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// Provides an efficient blocking version of moodycamel::ConcurrentQueue.
// ©2015-2020 Cameron Desrochers. Distributed under the terms of the simplified
// BSD license, available at the top of concurrentqueue.h.
// Also dual-licensed under the Boost Software License (see LICENSE.md)
// Uses Jeff Preshing's semaphore implementation (under the terms of its
// separate zlib license, see lightweightsemaphore.h).
#pragma once
#include "concurrentqueue.h"
#include "lightweightsemaphore.h"
#include <type_traits>
#include <cerrno>
#include <memory>
#include <chrono>
#include <ctime>
namespace moodycamel{// This is a blocking version of the queue. It has an almost identical interface to
// the normal non-blocking version, with the addition of various wait_dequeue() methods
// and the removal of producer-specific dequeue methods.
template<typename T, typename Traits = ConcurrentQueueDefaultTraits>class BlockingConcurrentQueue{private: typedef ::moodycamel::ConcurrentQueue<T, Traits> ConcurrentQueue; typedef ::moodycamel::LightweightSemaphore LightweightSemaphore;
public: typedef typename ConcurrentQueue::producer_token_t producer_token_t; typedef typename ConcurrentQueue::consumer_token_t consumer_token_t; typedef typename ConcurrentQueue::index_t index_t; typedef typename ConcurrentQueue::size_t size_t; typedef typename std::make_signed<size_t>::type ssize_t; static const size_t BLOCK_SIZE = ConcurrentQueue::BLOCK_SIZE; static const size_t EXPLICIT_BLOCK_EMPTY_COUNTER_THRESHOLD = ConcurrentQueue::EXPLICIT_BLOCK_EMPTY_COUNTER_THRESHOLD; static const size_t EXPLICIT_INITIAL_INDEX_SIZE = ConcurrentQueue::EXPLICIT_INITIAL_INDEX_SIZE; static const size_t IMPLICIT_INITIAL_INDEX_SIZE = ConcurrentQueue::IMPLICIT_INITIAL_INDEX_SIZE; static const size_t INITIAL_IMPLICIT_PRODUCER_HASH_SIZE = ConcurrentQueue::INITIAL_IMPLICIT_PRODUCER_HASH_SIZE; static const std::uint32_t EXPLICIT_CONSUMER_CONSUMPTION_QUOTA_BEFORE_ROTATE = ConcurrentQueue::EXPLICIT_CONSUMER_CONSUMPTION_QUOTA_BEFORE_ROTATE; static const size_t MAX_SUBQUEUE_SIZE = ConcurrentQueue::MAX_SUBQUEUE_SIZE; public: // Creates a queue with at least `capacity` element slots; note that the
// actual number of elements that can be inserted without additional memory
// allocation depends on the number of producers and the block size (e.g. if
// the block size is equal to `capacity`, only a single block will be allocated
// up-front, which means only a single producer will be able to enqueue elements
// without an extra allocation -- blocks aren't shared between producers).
// This method is not thread safe -- it is up to the user to ensure that the
// queue is fully constructed before it starts being used by other threads (this
// includes making the memory effects of construction visible, possibly with a
// memory barrier).
explicit BlockingConcurrentQueue(size_t capacity = 6 * BLOCK_SIZE) : inner(capacity), sema(create<LightweightSemaphore, ssize_t, int>(0, (int)Traits::MAX_SEMA_SPINS), &BlockingConcurrentQueue::template destroy<LightweightSemaphore>) { assert(reinterpret_cast<ConcurrentQueue*>((BlockingConcurrentQueue*)1) == &((BlockingConcurrentQueue*)1)->inner && "BlockingConcurrentQueue must have ConcurrentQueue as its first member"); if (!sema) { MOODYCAMEL_THROW(std::bad_alloc()); } } BlockingConcurrentQueue(size_t minCapacity, size_t maxExplicitProducers, size_t maxImplicitProducers) : inner(minCapacity, maxExplicitProducers, maxImplicitProducers), sema(create<LightweightSemaphore, ssize_t, int>(0, (int)Traits::MAX_SEMA_SPINS), &BlockingConcurrentQueue::template destroy<LightweightSemaphore>) { assert(reinterpret_cast<ConcurrentQueue*>((BlockingConcurrentQueue*)1) == &((BlockingConcurrentQueue*)1)->inner && "BlockingConcurrentQueue must have ConcurrentQueue as its first member"); if (!sema) { MOODYCAMEL_THROW(std::bad_alloc()); } } // Disable copying and copy assignment
BlockingConcurrentQueue(BlockingConcurrentQueue const&) MOODYCAMEL_DELETE_FUNCTION; BlockingConcurrentQueue& operator=(BlockingConcurrentQueue const&) MOODYCAMEL_DELETE_FUNCTION; // Moving is supported, but note that it is *not* a thread-safe operation.
