bdlbb_pooledblobbufferfactory.h

Go to the documentation of this file.

/// @file bdlbb_pooledblobbufferfactory.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bdlbb_pooledblobbufferfactory.h                                    -*-C++-*-
#ifndef INCLUDED_BDLBB_POOLEDBLOBBUFFERFACTORY
#define INCLUDED_BDLBB_POOLEDBLOBBUFFERFACTORY
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bdlbb_pooledblobbufferfactory bdlbb_pooledblobbufferfactory
/// @brief  Provide a concrete implementation of `bdlbb::BlobBufferFactory`.
/// @addtogroup bdl
/// @{
/// @addtogroup bdlbb
/// @{
/// @addtogroup bdlbb_pooledblobbufferfactory
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bdlbb_pooledblobbufferfactory-purpose"> Purpose</a>
/// * <a href="#bdlbb_pooledblobbufferfactory-classes"> Classes </a>
/// * <a href="#bdlbb_pooledblobbufferfactory-description"> Description </a>
///   * <a href="#bdlbb_pooledblobbufferfactory-thread-safety"> Thread Safety </a>
///   * <a href="#bdlbb_pooledblobbufferfactory-potential-lifetime-issues"> Potential Lifetime Issues </a>
///
/// # Purpose {#bdlbb_pooledblobbufferfactory-purpose}
/// Provide a concrete implementation of `bdlbb::BlobBufferFactory`.
///
/// # Classes {#bdlbb_pooledblobbufferfactory-classes}
///
/// -  bdlbb::PooledBlobBufferFactory: mechanism pooling `bdlbb::BlobBuffer`s
///
/// @see  bdlbb_blob, bdlma_concurrentpool
///
/// # Description {#bdlbb_pooledblobbufferfactory-description}
/// This component provides a mechanism for allocating
/// `bdlbb::BlobBuffer` objects of a fixed specified size.  The size is passed
/// at construction of the `bdlbb::PooledBlobBufferFactory` instance.  A
/// `bdlbb::BlobBuffer` is basically a shared pointer to a buffer of `char` of
/// the prescribed size.  Thus it is generally more efficient to create them
/// with a uniform size, for the same reason as a pool is more efficient than a
/// general-purpose memory allocator.  In order to gain further efficiency, this
/// factory allocates the shared pointer representation together with the buffer
/// (contiguously).
///
/// ## Thread Safety {#bdlbb_pooledblobbufferfactory-thread-safety}
///
///
/// The `bdlbb::PooledBlobBufferFactory` class is *fully thread-safe* (i.e., all
/// non-creator methods can correctly execute concurrently).  See
/// @ref bsldoc_glossary  for complete definitions of *fully thread-safe*.
///
/// It is safe to access and modify factory from multiple threads.  However, it
/// is *not* safe to allocate and load a new buffer into the same `BlobBuffer`
/// object simultaneously from multiple threads.
///
/// ## Potential Lifetime Issues {#bdlbb_pooledblobbufferfactory-potential-lifetime-issues}
///
///
/// Be aware that the destruction of a `bdlbb::PooledBlobBufferFactory` object
/// releases all the `BlobBuffer` objects allocated by that factory. A common
/// misconception is that, because of the use of `shared_ptr`, the data referred
/// to in `BlobBuffer` objects created will remain valid until the last shared
/// reference is destroyed, even if a reference outlives the
/// `PooledBlobBufferFactory` that created it. This is *not* the case.
/// Destroying a `PooledBlobBufferFactory` releases any memory created by that
/// pool, even if shared references remain to the data, and it is therefore
/// undefined behavior to use any `BlobBuffer` created by a pool after that pool
/// is destroyed. A user must clearly understand the lifetime of memory
/// allocated by a subsystem, and scope the lifetime of the
/// `PooledBlobBufferFactory` to be greater than the active lifetime of that
/// subsystem.
/// @}
/** @} */
/** @} */
 
/** @addtogroup bdl
 * @{
 */
/** @addtogroup bdlbb
 * @{
 */
/** @addtogroup bdlbb_pooledblobbufferfactory
 * @{
 */
 
#include <bdlscm_version.h>
 
#include <bdlbb_blob.h>
 
#include <bdlma_concurrentpoolallocator.h>
 
#include <bsls_keyword.h>
 
 
namespace bdlbb {
 
                       // =============================
                       // class PooledBlobBufferFactory
                       // =============================
 
/// This class implements the `BlobBufferFactory` protocol and provides a
/// mechanism for allocating `BlobBuffer` objects of a fixed size passed at
/// construction.
///
/// See @ref bdlbb_pooledblobbufferfactory 
class PooledBlobBufferFactory : public BlobBufferFactory {
 
    // DATA
    int d_bufferSize;                         // size of allocated blob buffers
 
    bdlma::ConcurrentPoolAllocator d_spPool;  // pool used to allocate shared
                                              // pointers and buffers
                                              // contiguously
  public:
    // CREATORS
 
    PooledBlobBufferFactory(int               bufferSize,
                            bslma::Allocator *basicAllocator = 0);
    PooledBlobBufferFactory(int                          bufferSize,
                            bsls::BlockGrowth::Strategy  growthStrategy,
                            bslma::Allocator            *basicAllocator = 0);
    /// Create a pooled factory for allocating `BlobBuffer` objects of the
    /// specified `bufferSize`.  Optionally specify a `growthStrategy` used
    /// to control the growth of internal memory chunks (from which memory
    /// blocks are dispensed).  If `growthStrategy` is not specified,
    /// geometric growth is used.  If `growthStrategy` is specified,
    /// optionally specify a `maxBlocksPerChunk`, indicating the maximum
    /// number of blocks to be allocated at once when the underlying pool
    /// must be replenished.  If `maxBlocksPerChunk` is not specified, an
    /// implementation-defined value is used.  If geometric growth is used,
    /// the chunk size grows starting at the value returned by `blockSize`,
    /// doubling in size until the size is exactly
    /// `blockSize() * maxBlocksPerChunk`.  If constant growth is used, the
    /// chunk size is always `maxBlocksPerChunk`.  Optionally specify a
    /// `basicAllocator` used to supply memory.  If `basicAllocator` is 0,
    /// the currently installed default allocator is used.  The behavior is
    /// undefined unless `0 < bufferSize`, and `1 <= maxBlocksPerChunk`.
    PooledBlobBufferFactory(int                          bufferSize,
                            bsls::BlockGrowth::Strategy  growthStrategy,
                            int                          maxBlocksPerChunk,
                            bslma::Allocator            *basicAllocator = 0);
 
    /// Destroy this factory.  This operation releases all `BlobBuffer`
    /// objects allocated via this factory.
    ~PooledBlobBufferFactory() BSLS_KEYWORD_OVERRIDE;
 
    // MANIPULATORS
 
    /// Allocate a new buffer with the buffer size specified at construction
    /// and load it into the specified `buffer`.  Note that destruction of
    /// the `bdlbb::PooledBlobBufferFactory` object releases all
    /// `BlobBuffer` objects allocated via this factory.
    void allocate(BlobBuffer *buffer) BSLS_KEYWORD_OVERRIDE;
 
    // ACCESSORS
 
    /// Return the buffer size specified at construction of this factory.
    int bufferSize() const;
};
 
// ============================================================================
//                             INLINE DEFINITIONS
// ============================================================================
 
                       // -----------------------------
                       // class PooledBlobBufferFactory
                       // -----------------------------
 
// ACCESSORS
inline
int PooledBlobBufferFactory::bufferSize() const
{
    return d_bufferSize;
}
 
}  // close package namespace
 
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2018 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */