bslma_deleterhelper.h

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/// @file bslma_deleterhelper.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bslma_deleterhelper.h                                              -*-C++-*-
#ifndef INCLUDED_BSLMA_DELETERHELPER
#define INCLUDED_BSLMA_DELETERHELPER
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bslma_deleterhelper bslma_deleterhelper
/// @brief  Provide namespace for functions used to delete objects.
/// @addtogroup bsl
/// @{
/// @addtogroup bslma
/// @{
/// @addtogroup bslma_deleterhelper
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bslma_deleterhelper-purpose"> Purpose</a>
/// * <a href="#bslma_deleterhelper-classes"> Classes </a>
/// * <a href="#bslma_deleterhelper-description"> Description </a>
///   * <a href="#bslma_deleterhelper-usage"> Usage </a>
///
/// # Purpose {#bslma_deleterhelper-purpose}
/// Provide namespace for functions used to delete objects.
///
/// # Classes {#bslma_deleterhelper-classes}
///
/// -  bslma::DeleterHelper: non-primitive functions for deleting objects
///
/// @see  bslma_rawdeleterguard, bslmf_ispolymporphic
///
/// # Description {#bslma_deleterhelper-description}
/// This component provides non-primitive procedures used to delete
/// objects of parameterized `TYPE` by first calling the destructor of the
/// object, and then freeing the memory footprint of the object using a
/// parameterized `ALLOCATOR` (allocator or pool) provided as a second argument.
/// The "raw" method (`deleteObjectRaw`) should be used only if we are sure that
/// the supplied object is **not** of a type that is a secondary base class --
/// i.e., the object's address is (numerically) the same as when it was
/// originally dispensed by `ALLOCATOR`.  The non-"raw" `deleteObject` has no
/// such restriction.  Note that this component will fail to compile when
/// instantiated for a class that gives a false-positive for the type trait
/// `bsl::is_polymorphic`.  See the @ref bslmf_ispolymporphic  component for more
/// details.
///
/// ## Usage {#bslma_deleterhelper-usage}
///
///
/// The following `my_RawDeleterGuard` class defines a guard that
/// unconditionally deletes a managed object upon destruction.  Via the
/// `deleteObjectRaw` method supplied by this component, the guard's destructor
/// first destroys the managed object, then deallocates the footprint of the
/// object.  The declaration of `my_RawDeleterGuard` follows:
/// @code
/// /// This class implements a guard that unconditionally deletes a managed
/// /// object upon destruction by first invoking the object's destructor,
/// /// and then invoking the `deallocate` method of an allocator (or pool)
/// /// of parameterized `ALLOCATOR` type supplied at construction.
/// template <class TYPE, class ALLOCATOR>
/// class my_RawDeleterGuard {
///
///     // DATA
///     TYPE      *d_object_p;     // managed object
///     ALLOCATOR *d_allocator_p;  // allocator or pool (held, not owned)
///
///     // NOT IMPLEMENTED
///     my_RawDeleterGuard(const my_RawDeleterGuard&);
///     my_RawDeleterGuard& operator=(const my_RawDeleterGuard&);
///
///   public:
///     // CREATORS
///
///     /// Create a raw deleter guard that unconditionally manages the
///     /// specified `object`, and that uses the specified `allocator` to
///     /// delete `object` upon the destruction of this guard.  The
///     /// behavior is undefined unless `object` and `allocator` are
///     /// non-zero, and `allocator` supplied the memory for `object`.
///     /// Note that `allocator` must remain valid throughout the lifetime
///     /// of this guard.
///     my_RawDeleterGuard(TYPE *object, ALLOCATOR *allocator);
///
///     /// Destroy this raw deleter guard and delete the object it manages
///     /// by first invoking the destructor of the (managed) object, and
///     /// then invoking the `deallocate` method of the allocator (or pool)
///     /// that was supplied with the object at construction.
///     ~my_RawDeleterGuard();
/// };
/// @endcode
/// The `deleteObjectRaw` method is used in the destructor as follows:
/// @code
/// template <class TYPE, class ALLOCATOR>
/// inline
/// my_RawDeleterGuard<TYPE, ALLOCATOR>::~my_RawDeleterGuard()
/// {
///     bslma::DeleterHelper::deleteObjectRaw(d_object_p, d_allocator_p);
/// }
/// @endcode
/// Note that we have denoted our guard to be a "raw" guard in keeping with this
/// use of `deleteObjectRaw` (as opposed to `deleteObject`).
/// @}
/** @} */
/** @} */
 
