--- /dev/null
+/*
+ This file is a part of libcds - Concurrent Data Structures library
+
+ (C) Copyright Maxim Khizhinsky (libcds.dev@gmail.com) 2006-2017
+
+ Source code repo: http://github.com/khizmax/libcds/
+ Download: http://sourceforge.net/projects/libcds/files/
+
+ Redistribution and use in source and binary forms, with or without
+ modification, are permitted provided that the following conditions are met:
+
+ * Redistributions of source code must retain the above copyright notice, this
+ list of conditions and the following disclaimer.
+
+ * Redistributions in binary form must reproduce the above copyright notice,
+ this list of conditions and the following disclaimer in the documentation
+ and/or other materials provided with the distribution.
+
+ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+ AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
+ DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE
+ FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
+ 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.
+*/
+
+#ifndef CDSLIB_INTRUSIVE_DETAILS_SKIP_LIST_BASE_H
+#define CDSLIB_INTRUSIVE_DETAILS_SKIP_LIST_BASE_H
+
+#include <cds/intrusive/details/base.h>
+#include <cds/details/marked_ptr.h>
+#include <cds/algo/bitop.h>
+#include <cds/os/timer.h>
+#include <cds/urcu/options.h>
+
+namespace cds { namespace intrusive {
+ /// SkipListSet related definitions
+ /** @ingroup cds_intrusive_helper
+ */
+ namespace skip_list {
+ /// The maximum possible height of any skip-list
+ static unsigned int const c_nHeightLimit = 32;
+
+ /// Skip list node
+ /**
+ Template parameters:
+ - \p GC - garbage collector
+ - \p Tag - a \ref cds_intrusive_hook_tag "tag"
+ */
+ template <class GC, typename Tag = opt::none>
+ class node
+ {
+ public:
+ typedef GC gc; ///< Garbage collector
+ typedef Tag tag; ///< tag
+
+ typedef cds::details::marked_ptr<node, 1> marked_ptr; ///< marked pointer
+ typedef typename gc::template atomic_marked_ptr< marked_ptr> atomic_marked_ptr; ///< atomic marked pointer specific for GC
+ //@cond
+ typedef atomic_marked_ptr tower_item_type;
+
+ //@endcond
+
+ protected:
+ //@cond
+ atomic_marked_ptr m_pNext; ///< Next item in bottom-list (list at level 0)
+ unsigned int m_nHeight; ///< Node height (size of \p m_arrNext array). For node at level 0 the height is 1.
+ atomic_marked_ptr * m_arrNext; ///< Array of next items for levels 1 .. m_nHeight - 1. For node at level 0 \p m_arrNext is \p nullptr
+ atomics::atomic<unsigned int> m_nUnlink; ///< Unlink helper
+ //@endcond
+
+ public:
+ node()
+ : m_pNext( nullptr )
+ , m_nHeight( 1 )
+ , m_arrNext( nullptr )
+ {
+ m_nUnlink.store( 1, atomics::memory_order_release );
+ }
+
+
+ /// Constructs a node's tower of height \p nHeight
+ void make_tower( unsigned int nHeight, atomic_marked_ptr * nextTower )
+ {
+ assert( nHeight > 0 );
+ assert( (nHeight == 1 && nextTower == nullptr) // bottom-list node
+ || (nHeight > 1 && nextTower != nullptr) // node at level of more than 0
+ );
+
+ m_arrNext = nextTower;
+ m_nHeight = nHeight;
+ m_nUnlink.store( nHeight, atomics::memory_order_release );
+ }
+
+ //@cond
+ atomic_marked_ptr * release_tower()
+ {
+ atomic_marked_ptr * pTower = m_arrNext;
+ m_arrNext = nullptr;
+ m_nHeight = 1;
