// Provides an efficient blocking version of moodycamel::ConcurrentQueue. // ©2015-2016 Cameron Desrochers. Distributed under the terms of the simplified // BSD license, available at the top of concurrentqueue.h. // Uses Jeff Preshing's semaphore implementation (under the terms of its // separate zlib license, embedded below). #pragma once #include "concurrentqueue.h" #include #include #include #include #include #if defined(_WIN32) // Avoid including windows.h in a header; we only need a handful of // items, so we'll redeclare them here (this is relatively safe since // the API generally has to remain stable between Windows versions). // I know this is an ugly hack but it still beats polluting the global // namespace with thousands of generic names or adding a .cpp for nothing. extern "C" { struct _SECURITY_ATTRIBUTES; __declspec(dllimport) void* __stdcall CreateSemaphoreW(_SECURITY_ATTRIBUTES* lpSemaphoreAttributes, long lInitialCount, long lMaximumCount, const wchar_t* lpName); __declspec(dllimport) int __stdcall CloseHandle(void* hObject); __declspec(dllimport) unsigned long __stdcall WaitForSingleObject(void* hHandle, unsigned long dwMilliseconds); __declspec(dllimport) int __stdcall ReleaseSemaphore(void* hSemaphore, long lReleaseCount, long* lpPreviousCount); } #elif defined(__MACH__) #include #elif defined(__unix__) #include #endif namespace moodycamel { namespace details { // Code in the mpmc_sema namespace below is an adaptation of Jeff Preshing's // portable + lightweight semaphore implementations, originally from // https://github.com/preshing/cpp11-on-multicore/blob/master/common/sema.h // LICENSE: // Copyright (c) 2015 Jeff Preshing // // This software is provided 'as-is', without any express or implied // warranty. In no event will the authors be held liable for any damages // arising from the use of this software. // // Permission is granted to anyone to use this software for any purpose, // including commercial applications, and to alter it and redistribute it // freely, subject to the following restrictions: // // 1. The origin of this software must not be misrepresented; you must not // claim that you wrote the original software. If you use this software // in a product, an acknowledgement in the product documentation would be // appreciated but is not required. // 2. Altered source versions must be plainly marked as such, and must not be // misrepresented as being the original software. // 3. This notice may not be removed or altered from any source distribution. namespace mpmc_sema { #if defined(_WIN32) class Semaphore { private: void* m_hSema; Semaphore(const Semaphore& other) MOODYCAMEL_DELETE_FUNCTION; Semaphore& operator=(const Semaphore& other) MOODYCAMEL_DELETE_FUNCTION; public: Semaphore(int initialCount = 0) { assert(initialCount >= 0); const long maxLong = 0x7fffffff; m_hSema = CreateSemaphoreW(nullptr, initialCount, maxLong, nullptr); } ~Semaphore() { CloseHandle(m_hSema); } void wait() { const unsigned long infinite = 0xffffffff; WaitForSingleObject(m_hSema, infinite); } bool try_wait() { const unsigned long RC_WAIT_TIMEOUT = 0x00000102; return WaitForSingleObject(m_hSema, 0) != RC_WAIT_TIMEOUT; } bool timed_wait(std::uint64_t usecs) { const unsigned long RC_WAIT_TIMEOUT = 0x00000102; return WaitForSingleObject(m_hSema, (unsigned long)(usecs / 1000)) != RC_WAIT_TIMEOUT; } void signal(int count = 1) { ReleaseSemaphore(m_hSema, count, nullptr); } }; #elif defined(__MACH__) //--------------------------------------------------------- // Semaphore (Apple iOS and OSX) // Can't use POSIX semaphores due to http://lists.apple.com/archives/darwin-kernel/2009/Apr/msg00010.html //--------------------------------------------------------- class