SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
- OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
#ifndef CDSLIB_GC_IMPL_HP_DECL_H
*/
typedef hp::ThreadGC thread_gc_impl;
+ /// Exception "Too many Hazard Pointer"
+ typedef hp::GarbageCollector::too_many_hazard_ptr too_many_hazard_ptr_exception;
+
/// Wrapper for hp::ThreadGC class
/**
@headerfile cds/gc/hp.h
public: // for internal use only!!!
//@cond
- static cds::gc::hp::details::hp_guard& alloc_guard(); // inline in hp_impl.h
- static void free_guard( cds::gc::hp::details::hp_guard& g ); // inline in hp_impl.h
+ static cds::gc::hp::details::hp_guard* alloc_guard(); // inline in hp_impl.h
+ static void free_guard( cds::gc::hp::details::hp_guard* g ); // inline in hp_impl.h
//@endcond
};
/**
@headerfile cds/gc/hp.h
- A guard is the hazard pointer.
- Additionally, the \p %Guard class manages allocation and deallocation of the hazard pointer
+ A guard is a hazard pointer.
+ Additionally, the \p %Guard class manages allocation and deallocation of the hazard pointer.
+
+ \p %Guard object is movable but not copyable.
+
+ The guard object can be in two states:
+ - unlinked - the guard is not linked with any internal hazard pointer.
+ In this state no operation except \p link() and move assignment is supported.
+ - linked (default) - the guard allocates an internal hazard pointer and fully operable.
+
+ Due to performance reason the implementation does not check state of the guard in runtime.
- A \p %Guard object is not copy- and move-constructible
- and not copy- and move-assignable.
+ @warning Move assignment can transfer the guard in unlinked state, use with care.
*/
- class Guard : public hp::guard
+ class Guard
{
- //@cond
- typedef hp::guard base_class;
- //@endcond
-
public:
- /// Default ctor
- Guard()
+ /// Default ctor allocates a guard (hazard pointer) from thread-private storage
+ /**
+ @warning Can throw \p too_many_hazard_ptr_exception if internal hazard pointer objects are exhausted.
+ */
+ Guard(); // inline in hp_impl.h
+
+ /// Initilalizes an unlinked guard i.e. the guard contains no hazard pointer. Used for move semantics support
+ explicit Guard( std::nullptr_t ) CDS_NOEXCEPT
+ : m_guard( nullptr )
{}
- //@cond
+ /// Move ctor - \p src guard becomes unlinked (transfer internal guard ownership)
+ Guard( Guard&& src ) CDS_NOEXCEPT
+ : m_guard( src.m_guard )
+ {
+ src.m_guard = nullptr;
+ }
+
+ /// Move assignment: the internal guards are swapped between \p src and \p this
+ /**
+ @warning \p src will become in unlinked state if \p this was unlinked on entry.
+ */
+ Guard& operator=( Guard&& src ) CDS_NOEXCEPT
+ {
+ std::swap( m_guard, src.m_guard );
+ return *this;
+ }
+
+ /// Copy ctor is prohibited - the guard is not copyable
Guard( Guard const& ) = delete;
- Guard( Guard&& s ) = delete;
- Guard& operator=(Guard const&) = delete;
- Guard& operator=(Guard&&) = delete;
- //@endcond
+
+ /// Copy assignment is prohibited
+ Guard& operator=( Guard const& ) = delete;
+
+ /// Frees the internal hazard pointer if the guard is in linked state
+ ~Guard()
+ {
+ unlink();
+ }
+
+ /// Checks if the guard object linked with any internal hazard pointer
+ bool is_linked() const
+ {
+ return m_guard != nullptr;
+ }
+
+ /// Links the guard with internal hazard pointer if the guard is in unlinked state
+ /**
+ @warning Can throw \p too_many_hazard_ptr_exception if internal hazard pointer objects are exhausted.
+ */
+ void link(); // inline in hp_impl.h
+
+ /// Unlinks the guard from internal hazard pointer; the guard becomes in unlinked state
+ void unlink(); // inline in hp_impl.h
/// Protects a pointer of type \p atomic<T*>
/**
The function tries to load \p toGuard and to store it
to the HP slot repeatedly until the guard's value equals \p toGuard
+
+ @warning The guad object should be in linked state, otherwise the result is undefined
*/
template <typename T>
T protect( atomics::atomic<T> const& toGuard )
{
+ assert( m_guard != nullptr );
+
T pCur = toGuard.load(atomics::memory_order_acquire);
T pRet;
do {
value_type * operator()( T * p );
};
\endcode
- Really, the result of <tt> f( toGuard.load() ) </tt> is assigned to the hazard pointer.
+ Actually, the result of <tt> f( toGuard.load() ) </tt> is assigned to the hazard pointer.
+
+ @warning The guad object should be in linked state, otherwise the result is undefined
*/
template <typename T, class Func>
T protect( atomics::atomic<T> const& toGuard, Func f )
{
+ assert( m_guard != nullptr );
+
T pCur = toGuard.load(atomics::memory_order_acquire);
T pRet;
do {
/**
The function equals to a simple assignment the value \p p to guard, no loop is performed.
Can be used for a pointer that cannot be changed concurrently
+
+ @warning The guad object should be in linked state, otherwise the result is undefined
*/
template <typename T>
- T * assign( T * p ); // inline in hp_impl.h
+ T * assign( T* p ); // inline in hp_impl.h
//@cond
std::nullptr_t assign( std::nullptr_t )
{
- return base_class::operator =(nullptr);
+ assert(m_guard != nullptr );
+ return *m_guard = nullptr;
}
//@endcond
- /// Copy from \p src guard to \p this guard
+ /// Copy a value guarded from \p src guard to \p this guard (valid only in linked state)
void copy( Guard const& src )
{
assign( src.get_native() );
/**
The function equals to a simple assignment of <tt>p.ptr()</tt>, no loop is performed.
Can be used for a marked pointer that cannot be changed concurrently.
+
+ @warning The guad object should be in linked state, otherwise the result is undefined
*/
template <typename T, int BITMASK>
T * assign( cds::details::marked_ptr<T, BITMASK> p )
{
- return base_class::operator =( p.ptr() );
+ return assign( p.ptr());
}
- /// Clear value of the guard
+ /// Clear value of the guard (valid only in linked state)
void clear()
{
assign( nullptr );
}
- /// Get the value currently protected
+ /// Get the value currently protected (valid only in linked state)
template <typename T>
T * get() const
{
return reinterpret_cast<T *>( get_native() );
}
- /// Get native hazard pointer stored
+ /// Get native hazard pointer stored (valid only in linked state)
guarded_pointer get_native() const
{
- return base_class::get();
+ assert( m_guard != nullptr );
+ return m_guard->get();
}
+
+ //@cond
+ hp::details::hp_guard* release()
+ {
+ hp::details::hp_guard* g = m_guard;
+ m_guard = nullptr;
+ return g;
+ }
+ //@endcond
+
+ private:
+ //@cond
+ hp::details::hp_guard* m_guard;
+ //@endcond
};
/// Array of Hazard Pointer guards
The class is intended for allocating an array of hazard pointer guards.
Template parameter \p Count defines the size of the array.
- A \p %GuardArray object is not copy- and move-constructible
- and not copy- and move-assignable.
*/
template <size_t Count>
- class GuardArray : public hp::array<Count>
+ class GuardArray
{
- //@cond
- typedef hp::array<Count> base_class;
- //@endcond
public:
/// Rebind array for other size \p Count2
template <size_t Count2>
struct rebind {
- typedef GuardArray<Count2> other ; ///< rebinding result
+ typedef GuardArray<Count2> other; ///< rebinding result
};
+ /// Array capacity
+ static CDS_CONSTEXPR const size_t c_nCapacity = Count;
+
public:
- /// Default ctor
- GuardArray()
- {}
+ /// Default ctor allocates \p Count hazard pointers
+ GuardArray(); // inline in hp_impl.h
- //@cond
- GuardArray( GuardArray const& ) = delete;
+ /// Move ctor is prohibited
GuardArray( GuardArray&& ) = delete;
- GuardArray& operator=(GuardArray const&) = delete;
- GuardArray& operator=(GuardArray&&) = delete;
- //@endcond
+
+ /// Move assignment is prohibited
+ GuardArray& operator=( GuardArray&& ) = delete;
+
+ /// Copy ctor is prohibited
+ GuardArray( GuardArray const& ) = delete;
+
+ /// Copy assignment is prohibited
+ GuardArray& operator=( GuardArray const& ) = delete;
+
+ /// Frees allocated hazard pointers
+ ~GuardArray(); // inline in hp_impl.h
/// Protects a pointer of type \p atomic<T*>
/**