+ return pTower;
+ }
+
+ atomic_marked_ptr * get_tower() const
+ {
+ return m_arrNext;
+ }
+
+ bool has_tower() const
+ {
+ return m_nHeight > 1;
+ }
+ //@endcond
+
+ /// Access to element of next pointer array
+ atomic_marked_ptr& next( unsigned int nLevel )
+ {
+ assert( nLevel < height());
+ assert( nLevel == 0 || (nLevel > 0 && m_arrNext != nullptr));
+
+ if ( nLevel ) {
+ // TSan: data race between m_arrNext[ nLevel - 1 ] and make_tower()
+ // In fact, m_arrNext is a const array that is never changed
+ CDS_TSAN_ANNOTATE_HAPPENS_BEFORE( &m_arrNext[ nLevel - 1 ] );
+ return m_arrNext[nLevel - 1];
+ }
+ return m_pNext;
+ }
+
+ /// Access to element of next pointer array (const version)
+ atomic_marked_ptr const& next( unsigned int nLevel ) const
+ {
+ assert( nLevel < height());
+ assert( nLevel == 0 || nLevel > 0 && m_arrNext != nullptr );
+
+ if ( nLevel ) {
+ CDS_TSAN_ANNOTATE_HAPPENS_BEFORE( &m_arrNext[nLevel - 1] );
+ return m_arrNext[nLevel - 1];
+ }
+ return m_pNext;
+ }
+
+ /// Access to element of next pointer array (synonym for \p next() function)
+ atomic_marked_ptr& operator[]( unsigned int nLevel )
+ {
+ return next( nLevel );
+ }
+
+ /// Access to element of next pointer array (synonym for \p next() function)
+ atomic_marked_ptr const& operator[]( unsigned int nLevel ) const
+ {
+ return next( nLevel );
+ }
+
+ /// Height of the node
+ unsigned int height() const
+ {
+ return m_nHeight;
+ }
+
+ /// Clears internal links
+ void clear()
+ {
+ assert( m_arrNext == nullptr );
+ m_pNext.store( marked_ptr(), atomics::memory_order_release );
+ }
+
+ //@cond
+ bool is_cleared() const
+ {
+ return m_pNext == atomic_marked_ptr()
+ && m_arrNext == nullptr
+ && m_nHeight <= 1;
+ }
+
+ bool level_unlinked( unsigned nCount = 1 )
+ {
+ return m_nUnlink.fetch_sub( nCount, atomics::memory_order_relaxed ) == 1;
+ }
+
+ bool is_upper_level( unsigned nLevel ) const
+ {
+ return m_nUnlink.load( atomics::memory_order_relaxed ) == nLevel + 1;
+ }
+ //@endcond
+ };
+
+ //@cond
+ struct undefined_gc;
+ struct default_hook {
+ typedef undefined_gc gc;
+ typedef opt::none tag;
+ };
+ //@endcond
+
+ //@cond
+ template < typename HookType, typename... Options>
+ struct hook
+ {
+ typedef typename opt::make_options< default_hook, Options...>::type options;
+ typedef typename options::gc gc;
+ typedef typename options::tag tag;
+ typedef node<gc, tag> node_type;
+ typedef HookType hook_type;
+ };
+ //@endcond
+
+ /// Base hook
+ /**
+ \p Options are:
+ - \p opt::gc - garbage collector
+ - \p opt::tag - a \ref cds_intrusive_hook_tag "tag"
+ */
+ template < typename... Options >
+ struct base_hook: public hook< opt::base_hook_tag, Options... >
+ {};
+
+ /// Member hook
+ /**
+ \p MemberOffset defines offset in bytes of \ref node member into your structure.
+ Use \p offsetof macro to define \p MemberOffset
+
+ \p Options are:
+ - \p opt::gc - garbage collector
+ - \p opt::tag - a \ref cds_intrusive_hook_tag "tag"
+ */
+ template < size_t MemberOffset, typename... Options >
+ struct member_hook: public hook< opt::member_hook_tag, Options... >
+ {
+ //@cond
+ static const size_t c_nMemberOffset = MemberOffset;
+ //@endcond
+ };
+
+ /// Traits hook
+ /**
+ \p NodeTraits defines type traits for node.
+ See \ref node_traits for \p NodeTraits interface description
+
+ \p Options are:
+ - \p opt::gc - garbage collector
+ - \p opt::tag - a \ref cds_intrusive_hook_tag "tag"
+ */
+ template <typename NodeTraits, typename... Options >
+ struct traits_hook: public hook< opt::traits_hook_tag, Options... >
+ {
+ //@cond
+ typedef NodeTraits node_traits;
+ //@endcond
+ };
+
+ /// Option specifying random level generator
+ /**
+ The random level generator is an important part of skip-list algorithm.
+ The node height in the skip-list have a probabilistic distribution
+ where half of the nodes that have level \p i pointers also have level <tt>i+1</tt> pointers
+ (i = 0..30).
+ The random level generator should provide such distribution.
+
+ The \p Type functor interface is:
+ \code
+ struct random_generator {
+ static unsigned int const c_nUpperBound = 32;
+ random_generator();
+ unsigned int operator()();
+ };
+ \endcode
+
+ where
+ - \p c_nUpperBound - constant that specifies the upper bound of random number generated.
+ The generator produces a number from range <tt>[0 .. c_nUpperBound)</tt> (upper bound excluded).
+ \p c_nUpperBound must be no more than 32.
+ - <tt>random_generator()</tt> - the constructor of generator object initialises the generator instance (its internal state).
+ - <tt>unsigned int operator()()</tt> - the main generating function. Returns random level from range <tt>[0 .. c_nUpperBound - 1]</tt>
+
+
+ Stateful generators are supported.
+
+ Available \p Type implementations:
+ - \p skip_list::xor_shift
+ - \p skip_list::turbo
+ */
+ template <typename Type>
+ struct random_level_generator {
+ //@cond
+ template <typename Base>
+ struct pack: public Base
+ {
+ typedef Type random_level_generator;
+ };
+ //@endcond
+ };
+
+ /// Xor-shift random level generator
+ /**
+ The simplest of the generators described in George Marsaglia's "Xorshift RNGs" paper.
+ This is not a high-quality generator but is acceptable for skip-list.
+
+ The random generator should return numbers from range [0 .. MaxHeight - 1].
+
+ From Doug Lea's ConcurrentSkipListMap.java.
+ */
+ template <unsigned MaxHeight>
+ class xor_shift {
+ //@cond
+ atomics::atomic<unsigned int> m_nSeed;
+
+ static_assert( MaxHeight > 1, "MaxHeight" );
+ static_assert( MaxHeight <= c_nHeightLimit, "MaxHeight is too large" );
+ static unsigned int const c_nBitMask = (1u << ( MaxHeight - 1 )) - 1;
+ //@endcond
+
+ public:
+ /// The upper bound of generator's return value. The generator produces random number in range <tt>[0..c_nUpperBound)</tt>
+ static unsigned int const c_nUpperBound = MaxHeight;
+
+ /// Initializes the generator instance
+ xor_shift()
+ {
+ m_nSeed.store( (unsigned int) cds::OS::Timer::random_seed(), atomics::memory_order_relaxed );
+ }
+
+ /// Main generator function
+ unsigned int operator()()
+ {
+ /* ConcurrentSkipListMap.java
+ private int randomLevel() {
+ int x = randomSeed;
+ x ^= x << 13;
+ x ^= x >>> 17;
+ randomSeed = x ^= x << 5;
+ if ((x & 0x80000001) != 0) // test highest and lowest bits
+ return 0;
+ int level = 1;
+ while (((x >>>= 1) & 1) != 0) ++level;
+ return level;
+ }
+ */
+ unsigned int x = m_nSeed.load( atomics::memory_order_relaxed );
+ x ^= x << 13;
+ x ^= x >> 17;
+ x ^= x << 5;
+ m_nSeed.store( x, atomics::memory_order_relaxed );
+ unsigned int nLevel = ((x & 0x00000001) != 0) ? 0 : cds::bitop::LSB( (~(x >> 1)) & c_nBitMask );
+
+ assert( nLevel < c_nUpperBound );
+ return nLevel;
+ }
+ };
+
+ /// Xor-shift random level generator, max height 32
+ typedef xor_shift<c_nHeightLimit> xorshift32;
+
+ //@cond
+ // For backward compatibility
+ typedef xorshift32 xorshift;
+ //@endcond
+
+ /// \ref xor_shift generator, max height 24
+ typedef xor_shift< 24 > xorshift24;
+
+ /// \ref xor_shift generator, max height = 16
+ typedef xor_shift< 16 > xorshift16;
+
+ /// Turbo-pascal random level generator
+ /**
+ This uses a cheap pseudo-random function that was used in Turbo Pascal.
+
+ The random generator should return numbers from range [0..31].
+
+ From Doug Lea's ConcurrentSkipListMap.java.
+ */
+ template <unsigned MaxHeight>
+ class turbo
+ {
+ //@cond
+ atomics::atomic<unsigned int> m_nSeed;
+
+ static_assert( MaxHeight > 1, "MaxHeight" );
+ static_assert( MaxHeight <= c_nHeightLimit, "MaxHeight is too large" );
+ static unsigned int const c_nBitMask = (1u << ( MaxHeight - 1 )) - 1;
+ //@endcond
+ public:
+ /// The upper bound of generator's return value. The generator produces random number in range <tt>[0..c_nUpperBound)</tt>
+ static unsigned int const c_nUpperBound = MaxHeight;
+
+ /// Initializes the generator instance
+ turbo()
+ {
+ m_nSeed.store( (unsigned int) cds::OS::Timer::random_seed(), atomics::memory_order_relaxed );
+ }
+
+ /// Main generator function
+ unsigned int operator()()
+ {
+ /*
+ private int randomLevel() {
+ int level = 0;
+ int r = randomSeed;
+ randomSeed = r * 134775813 + 1;
+ if (r < 0) {
+ while ((r <<= 1) > 0)
+ ++level;
+ }
+ return level;
+ }
+ */
+ /*
+ The low bits are apparently not very random (the original used only
+ upper 16 bits) so we traverse from highest bit down (i.e., test
+ sign), thus hardly ever use lower bits.
+ */
+ unsigned int x = m_nSeed.load( atomics::memory_order_relaxed ) * 134775813 + 1;
+ m_nSeed.store( x, atomics::memory_order_relaxed );
+ unsigned int nLevel = ( x & 0x80000000 ) ? ( c_nUpperBound - 1 - cds::bitop::MSBnz( (x & c_nBitMask ) | 1 )) : 0;
+
+ assert( nLevel < c_nUpperBound );
+ return nLevel;
+ }
+ };
+
+ /// Turbo-Pascal random level generator, max height 32
+ typedef turbo<c_nHeightLimit> turbo32;
+
+ //@cond
+ // For backward compatibility
+ typedef turbo32 turbo_pascal;
+ //@endcond
+
+ /// Turbo-Pascal generator, max height 24
+ typedef turbo< 24 > turbo24;
+
+ /// Turbo-Pascal generator, max height 16
+ typedef turbo< 16 > turbo16;
+
+ /// \p SkipListSet internal statistics
+ template <typename EventCounter = cds::atomicity::event_counter>
+ struct stat {
+ typedef EventCounter event_counter ; ///< Event counter type
+
+ event_counter m_nNodeHeightAdd[c_nHeightLimit] ; ///< Count of added node of each height
+ event_counter m_nNodeHeightDel[c_nHeightLimit] ; ///< Count of deleted node of each height
+ event_counter m_nInsertSuccess ; ///< Count of success insertion
+ event_counter m_nInsertFailed ; ///< Count of failed insertion
+ event_counter m_nInsertRetries ; ///< Count of unsuccessful retries of insertion
+ event_counter m_nUpdateExist ; ///< Count of \p update() call for existed node
+ event_counter m_nUpdateNew ; ///< Count of \p update() call for new node
+ event_counter m_nUnlinkSuccess ; ///< Count of successful call of \p unlink
+ event_counter m_nUnlinkFailed ; ///< Count of failed call of \p unlink
+ event_counter m_nEraseSuccess ; ///< Count of successful call of \p erase
+ event_counter m_nEraseFailed ; ///< Count of failed call of \p erase
+ event_counter m_nEraseRetry ; ///< Count of retries while erasing node
+ event_counter m_nFindFastSuccess ; ///< Count of successful call of \p find and all derivatives (via fast-path)
+ event_counter m_nFindFastFailed ; ///< Count of failed call of \p find and all derivatives (via fast-path)
+ event_counter m_nFindSlowSuccess ; ///< Count of successful call of \p find and all derivatives (via slow-path)
+ event_counter m_nFindSlowFailed ; ///< Count of failed call of \p find and all derivatives (via slow-path)
+ event_counter m_nRenewInsertPosition ; ///< Count of renewing position events while inserting
+ event_counter m_nLogicDeleteWhileInsert; ///< Count of events "The node has been logically deleted while inserting"
+ event_counter m_nRemoveWhileInsert ; ///< Count of evnts "The node is removing while inserting"
+ event_counter m_nFastErase ; ///< Fast erase event counter
+ event_counter m_nFastExtract ; ///< Fast extract event counter
+ event_counter m_nSlowErase ; ///< Slow erase event counter
+ event_counter m_nSlowExtract ; ///< Slow extract event counter
+ event_counter m_nExtractSuccess ; ///< Count of successful call of \p extract
+ event_counter m_nExtractFailed ; ///< Count of failed call of \p extract
+ event_counter m_nExtractRetries ; ///< Count of retries of \p extract call
+ event_counter m_nExtractMinSuccess ; ///< Count of successful call of \p extract_min
+ event_counter m_nExtractMinFailed ; ///< Count of failed call of \p extract_min
+ event_counter m_nExtractMinRetries ; ///< Count of retries of \p extract_min call
+ event_counter m_nExtractMaxSuccess ; ///< Count of successful call of \p extract_max
+ event_counter m_nExtractMaxFailed ; ///< Count of failed call of \p extract_max
+ event_counter m_nExtractMaxRetries ; ///< Count of retries of \p extract_max call
+ event_counter m_nEraseWhileFind ; ///< Count of erased item while searching
+ event_counter m_nExtractWhileFind ; ///< Count of extracted item while searching (RCU only)
+ event_counter m_nMarkFailed ; ///< Count of failed node marking (logical deletion mark)
+ event_counter m_nEraseContention ; ///< Count of key erasing contention encountered
+
+ //@cond
+ void onAddNode( unsigned int nHeight )
+ {
+ assert( nHeight > 0 && nHeight <= sizeof(m_nNodeHeightAdd) / sizeof(m_nNodeHeightAdd[0]));
+ ++m_nNodeHeightAdd[nHeight - 1];
+ }
+ void onRemoveNode( unsigned int nHeight )
+ {
+ assert( nHeight > 0 && nHeight <= sizeof(m_nNodeHeightDel) / sizeof(m_nNodeHeightDel[0]));
+ ++m_nNodeHeightDel[nHeight - 1];
+ }
+
+ void onInsertSuccess() { ++m_nInsertSuccess ; }
+ void onInsertFailed() { ++m_nInsertFailed ; }
+ void onInsertRetry() { ++m_nInsertRetries ; }
+ void onUpdateExist() { ++m_nUpdateExist ; }
+ void onUpdateNew() { ++m_nUpdateNew ; }
+ void onUnlinkSuccess() { ++m_nUnlinkSuccess ; }
+ void onUnlinkFailed() { ++m_nUnlinkFailed ; }
+ void onEraseSuccess() { ++m_nEraseSuccess ; }
+ void onEraseFailed() { ++m_nEraseFailed ; }
+ void onEraseRetry() { ++m_nEraseRetry; }
+ void onFindFastSuccess() { ++m_nFindFastSuccess ; }
+ void onFindFastFailed() { ++m_nFindFastFailed ; }
+ void onFindSlowSuccess() { ++m_nFindSlowSuccess ; }
+ void onFindSlowFailed() { ++m_nFindSlowFailed ; }
+ void onEraseWhileFind() { ++m_nEraseWhileFind ; }
+ void onExtractWhileFind() { ++m_nExtractWhileFind ; }
+ void onRenewInsertPosition() { ++m_nRenewInsertPosition; }
+ void onLogicDeleteWhileInsert() { ++m_nLogicDeleteWhileInsert; }
+ void onRemoveWhileInsert() { ++m_nRemoveWhileInsert; }
+ void onFastErase() { ++m_nFastErase; }
+ void onFastExtract() { ++m_nFastExtract; }
+ void onSlowErase() { ++m_nSlowErase; }
+ void onSlowExtract() { ++m_nSlowExtract; }
+ void onExtractSuccess() { ++m_nExtractSuccess; }
+ void onExtractFailed() { ++m_nExtractFailed; }
+ void onExtractRetry() { ++m_nExtractRetries; }
+ void onExtractMinSuccess() { ++m_nExtractMinSuccess; }
+ void onExtractMinFailed() { ++m_nExtractMinFailed; }
+ void onExtractMinRetry() { ++m_nExtractMinRetries; }
+ void onExtractMaxSuccess() { ++m_nExtractMaxSuccess; }
+ void onExtractMaxFailed() { ++m_nExtractMaxFailed; }
+ void onExtractMaxRetry() { ++m_nExtractMaxRetries; }
+ void onMarkFailed() { ++m_nMarkFailed; }
+ void onEraseContention() { ++m_nEraseContention; }
+ //@endcond
+ };
+
+ /// \p SkipListSet empty internal statistics
+ struct empty_stat {
+ //@cond
+ void onAddNode( unsigned int /*nHeight*/ ) const {}
+ void onRemoveNode( unsigned int /*nHeight*/ ) const {}
+ void onInsertSuccess() const {}
+ void onInsertFailed() const {}
+ void onInsertRetry() const {}
+ void onUpdateExist() const {}
+ void onUpdateNew() const {}
+ void onUnlinkSuccess() const {}
+ void onUnlinkFailed() const {}
+ void onEraseSuccess() const {}
+ void onEraseFailed() const {}
+ void onEraseRetry() const {}
+ void onFindFastSuccess() const {}
+ void onFindFastFailed() const {}
+ void onFindSlowSuccess() const {}
+ void onFindSlowFailed() const {}
+ void onEraseWhileFind() const {}
+ void onExtractWhileFind() const {}
+ void onRenewInsertPosition() const {}
+ void onLogicDeleteWhileInsert() const {}
+ void onRemoveWhileInsert() const {}
+ void onFastErase() const {}
+ void onFastExtract() const {}
+ void onSlowErase() const {}
+ void onSlowExtract() const {}
+ void onExtractSuccess() const {}
+ void onExtractFailed() const {}
+ void onExtractRetry() const {}
+ void onExtractMinSuccess() const {}
+ void onExtractMinFailed() const {}
+ void onExtractMinRetry() const {}
+ void onExtractMaxSuccess() const {}
+ void onExtractMaxFailed() const {}
+ void onExtractMaxRetry() const {}
+ void onMarkFailed() const {}
+ void onEraseContention() const {}
+ //@endcond
+ };
+
+ //@cond
+ // For internal use only!!!
