bdlma_defaultdeleter.h

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/// @file bdlma_defaultdeleter.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bdlma_defaultdeleter.h                                             -*-C++-*-
#ifndef INCLUDED_BDLMA_DEFAULTDELETER
#define INCLUDED_BDLMA_DEFAULTDELETER
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bdlma_defaultdeleter bdlma_defaultdeleter
/// @brief  Provide a concrete default deleter w/optionally-supplied allocator.
/// @addtogroup bdl
/// @{
/// @addtogroup bdlma
/// @{
/// @addtogroup bdlma_defaultdeleter
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bdlma_defaultdeleter-purpose"> Purpose</a>
/// * <a href="#bdlma_defaultdeleter-classes"> Classes </a>
/// * <a href="#bdlma_defaultdeleter-description"> Description </a>
///   * <a href="#bdlma_defaultdeleter-usage"> Usage </a>
///     * <a href="#bdlma_defaultdeleter-example-1-basic-usage"> Example 1: Basic Usage </a>
///
/// # Purpose {#bdlma_defaultdeleter-purpose}
/// Provide a concrete default deleter w/optionally-supplied allocator.
///
/// # Classes {#bdlma_defaultdeleter-classes}
///
/// -   bdlma::DefaultDeleter: concrete default `bdema`-based deleter
///
/// @see  bslma_allocator, bdlma_deleter
///
/// # Description {#bdlma_defaultdeleter-description}
/// This component provides a default concrete implementation of
/// the `bdlma::Deleter` protocol:
/// @code
///                     ( bdlma::DefaultDeleter )
///                                |       ctor
///                                v
///                        ( bdlma::Deleter )
///                                        dtor
///                                        deleteObject
/// @endcode
/// Upon construction, a `bdlma::DefaultDeleter` is optionally supplied with a
/// `bdema`-style allocator.  If an allocator is not specified, the currently
/// installed default allocator is used instead.  The memory footprint of
/// objects that are subsequently deleted via calls to the `deleteObject` method
/// of the deleter will be returned to the allocator that was established at
/// construction.  Note that the allocator used to create the footprint of
/// objects passed to `deleteObject` *must* be the same allocator that is used
/// by the deleter.
///
/// ## Usage {#bdlma_defaultdeleter-usage}
///
///
/// This section illustrates intended use of this component.
///
/// ### Example 1: Basic Usage {#bdlma_defaultdeleter-example-1-basic-usage}
///
///
/// Suppose that we would like to transfer ownership of an object between
/// threads using `bsl::shared_ptr`.  For the sake of discussion, the type of
/// this object is `my_Obj` and we will suppose that it is created using a given
/// `basicAllocator`.  Note that we assume that `my_Obj` does not require an
/// allocator for any of its members:
/// @code
/// bslma::NewDeleteAllocator basicAllocator;
/// my_Obj *object = new(basicAllocator) my_Obj;
/// @endcode
/// Next, create a concrete deleter for `object` using the same allocator as was
/// used to allocate its footprint:
/// @code
/// bdlma::DefaultDeleter<my_Obj> deleter(&basicAllocator);
/// @endcode
/// Finally, create a shared pointer passing to it `object` and the address of
/// `deleter`:
/// @code
/// bsl::shared_ptr<my_Obj> handle(object, &deleter, &basicAllocator);
/// @endcode
/// Now the `handle` can be passed to another thread or enqueued efficiently.
/// When the reference count of `handle` goes to 0, `object` is automatically
/// deleted via the `deleteObject` method of `deleter`, which in turn will
/// invoke the destructor of `object`.  Note that since the type of the deleter
/// used to instantiate `handle` is `bdlma::Deleter<my_Obj>`, any kind of
/// deleter that implements this protocol can be passed.  Also note, on the
/// downside, that the lifetime of `deleter` must be longer than the lifetime of
/// all associated instances.
/// @}
/** @} */
/** @} */
 
/** @addtogroup bdl
 * @{
 */
/** @addtogroup bdlma
 * @{
 */
/** @addtogroup bdlma_defaultdeleter
 * @{
 */
 
#include <bdlscm_version.h>
 
#include <bdlma_deleter.h>
 
#include <bslma_allocator.h>
#include <bslma_default.h>
#include <bslma_usesbslmaallocator.h>
 
#include <bslmf_integralconstant.h>
 
#ifndef BDE_DONT_ALLOW_TRANSITIVE_INCLUDES
#include <bslalg_typetraits.h>
#endif // BDE_DONT_ALLOW_TRANSITIVE_INCLUDES
 
 
namespace bdlma {
 
                           // ====================
                           // class DefaultDeleter
                           // ====================
 
/// This `class` provides a default concrete implementation of the `Deleter`
/// protocol.  Instances of `DefaultDeleter<TYPE>` either use an allocator
/// optionally supplied at construction, or the currently installed default
/// allocator if an allocator is not provided.
///
/// See @ref bdlma_defaultdeleter 
template <class TYPE>
class DefaultDeleter : public Deleter<TYPE> {
 
    // DATA
    bslma::Allocator *d_allocator_p;  // memory allocator (held, *not* owned)
 
  private:
    // NOT IMPLEMENTED
    DefaultDeleter(const DefaultDeleter<TYPE>&);
    DefaultDeleter<TYPE>& operator=(const DefaultDeleter<TYPE>&);
 
  public:
    // CREATORS
 
    /// Create a default deleter.  Optionally specify a `basicAllocator`
    /// used to manage the memory footprint of objects passed to the
    /// `deleteObject` method.  If `basicAllocator` is 0, the currently
    /// installed default allocator is used.
    DefaultDeleter(bslma::Allocator *basicAllocator = 0);
 
    /// Destroy this default deleter.
    virtual ~DefaultDeleter();
 
    // MANIPULATORS
 
    /// Destroy the specified `instance` based on its static type and return
    /// its memory footprint to the appropriate memory manager.  
    /// 
    /// \pre The behavior is undefined   unless the memory for the footprint of
    /// `instance` was supplied by the same allocator as is used by this default deleter.  
    /// 
    /// \note Note that   this method does not destroy the deleter
    /// itself.
    virtual void deleteObject(TYPE *instance);
};
 
// ============================================================================
//                             INLINE DEFINITIONS
// ============================================================================
 
// CREATORS
template <class TYPE>
inline
DefaultDeleter<TYPE>::DefaultDeleter(bslma::Allocator *basicAllocator)
: d_allocator_p(bslma::Default::allocator(basicAllocator))
{
}
 
template <class TYPE>
DefaultDeleter<TYPE>::~DefaultDeleter()
{
}
 
// MANIPULATORS
template <class TYPE>
inline
void DefaultDeleter<TYPE>::deleteObject(TYPE *instance)
{
    d_allocator_p->deleteObject(instance);
}
 
}  // close package namespace
 
 
// TRAITS
 
 
namespace bslma {
 
template <class TYPE>
struct UsesBslmaAllocator<bdlma::DefaultDeleter<TYPE> > : bsl::true_type {};
 
}  // close namespace bslma
 
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2015 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */