bslmt_conditionimpl_pthread.h

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/// @file bslmt_conditionimpl_pthread.h
///
/// The content of this file has been pre-processed for Doxygen.
///
 
 
// bslmt_conditionimpl_pthread.h                                      -*-C++-*-
#ifndef INCLUDED_BSLMT_CONDITIONIMPL_PTHREAD
#define INCLUDED_BSLMT_CONDITIONIMPL_PTHREAD
 
#include <bsls_ident.h>
BSLS_IDENT("$Id: $")
 
/// @defgroup bslmt_conditionimpl_pthread bslmt_conditionimpl_pthread
/// @brief  Provide a POSIX implementation of `bslmt::Condition`.
/// @addtogroup bsl
/// @{
/// @addtogroup bslmt
/// @{
/// @addtogroup bslmt_conditionimpl_pthread
/// @{
///
/// <h1> Outline </h1>
/// * <a href="#bslmt_conditionimpl_pthread-purpose"> Purpose</a>
/// * <a href="#bslmt_conditionimpl_pthread-classes"> Classes </a>
/// * <a href="#bslmt_conditionimpl_pthread-description"> Description </a>
///   * <a href="#bslmt_conditionimpl_pthread-supported-clock-types"> Supported Clock-Types </a>
///   * <a href="#bslmt_conditionimpl_pthread-usage"> Usage </a>
///
/// # Purpose {#bslmt_conditionimpl_pthread-purpose}
/// Provide a POSIX implementation of `bslmt::Condition`.
///
/// # Classes {#bslmt_conditionimpl_pthread-classes}
///
/// -  bslmt::ConditionImpl<PosixThreads>: POSIX specialization
///
/// @see  bslmt_condition
///
/// # Description {#bslmt_conditionimpl_pthread-description}
/// This component provides an implementation of `bslmt::Condition`
/// for POSIX threads ("pthreads"), `bslmt::ConditionImpl<PosixThreads>`, via
/// the template specialization:
/// @code
/// bslmt::ConditionImpl<Platform::PosixThreads>
/// @endcode
/// This template class should not be used (directly) by client code.  Clients
/// should instead use `bslmt::Condition`.
///
/// ## Supported Clock-Types {#bslmt_conditionimpl_pthread-supported-clock-types}
///
///
/// `bsls::SystemClockType` supplies the enumeration indicating the system clock
/// on which timeouts supplied to other methods should be based.  If the clock
/// type indicated at construction is `bsls::SystemClockType::e_REALTIME`, the
/// `absTime` argument passed to the `timedWait` method should be expressed as
/// an *absolute* offset since 00:00:00 UTC, January 1, 1970 (which matches the
/// epoch used in `bsls::SystemTime::now(bsls::SystemClockType::e_REALTIME)`.
/// If the clock type indicated at construction is
/// `bsls::SystemClockType::e_MONOTONIC`, the `absTime` argument passed to the
/// `timedWait` method should be expressed as an *absolute* offset since the
/// epoch of this clock (which matches the epoch used in
/// `bsls::SystemTime::now(bsls::SystemClockType::e_MONOTONIC)`.
///
/// ## Usage {#bslmt_conditionimpl_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_conditionimpl_pthread
 * @{
 */
 
#include <bslscm_version.h>
 
#include <bslmt_mutex.h>
#include <bslmt_platform.h>
 
#include <bsls_platform.h>
#include <bsls_systemclocktype.h>
#include <bsls_timeinterval.h>
 
#ifdef BSLMT_PLATFORM_POSIX_THREADS
 
// Platform-specific implementation starts here.
 
#include <bsl_ctime.h>
#include <bsl_c_errno.h>
 
#include <pthread.h>
 
 
namespace bslmt {
 
template <class THREAD_POLICY>
class ConditionImpl;
 
               // ===========================================
               // class ConditionImpl<Platform::PosixThreads>
               // ===========================================
 
/// This class provides a full specialization of `Condition` for pthreads.
/// The implementation provided here defines an efficient proxy for the
/// @ref pthread_cond_t  pthread type, and related operations.
template <>
class ConditionImpl<Platform::PosixThreads> {
 
    // DATA
    pthread_cond_t              d_cond;       // provides post/wait for
                                              // condition
 
    bsls::SystemClockType::Enum d_clockType;  // clock type used in 'timedWait'
 
  private:
    // NOT IMPLEMENTED
    ConditionImpl(const ConditionImpl&);
    ConditionImpl& operator=(const ConditionImpl&);
 
  public:
    // TYPES
 
    /// The value `timedWait` returns when a timeout occurs.
    enum { e_TIMED_OUT = -1 };
 
    // CREATORS
 
    /// Create a condition variable object.  Optionally specify a
    /// `clockType` indicating the type of the system clock against which
    /// the `bsls::TimeInterval` `absTime` timeouts passed to the
    /// `timedWait` method are to be interpreted (see {Supported
    /// Clock-Types} in the component-level documentation).  If `clockType`
    /// is not specified then the realtime system clock is used.  This
    /// method does not return normally unless there are sufficient system
    /// resources to construct the object.
    explicit
    ConditionImpl(bsls::SystemClockType::Enum clockType
                                          = bsls::SystemClockType::e_REALTIME);
 
    /// Destroy condition variable this object.
    ~ConditionImpl();
 
    // MANIPULATORS
 
    /// Signal this condition object; wake up all threads that are currently
    /// waiting on this condition.
    void broadcast();
 
    /// Signal this condition object; wake up a single thread that is
    /// currently waiting on this condition.
    void signal();
 
    /// Atomically unlock the specified `mutex` and suspend execution of the
    /// current thread until this condition object is "signaled" (i.e., one
    /// of the `signal` or `broadcast` methods is invoked on this object) or
    /// until the specified `absTime` timeout expires, then re-acquire a
    /// lock on the `mutex`.  `absTime` is an *absolute* time represented as
    /// an interval from some epoch, which is determined by the clock
    /// indicated at construction (see {Supported Clock-Types} in the
    /// component-level documentation), and is the earliest time at which
    /// the timeout may occur.  The `mutex` remains locked by the calling
    /// thread upon returning from this function.  Return 0 on success,
    /// `e_TIMED_OUT` on timeout, and a non-zero value different from `e_TIMED_OUT` if an error occurs.  
    /// 
    /// \pre The behavior is undefined   unless
    /// `mutex` is locked by the calling thread prior to calling this method.  
    /// 
    /// \note Note that   spurious wakeups are rare but possible, i.e.,
    /// this method may succeed (return 0) and return control to the thread
    /// without the condition object being signaled.  Also note that the
    /// actual time of the timeout depends on many factors including system
    /// scheduling and system timer resolution, and may be significantly
    /// later than the time requested.
    int timedWait(Mutex *mutex, const bsls::TimeInterval& absTime);
 
    /// Atomically unlock the specified `mutex` and suspend execution of the
    /// current thread until this condition object is "signaled" (i.e.,
    /// either `signal` or `broadcast` is invoked on this object in another
    /// thread), then re-acquire a lock on the `mutex`.  Return 0 on
    /// success, and a non-zero value otherwise.  Spurious wakeups are rare
    /// but possible; i.e., this method may succeed (return 0), and return
    /// control to the thread without the condition object being signaled. 
    /// 
    /// \pre The behavior is undefined   unless `mutex` is locked by the calling thread prior to calling this method.  
    /// 
    /// \note Note that   `mutex` remains
    /// locked by the calling thread upon return from this function.
    int wait(Mutex *mutex);
 
    // ACCESSORS
 
    /// Return the clock type used for timeouts.
    bsls::SystemClockType::Enum clockType() const;
};
 
// ============================================================================
//                             INLINE DEFINITIONS
// ============================================================================
 
               // -------------------------------------------
               // class ConditionImpl<Platform::PosixThreads>
               // -------------------------------------------
 
// CREATORS
inline
ConditionImpl<bslmt::Platform::PosixThreads>::~ConditionImpl()
{
    pthread_cond_destroy(&d_cond);
}
 
// MANIPULATORS
inline
void ConditionImpl<bslmt::Platform::PosixThreads>::broadcast()
{
    pthread_cond_broadcast(&d_cond);
}
 
inline
void ConditionImpl<bslmt::Platform::PosixThreads>::signal()
{
    pthread_cond_signal(&d_cond);
}
 
inline
int ConditionImpl<bslmt::Platform::PosixThreads>::wait(Mutex *mutex)
{
    return pthread_cond_wait(&d_cond, &mutex->nativeMutex());
}
 
// ACCESSORS
inline
bsls::SystemClockType::Enum
ConditionImpl<bslmt::Platform::PosixThreads>::clockType() const
{
    return d_clockType;
}
 
}  // close package namespace
 
 
#endif  // BSLMT_PLATFORM_POSIX_THREADS
 
#endif
 
// ----------------------------------------------------------------------------
// Copyright 2023 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 ----------------------------------
 
/** @} */
/** @} */
/** @} */