+ template <typename Type>
+ struct internal_node_builder {
+ template <typename Base>
+ struct pack: public Base
+ {
+ typedef Type internal_node_builder;
+ };
+ };
+ //@endcond
+
+ /// \p SkipListSet traits
+ struct traits
+ {
+ /// Hook used
+ /**
+ Possible values are: \p skip_list::base_hook, \p skip_list::member_hook, \p skip_list::traits_hook.
+ */
+ typedef base_hook<> hook;
+
+ /// Key comparison functor
+ /**
+ No default functor is provided. If the option is not specified, the \p less is used.
+ */
+ typedef opt::none compare;
+
+ /// specifies binary predicate used for key compare.
+ /**
+ Default is \p std::less<T>.
+ */
+ typedef opt::none less;
+
+ /// Disposer
+ /**
+ The functor used for dispose removed items. Default is \p opt::v::empty_disposer.
+ */
+ typedef opt::v::empty_disposer disposer;
+
+ /// Item counter
+ /**
+ The type for item counting feature.
+ By default, item counting is disabled (\p atomicity::empty_item_counter),
+ \p atomicity::item_counter or \p atomicity::cache_friendly_item_counter enables it.
+ */
+ typedef atomicity::empty_item_counter item_counter;
+
+ /// C++ memory ordering model
+ /**
+ List of available memory ordering see \p opt::memory_model
+ */
+ typedef opt::v::relaxed_ordering memory_model;
+
+ /// Random level generator
+ /**
+ The random level generator is an important part of skip-list algorithm.
+ The node height in the skip-list have a probabilistic distribution
+ where half of the nodes that have level \p i pointers also have level <tt>i+1</tt> pointers
+ (i = 0..30). So, the height of a node is in range [0..31].
+
+ See \p skip_list::random_level_generator option setter.
+ */
+ typedef turbo32 random_level_generator;
+
+ /// Allocator
+ /**
+ Although the skip-list is an intrusive container,
+ an allocator should be provided to maintain variable randomly-calculated height of the node
+ since the node can contain up to 32 next pointers.
+ The allocator specified is used to allocate an array of next pointers
+ for nodes which height is more than 1.
+ */
+ typedef CDS_DEFAULT_ALLOCATOR allocator;
+
+ /// back-off strategy
+ /**
+ If the option is not specified, the \p cds::backoff::Default is used.
+ */
+ typedef cds::backoff::Default back_off;
+
+ /// Internal statistics
+ /**
+ By default, internal statistics is disabled (\p skip_list::empty_stat).
+ Use \p skip_list::stat to enable it.
+ */
+ typedef empty_stat stat;
+
+ /// RCU deadlock checking policy (only for \ref cds_intrusive_SkipListSet_rcu "RCU-based SkipListSet")
+ /**
+ List of available options see \p opt::rcu_check_deadlock
+ */
+ typedef opt::v::rcu_throw_deadlock rcu_check_deadlock;
+
+ //@cond
+ // For internal use only!!!
+ typedef opt::none internal_node_builder;
+ //@endcond
+ };
+
+ /// Metafunction converting option list to \p SkipListSet traits
+ /**
+ \p Options are:
+ - \p opt::hook - hook used. Possible values are: \p skip_list::base_hook, \p skip_list::member_hook, \p skip_list::traits_hook.
+ If the option is not specified, <tt>skip_list::base_hook<></tt> and \p gc::HP is used.
+ - \p opt::compare - key comparison functor. No default functor is provided.
+ If the option is not specified, the \p opt::less is used.
+ - \p opt::less - specifies binary predicate used for key comparison. Default is \p std::less<T>.
+ - \p opt::disposer - the functor used for dispose removed items. Default is \p opt::v::empty_disposer. Due the nature
+ of GC schema the disposer may be called asynchronously.
+ - \p opt::item_counter - the type of item counting feature. Default is disabled, i.e. \p atomicity::empty_item_counter.