// Nobody can use the queue while it's being moved, and the memory effects
// of that move must be propagated to other threads before they can use it.
// Note: When a queue is moved, its tokens are still valid but can only be
// used with the destination queue (i.e. semantically they are moved along
// with the queue itself).
BlockingConcurrentQueue(BlockingConcurrentQueue&& other) MOODYCAMEL_NOEXCEPT : inner(std::move(other.inner)), sema(std::move(other.sema)) { } inline BlockingConcurrentQueue& operator=(BlockingConcurrentQueue&& other) MOODYCAMEL_NOEXCEPT { return swap_internal(other); } // Swaps this queue's state with the other's. Not thread-safe.
// Swapping two queues does not invalidate their tokens, however
// the tokens that were created for one queue must be used with
// only the swapped queue (i.e. the tokens are tied to the
// queue's movable state, not the object itself).
inline void swap(BlockingConcurrentQueue& other) MOODYCAMEL_NOEXCEPT { swap_internal(other); } private: BlockingConcurrentQueue& swap_internal(BlockingConcurrentQueue& other) { if (this == &other) { return *this; } inner.swap(other.inner); sema.swap(other.sema); return *this; } public: // Enqueues a single item (by copying it).
// Allocates memory if required. Only fails if memory allocation fails (or implicit
// production is disabled because Traits::INITIAL_IMPLICIT_PRODUCER_HASH_SIZE is 0,
// or Traits::MAX_SUBQUEUE_SIZE has been defined and would be surpassed).
// Thread-safe.
inline bool enqueue(T const& item) { if ((details::likely)(inner.enqueue(item))) { sema->signal(); return true; } return false; } // Enqueues a single item (by moving it, if possible).
// Allocates memory if required. Only fails if memory allocation fails (or implicit
// production is disabled because Traits::INITIAL_IMPLICIT_PRODUCER_HASH_SIZE is 0,
// or Traits::MAX_SUBQUEUE_SIZE has been defined and would be surpassed).
// Thread-safe.
inline bool enqueue(T&& item) { if ((details::likely)(inner.enqueue(std::move(item)))) { sema->signal(); return true; } return false; } // Enqueues a single item (by copying it) using an explicit producer token.
// Allocates memory if required. Only fails if memory allocation fails (or
// Traits::MAX_SUBQUEUE_SIZE has been defined and would be surpassed).
// Thread-safe.
inline bool enqueue(producer_token_t const& token, T const& item) { if ((details::likely)(inner.enqueue(token, item))) { sema->signal(); return true; } return false; } // Enqueues a single item (by moving it, if possible) using an explicit producer token.
// Allocates memory if required. Only fails if memory allocation fails (or
// Traits::MAX_SUBQUEUE_SIZE has been defined and would be surpassed).
// Thread-safe.
inline bool enqueue(producer_token_t const& token, T&& item) { if ((details::likely)(inner.enqueue(token, std::move(item)))) { sema->signal(); return true; } return false; } // Enqueues several items.
// Allocates memory if required. Only fails if memory allocation fails (or
// implicit production is disabled because Traits::INITIAL_IMPLICIT_PRODUCER_HASH_SIZE
// is 0, or Traits::MAX_SUBQUEUE_SIZE has been defined and would be surpassed).
// Note: Use std::make_move_iterator if the elements should be moved instead of copied.
// Thread-safe.
template<typename It> inline bool enqueue_bulk(It itemFirst, size_t count) { if ((details::likely)(inner.enqueue_bulk(std::forward<It>(itemFirst), count))) { sema->signal((LightweightSemaphore::ssize_t)(ssize_t)count); return true; } return false; } // Enqueues several items using an explicit producer token.
// Allocates memory if required. Only fails if memory allocation fails
// (or Traits::MAX_SUBQUEUE_SIZE has been defined and would be surpassed).
// Note: Use std::make_move_iterator if the elements should be moved
// instead of copied.
// Thread-safe.
template<typename It> inline bool enqueue_bulk(producer_token_t const& token, It itemFirst, size_t count) { if ((details::likely)(inner.enqueue_bulk(token, std::forward<It>(itemFirst), count))) { sema->signal((LightweightSemaphore::ssize_t)(ssize_t)count); return true; } return false; } // Enqueues a single item (by copying it).
// Does not allocate memory. Fails if not enough room to enqueue (or implicit
// production is disabled because Traits::INITIAL_IMPLICIT_PRODUCER_HASH_SIZE
// is 0).
// Thread-safe.
inline bool try_enqueue(T const& item) { if (inner.try_enqueue(item)) { sema->signal(); return true; } return false; } // Enqueues a single item (by moving it, if possible).
// Does not allocate memory (except for one-time implicit producer).
// Fails if not enough room to enqueue (or implicit production is
// disabled because Traits::INITIAL_IMPLICIT_PRODUCER_HASH_SIZE is 0).
// Thread-safe.
inline bool try_enqueue(T&& item) { if (inner.try_enqueue(std::move(item))) { sema->signal(); return true; } return false; } // Enqueues a single item (by copying it) using an explicit producer token.
// Does not allocate memory. Fails if not enough room to enqueue.
// Thread-safe.
inline bool try_enqueue(producer_token_t const& token, T const& item) { if (inner.try_enqueue(token, item)) { sema->signal(); return true; } return false; } // Enqueues a single item (by moving it, if possible) using an explicit producer token.
// Does not allocate memory. Fails if not enough room to enqueue.
// Thread-safe.
inline bool try_enqueue(producer_token_t const& token, T&& item) { if (inner.try_enqueue(token, std::move(item))) { sema->signal(); return true; } return false; } // Enqueues several items.
// Does not allocate memory (except for one-time implicit producer).
// Fails if not enough room to enqueue (or implicit production is
// disabled because Traits::INITIAL_IMPLICIT_PRODUCER_HASH_SIZE is 0).
// Note: Use std::make_move_iterator if the elements should be moved
// instead of copied.
// Thread-safe.
template<typename It> inline bool try_enqueue_bulk(It itemFirst, size_t count) { if (inner.try_enqueue_bulk(std::forward<It>(itemFirst), count)) { sema->signal((LightweightSemaphore::ssize_t)(ssize_t)count); return true; } return false; } // Enqueues several items using an explicit producer token.
// Does not allocate memory. Fails if not enough room to enqueue.
// Note: Use std::make_move_iterator if the elements should be moved
// instead of copied.
// Thread-safe.
template<typename It> inline bool try_enqueue_bulk(producer_token_t const& token, It itemFirst, size_t count) { if (inner.try_enqueue_bulk(token, std::forward<It>(itemFirst), count)) { sema->signal((LightweightSemaphore::ssize_t)(ssize_t)count); return true; } return false; } // Attempts to dequeue from the queue.
// Returns false if all producer streams appeared empty at the time they
// were checked (so, the queue is likely but not guaranteed to be empty).
// Never allocates. Thread-safe.
template<typename U> inline bool try_dequeue(U& item) { if (sema->tryWait()) { while (!inner.try_dequeue(item)) { continue; } return true; } return false; } // Attempts to dequeue from the queue using an explicit consumer token.
// Returns false if all producer streams appeared empty at the time they
// were checked (so, the queue is likely but not guaranteed to be empty).
// Never allocates. Thread-safe.
template<typename U> inline bool try_dequeue(consumer_token_t& token, U& item) { if (sema->tryWait()) { while (!inner.try_dequeue(token, item)) { continue; } return true; } return false; } // Attempts to dequeue several elements from the queue.
// Returns the number of items actually dequeued.
// Returns 0 if all producer streams appeared empty at the time they
// were checked (so, the queue is likely but not guaranteed to be empty).
// Never allocates. Thread-safe.
template<typename It> inline size_t try_dequeue_bulk(It itemFirst, size_t max) { size_t count = 0; max = (size_t)sema->tryWaitMany((LightweightSemaphore::ssize_t)(ssize_t)max); while (count != max) { count += inner.template try_dequeue_bulk<It&>(itemFirst, max - count); } return count; } // Attempts to dequeue several elements from the queue using an explicit consumer token.
// Returns the number of items actually dequeued.
// Returns 0 if all producer streams appeared empty at the time they
// were checked (so, the queue is likely but not guaranteed to be empty).
// Never allocates. Thread-safe.
template<typename It> inline size_t try_dequeue_bulk(consumer_token_t& token, It itemFirst, size_t max) { size_t count = 0; max = (size_t)sema->tryWaitMany((LightweightSemaphore::ssize_t)(ssize_t)max); while (count != max) { count += inner.template try_dequeue_bulk<It&>(token, itemFirst, max - count); } return count; } // Blocks the current thread until there's something to dequeue, then
// dequeues it.
// Never allocates. Thread-safe.
template<typename U> inline void wait_dequeue(U& item) { while (!sema->wait()) { continue; } while (!inner.try_dequeue(item)) { continue; } }
// Blocks the current thread until either there's something to dequeue
// or the timeout (specified in microseconds) expires. Returns false
// without setting `item` if the timeout expires, otherwise assigns
// to `item` and returns true.
// Using a negative timeout indicates an indefinite timeout,
// and is thus functionally equivalent to calling wait_dequeue.
// Never allocates. Thread-safe.
template<typename U> inline bool wait_dequeue_timed(U& item, std::int64_t timeout_usecs) { if (!sema->wait(timeout_usecs)) { return false; } while (!inner.try_dequeue(item)) { continue; } return true; } // Blocks the current thread until either there's something to dequeue
// or the timeout expires. Returns false without setting `item` if the
// timeout expires, otherwise assigns to `item` and returns true.
// Never allocates. Thread-safe.
template<typename U, typename Rep, typename Period> inline bool wait_dequeue_timed(U& item, std::chrono::duration<Rep, Period> const& timeout) { return wait_dequeue_timed(item, std::chrono::duration_cast<std::chrono::microseconds>(timeout).count()); } // Blocks the current thread until there's something to dequeue, then
// dequeues it using an explicit consumer token.
// Never allocates. Thread-safe.
template<typename U> inline void wait_dequeue(consumer_token_t& token, U& item) { while (!sema->wait()) { continue; } while (!inner.try_dequeue(token, item)) { continue; } } // Blocks the current thread until either there's something to dequeue
// or the timeout (specified in microseconds) expires. Returns false
// without setting `item` if the timeout expires, otherwise assigns
// to `item` and returns true.
// Using a negative timeout indicates an indefinite timeout,
// and is thus functionally equivalent to calling wait_dequeue.
// Never allocates. Thread-safe.
template<typename U> inline bool wait_dequeue_timed(consumer_token_t& token, U& item, std::int64_t timeout_usecs) { if (!sema->wait(timeout_usecs)) { return false; } while (!inner.try_dequeue(token, item)) { continue; } return true; } // Blocks the current thread until either there's something to dequeue
// or the timeout expires. Returns false without setting `item` if the
// timeout expires, otherwise assigns to `item` and returns true.
// Never allocates. Thread-safe.
template<typename U, typename Rep, typename Period> inline bool wait_dequeue_timed(consumer_token_t& token, U& item, std::chrono::duration<Rep, Period> const& timeout) { return wait_dequeue_timed(token, item, std::chrono::duration_cast<std::chrono::microseconds>(timeout).count()); } // Attempts to dequeue several elements from the queue.
// Returns the number of items actually dequeued, which will
// always be at least one (this method blocks until the queue
// is non-empty) and at most max.
// Never allocates. Thread-safe.
template<typename It> inline size_t wait_dequeue_bulk(It itemFirst, size_t max) { size_t count = 0; max = (size_t)sema->waitMany((LightweightSemaphore::ssize_t)(ssize_t)max); while (count != max) { count += inner.template try_dequeue_bulk<It&>(itemFirst, max - count); } return count; } // Attempts to dequeue several elements from the queue.
// Returns the number of items actually dequeued, which can
// be 0 if the timeout expires while waiting for elements,
// and at most max.
// Using a negative timeout indicates an indefinite timeout,
// and is thus functionally equivalent to calling wait_dequeue_bulk.
