCTOR, bool ENABLE_SWAP>
inline
void
DegenerateFunctor<FUNCTOR, ENABLE_SWAP>::exchangeValues(
                                                      DegenerateFunctor *other)
{
    BSLS_ASSERT_SAFE(other);
 
    DegenerateFunctor temp(bslmf::MovableRefUtil::move(*other));
    other->~DegenerateFunctor();
    ::new((void *)other) DegenerateFunctor(bslmf::MovableRefUtil::move(*this));
    this->~DegenerateFunctor();
    ::new((void *)this) DegenerateFunctor(bslmf::MovableRefUtil::move(temp));
}
 
}  // close package namespace
 
template <class FUNCTOR>
inline
void bsltf::swap(DegenerateFunctor<FUNCTOR, true>& lhs,
                 DegenerateFunctor<FUNCTOR, true>& rhs)
{
    lhs.exchangeValues(bsls::Util::addressOf(rhs));
}
 
 
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2013 Bloomberg Finance L.P.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
// ----------------------------- END-OF-FILE ----------------------------------
 
/** @} */
/** @} */
/** @} */