template <typename T>
T protect( size_t nIndex, atomics::atomic<T> const& toGuard )
{
+ assert( nIndex < capacity());
+
T pRet;
do {
pRet = assign( nIndex, toGuard.load(atomics::memory_order_acquire) );
template <typename T, class Func>
T protect( size_t nIndex, atomics::atomic<T> const& toGuard, Func f )
{
+ assert( nIndex < capacity() );
+
T pRet;
do {
assign( nIndex, f( pRet = toGuard.load(atomics::memory_order_acquire) ));
/// Clear value of the slot \p nIndex
void clear( size_t nIndex )
{
- base_class::clear( nIndex );
+ m_arr.clear( nIndex );
}
/// Get current value of slot \p nIndex
/// Get native hazard pointer stored
guarded_pointer get_native( size_t nIndex ) const
{
- return base_class::operator[](nIndex).get();
+ assert( nIndex < capacity() );
+ return m_arr[nIndex]->get();
}
+ //@cond
+ hp::details::hp_guard* release( size_t nIndex ) CDS_NOEXCEPT
+ {
+ return m_arr.release( nIndex );
+ }
+ //@endcond
+
/// Capacity of the guard array
static CDS_CONSTEXPR size_t capacity()
{
- return Count;
+ return c_nCapacity;
}
+
+ private:
+ //@cond
+ hp::details::hp_array<Count> m_arr;
+ //@endcond
};
/// Guarded pointer
return p;
}
};
+
+ template <typename GT, typename VT, typename C> friend class guarded_ptr;
//@endcond
public:
/// Functor for casting \p guarded_type to \p value_type
typedef typename std::conditional< std::is_same<Cast, void>::value, trivial_cast, Cast >::type value_cast;
- //@cond
- typedef cds::gc::hp::details::hp_guard native_guard;
- //@endcond
-
- private:
- //@cond
- native_guard * m_pGuard;
- //@endcond
-
public:
/// Creates empty guarded pointer
guarded_ptr() CDS_NOEXCEPT
: m_pGuard(nullptr)
- {
- alloc_guard();
- }
+ {}
//@cond
+ explicit guarded_ptr( hp::details::hp_guard* g ) CDS_NOEXCEPT
+ : m_pGuard( g )
+ {}
+
/// Initializes guarded pointer with \p p
- explicit guarded_ptr( guarded_type * p ) CDS_NOEXCEPT
+ explicit guarded_ptr( guarded_type* p ) CDS_NOEXCEPT
: m_pGuard( nullptr )
{
reset(p);
gp.m_pGuard = nullptr;
}
+ /// Move ctor
+ template <typename GT, typename VT, typename C>
+ guarded_ptr( guarded_ptr<GT, VT, C>&& gp ) CDS_NOEXCEPT
+ : m_pGuard( gp.m_pGuard )
+ {
+ gp.m_pGuard = nullptr;
+ }
+
+ /// Ctor from \p Guard
+ explicit guarded_ptr( Guard&& g ) CDS_NOEXCEPT
+ : m_pGuard( g.release() )
+ {}
+
/// The guarded pointer is not copy-constructible
guarded_ptr( guarded_ptr const& gp ) = delete;
/// Clears the guarded pointer
/**
- \ref release is called if guarded pointer is not \ref empty
+ \ref release() is called if guarded pointer is not \ref empty()
*/
~guarded_ptr() CDS_NOEXCEPT
{
- free_guard();
+ release();
}
/// Move-assignment operator
guarded_ptr& operator=( guarded_ptr&& gp ) CDS_NOEXCEPT
{
- // Hazard Pointer array is organized as a stack
- if ( m_pGuard && m_pGuard > gp.m_pGuard ) {
- m_pGuard->set( gp.m_pGuard->get(atomics::memory_order_relaxed) );
- gp.free_guard();
- }
- else {
- free_guard();
- m_pGuard = gp.m_pGuard;
- gp.m_pGuard = nullptr;
- }
+ std::swap( m_pGuard, gp.m_pGuard );
+ return *this;
+ }
+
+ /// Move-assignment from \p Guard
+ guarded_ptr& operator=( Guard&& g ) CDS_NOEXCEPT
+ {
+ std::swap( m_pGuard, g.m_guard );
return *this;
}
//@cond
// For internal use only!!!
- native_guard& guard() CDS_NOEXCEPT
- {
- alloc_guard();
- assert( m_pGuard );
- return *m_pGuard;
- }
-
void reset(guarded_type * p) CDS_NOEXCEPT
{
alloc_guard();
void alloc_guard()
{
if ( !m_pGuard )
- m_pGuard = &thread_gc::alloc_guard();
+ m_pGuard = thread_gc::alloc_guard();
}
void free_guard()
{
if ( m_pGuard ) {
- thread_gc::free_guard( *m_pGuard );
+ thread_gc::free_guard( m_pGuard );
m_pGuard = nullptr;
}
}
//@endcond
+
+ private:
+ //@cond
+ hp::details::hp_guard* m_pGuard;
+ //@endcond
};
public:
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