bslmt_semaphoreimpl_pthread.h

Go to the documentation of this file.

/// @file bslmt_semaphoreimpl_pthread.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bslmt_semaphoreimpl_pthread.h                                      -*-C++-*-
#ifndef INCLUDED_BSLMT_SEMAPHOREIMPL_PTHREAD
#define INCLUDED_BSLMT_SEMAPHOREIMPL_PTHREAD
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bslmt_semaphoreimpl_pthread bslmt_semaphoreimpl_pthread
/// @brief  Provide a POSIX implementation of `bslmt::Semaphore`.
/// @addtogroup bsl
/// @{
/// @addtogroup bslmt
/// @{
/// @addtogroup bslmt_semaphoreimpl_pthread
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bslmt_semaphoreimpl_pthread-purpose"> Purpose</a>
/// * <a href="#bslmt_semaphoreimpl_pthread-classes"> Classes </a>
/// * <a href="#bslmt_semaphoreimpl_pthread-description"> Description </a>
///   * <a href="#bslmt_semaphoreimpl_pthread-usage"> Usage </a>
///
/// # Purpose {#bslmt_semaphoreimpl_pthread-purpose}
/// Provide a POSIX implementation of `bslmt::Semaphore`.
///
/// # Classes {#bslmt_semaphoreimpl_pthread-classes}
///
/// -  bslmt::SemaphoreImpl<PosixSemaphore>: POSIX specialization
///
/// @see  bslmt_semaphore
///
/// # Description {#bslmt_semaphoreimpl_pthread-description}
/// This component provides an implementation of `bslmt::Semaphore`
/// for POSIX threads ("pthreads"), `bslmt::SemaphoreImpl<PosixSemaphore>`, via
/// the template specialization:
/// @code
/// bslmt::SemaphoreImpl<Platform::PosixThreads>
/// @endcode
/// This template class should not be used (directly) by client code.  Clients
/// should instead use `bslmt::Semaphore`.
///
/// ## Usage {#bslmt_semaphoreimpl_pthread-usage}
///
///
/// This component is an implementation detail of `bslmt` and is *not* intended
/// for direct client use.  It is subject to change without notice.  As such, a
/// usage example is not provided.
/// @}
/** @} */
/** @} */
 
/** @addtogroup bsl
 * @{
 */
/** @addtogroup bslmt
 * @{
 */
/** @addtogroup bslmt_semaphoreimpl_pthread
 * @{
 */
 
#include <bslscm_version.h>
 
#include <bslmt_platform.h>
 
#if defined(BSLMT_PLATFORM_POSIX_SEMAPHORE)
 
// Platform-specific implementation starts here.
 
#include <bsls_assert.h>
 
#include <semaphore.h>
 
 
namespace bslmt {
 
template <class SEMAPHORE_POLICY>
class SemaphoreImpl;
 
              // =============================================
              // class SemaphoreImpl<Platform::PosixSemaphore>
              // =============================================
 
/// This class provides a full specialization of `SemaphoreImpl` for
/// pthreads.  The implementation provided here defines an efficient proxy
/// for the `sem_t` pthread type, and related operations.
template <>
class SemaphoreImpl<Platform::PosixSemaphore> {
 
    // DATA
    sem_t d_sem;                // native semaphore handle
 
  private:
    // NOT IMPLEMENTED
    SemaphoreImpl(const SemaphoreImpl&);
    SemaphoreImpl& operator=(const SemaphoreImpl&);
 
  public:
    // CREATORS
 
    /// Create a semaphore initialized to the specified `count`.  This
    /// method does not return normally unless there are sufficient system
    /// resources to construct the object.
    explicit
    SemaphoreImpl(int count);
 
    /// Destroy a semaphore
    ~SemaphoreImpl();
 
    // MANIPULATORS
 
    /// Atomically increment the count of this semaphore.
    void post();
 
    /// Atomically increment the count of this semaphore by the specified `number`.  
    /// 
    /// \pre The behavior is undefined   unless `number > 0`.
    void post(int number);
 
    /// Decrement the count of this semaphore if it is positive and return
    /// 0.  Return a non-zero value otherwise.
    int tryWait();
 
    /// Block until the count of this semaphore is a positive value and
    /// atomically decrement it.
    void wait();
 
    // ACCESSORS
 
    /// Return the current value of this semaphore.
    int getValue() const;
};
 
// ============================================================================
//                             INLINE DEFINITIONS
// ============================================================================
 
              // ---------------------------------------------
              // class SemaphoreImpl<Platform::PosixSemaphore>
              // ---------------------------------------------
 
// CREATORS
inline
SemaphoreImpl<bslmt::Platform::PosixSemaphore>::~SemaphoreImpl()
{
    int result = ::sem_destroy(&d_sem);
 
    (void) result;
    BSLS_ASSERT(result == 0);
}
 
// MANIPULATORS
inline
void SemaphoreImpl<bslmt::Platform::PosixSemaphore>::post()
{
    int result = ::sem_post(&d_sem);
 
    (void) result;
    BSLS_ASSERT(result == 0);
}
 
inline
int SemaphoreImpl<bslmt::Platform::PosixSemaphore>::tryWait()
{
    return ::sem_trywait(&d_sem);
}
 
// ACCESSORS
inline
int SemaphoreImpl<bslmt::Platform::PosixSemaphore>::getValue() const
{
    int value = 0;
    int result = ::sem_getvalue(const_cast<sem_t *>(&d_sem), &value);
 
    (void) result;
    BSLS_ASSERT_SAFE(result == 0);
 
    return value;
}
 
}  // close package namespace
 
 
#endif  // defined(BSLMT_PLATFORM_POSIX_SEMAPHORE)
 
#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 ----------------------------------
 
/** @} */
/** @} */
/** @} */