+ To enable it use \p atomicity::item_counter or \p atomicity::cache_friendly_item_counter
+ - \p opt::memory_model - C++ memory ordering model. Can be \p opt::v::relaxed_ordering (relaxed memory model, the default)
+ or \p opt::v::sequential_consistent (sequentially consisnent memory model).
+ - \p skip_list::random_level_generator - random level generator. Can be \p skip_list::xor_shift,
+ \p skip_list::turbo32 (the default) or user-provided one.
+ See \p skip_list::random_level_generator option description for explanation.
+ - \p opt::allocator - although the skip-list is an intrusive container,
+ an allocator should be provided to maintain variable randomly-calculated height of the node
+ since the node can contain up to 32 next pointers. The allocator option is used to allocate an array of next pointers
+ for nodes which height is more than 1. Default is \ref CDS_DEFAULT_ALLOCATOR.
+ - \p opt::back_off - back-off strategy, default is \p cds::backoff::Default.
+ - \p opt::stat - internal statistics. By default, it is disabled (\p skip_list::empty_stat).
+ To enable it use \p skip_list::stat
+ */
+ template <typename... Options>
+ struct make_traits {
+# ifdef CDS_DOXYGEN_INVOKED
+ typedef implementation_defined type ; ///< Metafunction result
+# else
+ typedef typename cds::opt::make_options<
+ typename cds::opt::find_type_traits< traits, Options... >::type
+ ,Options...
+ >::type type;
+# endif
+ };
+
+ //@cond
+ namespace details {
+ template <typename Node>
+ class head_node: public Node
+ {
+ typedef Node node_type;
+ typename node_type::atomic_marked_ptr m_Tower[skip_list::c_nHeightLimit];
+
+ public:
+ head_node( unsigned int nHeight )
+ {
+ for ( size_t i = 0; i < sizeof(m_Tower) / sizeof(m_Tower[0]); ++i )
+ m_Tower[i].store( typename node_type::marked_ptr(), atomics::memory_order_relaxed );
+
+ node_type::make_tower( nHeight, m_Tower );
+ }
+
+ node_type * head() const
+ {
+ return const_cast<node_type *>( static_cast<node_type const *>(this));
+ }
+ };
+
+ template <typename NodeType, typename AtomicNodePtr, typename Alloc>
+ struct intrusive_node_builder
+ {
+ typedef NodeType node_type;
+ typedef AtomicNodePtr atomic_node_ptr;
+ typedef Alloc allocator_type;
+
+ typedef cds::details::Allocator< atomic_node_ptr, allocator_type > tower_allocator;
+
+ template <typename RandomGen>
+ static node_type * make_tower( node_type * pNode, RandomGen& gen )
+ {
+ return make_tower( pNode, gen() + 1 );
+ }
+
+ static node_type * make_tower( node_type * pNode, unsigned int nHeight )
+ {
+ if ( nHeight > 1 )
+ pNode->make_tower( nHeight, tower_allocator().NewArray( nHeight - 1, nullptr ));
+ return pNode;
+ }
+
+ static void dispose_tower( node_type * pNode )
+ {
+ unsigned int nHeight = pNode->height();
+ if ( nHeight > 1 )
+ tower_allocator().Delete( pNode->release_tower(), nHeight );
+ }
+
+ struct node_disposer {
+ void operator()( node_type * pNode )
+ {
+ dispose_tower( pNode );
+ }
+ };
+ };
+
+ // Forward declaration
+ template <class GC, typename NodeTraits, typename BackOff, bool IsConst>
+ class iterator;
+
+ } // namespace details
+ //@endcond
+
+ } // namespace skip_list
+
+ // Forward declaration
+ template <class GC, typename T, typename Traits = skip_list::traits >
+ class SkipListSet;
+
+}} // namespace cds::intrusive
+
+#endif // #ifndef CDSLIB_INTRUSIVE_DETAILS_SKIP_LIST_BASE_H
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