// Never allocates. Thread-safe.
template<typename It> inline size_t wait_dequeue_bulk_timed(It itemFirst, size_t max, std::int64_t timeout_usecs) { size_t count = 0; max = (size_t)sema->waitMany((LightweightSemaphore::ssize_t)(ssize_t)max, timeout_usecs); while (count != max) { count += inner.template try_dequeue_bulk<It&>(itemFirst, max - count); } return count; } // Attempts to dequeue several elements from the queue.
// Returns the number of items actually dequeued, which can
// be 0 if the timeout expires while waiting for elements,
// and at most max.
// Never allocates. Thread-safe.
template<typename It, typename Rep, typename Period> inline size_t wait_dequeue_bulk_timed(It itemFirst, size_t max, std::chrono::duration<Rep, Period> const& timeout) { return wait_dequeue_bulk_timed<It&>(itemFirst, max, std::chrono::duration_cast<std::chrono::microseconds>(timeout).count()); } // Attempts to dequeue several elements from the queue using an explicit consumer token.
// Returns the number of items actually dequeued, which will
// always be at least one (this method blocks until the queue
// is non-empty) and at most max.
// Never allocates. Thread-safe.
template<typename It> inline size_t wait_dequeue_bulk(consumer_token_t& token, It itemFirst, size_t max) { size_t count = 0; max = (size_t)sema->waitMany((LightweightSemaphore::ssize_t)(ssize_t)max); while (count != max) { count += inner.template try_dequeue_bulk<It&>(token, itemFirst, max - count); } return count; } // Attempts to dequeue several elements from the queue using an explicit consumer token.
// Returns the number of items actually dequeued, which can
// be 0 if the timeout expires while waiting for elements,
// and at most max.
// Using a negative timeout indicates an indefinite timeout,
// and is thus functionally equivalent to calling wait_dequeue_bulk.
// Never allocates. Thread-safe.
template<typename It> inline size_t wait_dequeue_bulk_timed(consumer_token_t& token, It itemFirst, size_t max, std::int64_t timeout_usecs) { size_t count = 0; max = (size_t)sema->waitMany((LightweightSemaphore::ssize_t)(ssize_t)max, timeout_usecs); while (count != max) { count += inner.template try_dequeue_bulk<It&>(token, itemFirst, max - count); } return count; } // Attempts to dequeue several elements from the queue using an explicit consumer token.
// Returns the number of items actually dequeued, which can
// be 0 if the timeout expires while waiting for elements,
// and at most max.
// Never allocates. Thread-safe.
template<typename It, typename Rep, typename Period> inline size_t wait_dequeue_bulk_timed(consumer_token_t& token, It itemFirst, size_t max, std::chrono::duration<Rep, Period> const& timeout) { return wait_dequeue_bulk_timed<It&>(token, itemFirst, max, std::chrono::duration_cast<std::chrono::microseconds>(timeout).count()); } // Returns an estimate of the total number of elements currently in the queue. This
// estimate is only accurate if the queue has completely stabilized before it is called
// (i.e. all enqueue and dequeue operations have completed and their memory effects are
// visible on the calling thread, and no further operations start while this method is
// being called).
// Thread-safe.
inline size_t size_approx() const { return (size_t)sema->availableApprox(); } // Returns true if the underlying atomic variables used by
// the queue are lock-free (they should be on most platforms).
// Thread-safe.
static constexpr bool is_lock_free() { return ConcurrentQueue::is_lock_free(); }
private: template<typename U, typename A1, typename A2> static inline U* create(A1&& a1, A2&& a2) { void* p = (Traits::malloc)(sizeof(U)); return p != nullptr ? new (p) U(std::forward<A1>(a1), std::forward<A2>(a2)) : nullptr; } template<typename U> static inline void destroy(U* p) { if (p != nullptr) { p->~U(); } (Traits::free)(p); } private: ConcurrentQueue inner; std::unique_ptr<LightweightSemaphore, void (*)(LightweightSemaphore*)> sema;};
template<typename T, typename Traits>inline void swap(BlockingConcurrentQueue<T, Traits>& a, BlockingConcurrentQueue<T, Traits>& b) MOODYCAMEL_NOEXCEPT{ a.swap(b);}
} // end namespace moodycamel
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