/** @addtogroup bsl
 * @{
 */
/** @addtogroup bslma
 * @{
 */
/** @addtogroup bslma_deleterhelper
 * @{
 */
 
#include <bslscm_version.h>
 
#include <bslmf_ispolymorphic.h>
 
#include <bsls_assert.h>
#include <bsls_platform.h>
 
 
 
namespace bslma {
 
                           // ====================
                           // struct DeleterHelper
                           // ====================
 
/// This struct provides a namespace for helper functions used for deleting
/// objects in various pools and allocators.
struct DeleterHelper {
 
    // CLASS METHODS
 
    /// Destroy the specified `object` based on its dynamic type and then
    /// use the specified `allocator` to deallocate its memory footprint.
    /// Do nothing if `object` is a null pointer.  The behavior is undefined
    /// unless `allocator` is non-null, and `object`, when cast
    /// appropriately to `void *`, was allocated using `allocator` and has
    /// not already been deallocated.  Note that
    /// `dynamic_cast<void *>(object)` is applied if `TYPE` is polymorphic,
    /// and `static_cast<void *>(object)` is applied otherwise.
    template <class TYPE, class ALLOCATOR>
    static void deleteObject(const TYPE *object, ALLOCATOR *allocator);
 
    /// Destroy the specified `object` and then use the specified
    /// `allocator` to deallocate its memory footprint.  Do nothing if
    /// `object` is a null pointer.  The behavior is undefined unless
    /// `allocator` is non-null, `object` is **not** a secondary base class
    /// pointer (i.e., the address is (numerically) the same as when it was
    /// originally dispensed by `allocator`), and `object` was allocated
    /// using `allocator` and has not already been deallocated.
    template <class TYPE, class ALLOCATOR>
    static void deleteObjectRaw(const TYPE *object, ALLOCATOR *allocator);
};
 
// ============================================================================
//                          INLINE DEFINITIONS
// ============================================================================
 
             // =================================
             // local struct DeleterHelper_Helper
             // =================================
 
template <bool IS_POLYMORPHIC>
struct DeleterHelper_Helper {
    template <class TYPE>
    static void *caster(const TYPE *object)
    {
        return static_cast<void *>(const_cast<TYPE *>(object));
    }
};
 
template <>
struct DeleterHelper_Helper<true> {
    template <class TYPE>
    static void *caster(const TYPE *object)
    {
        return dynamic_cast<void *>(const_cast<TYPE *>(object));
    }
};
 
                           // --------------------
                           // struct DeleterHelper
                           // --------------------
 
// CLASS METHODS
template <class TYPE, class ALLOCATOR>
inline
void DeleterHelper::deleteObject(const TYPE *object, ALLOCATOR  *allocator)
{
    BSLS_ASSERT_SAFE(allocator);
 
    if (0 != object) {
        void *address = DeleterHelper_Helper<
                            bsl::is_polymorphic<TYPE>::value>::caster(object);
        BSLS_ASSERT_OPT(address);
 
#if defined(BSLS_PLATFORM_CMP_SUN) && BSLS_PLATFORM_CMP_VERSION < 0x5130
        const_cast<TYPE *>(object)->~TYPE();
#else
        object->~TYPE();
#endif
 
        allocator->deallocate(address);
    }
}
 
template <class TYPE, class ALLOCATOR>
inline
void DeleterHelper::deleteObjectRaw(const TYPE *object, ALLOCATOR  *allocator)
{
    BSLS_ASSERT_SAFE(allocator);
 
    if (0 != object) {
        void *address = const_cast<TYPE *>(object);
 
#if defined(BSLS_PLATFORM_CMP_SUN) && BSLS_PLATFORM_CMP_VERSION < 0x5130
        const_cast<TYPE *>(object)->~TYPE();
#else
        object->~TYPE();
#endif
 
        allocator->deallocate(address);
    }
}
 
}  // close package namespace
 
#ifndef BDE_OPENSOURCE_PUBLICATION  // BACKWARD_COMPATIBILITY
// ============================================================================
//                           BACKWARD COMPATIBILITY
// ============================================================================
 
/// This alias is defined for backward compatibility.
typedef bslma::DeleterHelper bslma_DeleterHelper;
#endif  // BDE_OPENSOURCE_PUBLICATION -- BACKWARD_COMPATIBILITY
 
 
 
#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 ----------------------------------
 
/** @} */
/** @} */
/** @} */