Semaphore { private: semaphore_t m_sema; Semaphore(const Semaphore& other) MOODYCAMEL_DELETE_FUNCTION; Semaphore& operator=(const Semaphore& other) MOODYCAMEL_DELETE_FUNCTION; public: Semaphore(int initialCount = 0) { assert(initialCount >= 0); semaphore_create(mach_task_self(), &m_sema, SYNC_POLICY_FIFO, initialCount); } ~Semaphore() { semaphore_destroy(mach_task_self(), m_sema); } void wait() { semaphore_wait(m_sema); } bool try_wait() { return timed_wait(0); } bool timed_wait(std::uint64_t timeout_usecs) { mach_timespec_t ts; ts.tv_sec = timeout_usecs / 1000000; ts.tv_nsec = (timeout_usecs % 1000000) * 1000; // added in OSX 10.10: https://developer.apple.com/library/prerelease/mac/documentation/General/Reference/APIDiffsMacOSX10_10SeedDiff/modules/Darwin.html kern_return_t rc = semaphore_timedwait(m_sema, ts); return rc != KERN_OPERATION_TIMED_OUT; } void signal() { semaphore_signal(m_sema); } void signal(int count) { while (count-- > 0) { semaphore_signal(m_sema); } } }; #elif defined(__unix__) //--------------------------------------------------------- // Semaphore (POSIX, Linux) //--------------------------------------------------------- class Semaphore { private: sem_t m_sema; Semaphore(const Semaphore& other) MOODYCAMEL_DELETE_FUNCTION; Semaphore& operator=(const Semaphore& other) MOODYCAMEL_DELETE_FUNCTION; public: Semaphore(int initialCount = 0) { assert(initialCount >= 0); sem_init(&m_sema, 0, initialCount); } ~Semaphore() { sem_destroy(&m_sema); } void wait() { // http://stackoverflow.com/questions/2013181/gdb-causes-sem-wait-to-fail-with-eintr-error int rc; do { rc = sem_wait(&m_sema); } while (rc == -1 && errno == EINTR); } bool try_wait() { int rc; do { rc = sem_trywait(&m_sema); } while (rc == -1 && errno == EINTR); return !(rc == -1 && errno == EAGAIN); } bool timed_wait(std::uint64_t usecs) { struct timespec ts; const int usecs_in_1_sec = 1000000; const int nsecs_in_1_sec = 1000000000; clock_gettime(CLOCK_REALTIME, &ts); ts.tv_sec += usecs / usecs_in_1_sec; ts.tv_nsec += (usecs % usecs_in_1_sec) * 1000; // sem_timedwait bombs if you have more than 1e9 in tv_nsec // so we have to clean things up before passing it in if (ts.tv_nsec > nsecs_in_1_sec) { ts.tv_nsec -= nsecs_in_1_sec; ++ts.tv_sec; } int rc; do { rc = sem_timedwait(&m_sema, &ts); } while (rc == -1 && errno == EINTR); return !(rc == -1 && errno == ETIMEDOUT); } void signal() { sem_post(&m_sema); } void signal(int count) { while (count-- > 0) { sem_post(&m_sema); } } }; #else #error Unsupported platform! (No semaphore wrapper available) #endif //--------------------------------------------------------- // LightweightSemaphore //--------------------------------------------------------- class LightweightSemaphore { public: typedef std::make_signed::type ssize_t; private: std::atomic m_count; Semaphore m_sema; bool waitWithPartialSpinning(std::int64_t timeout_usecs = -1) { ssize_t oldCount; // Is there a better way to set the initial spin count? // If we lower it to 1000, testBenaphore becomes 15x slower on my Core i7-5930K Windows PC, // as threads start hitting the kernel semaphore. int spin = 10000; while (--spin >= 0) { oldCount = m_count.load(std::memory_order_relaxed); if ((oldCount > 0) && m_count.compare_exchange_strong(oldCount, oldCount - 1, std::memory_order_acquire, std::memory_order_relaxed)) return true; std::atomic_signal_fence(std::memory_order_acquire); // Prevent the compiler from collapsing the loop. } oldCount = m_count.fetch_sub(1, std::memory_order_acquire); if (oldCount > 0) return true; if (timeout_usecs < 0) { m_sema.wait(); return true; } if (m_sema.timed_wait((std::uint64_t)timeout_usecs)) return true; // At this point, we've timed out waiting for the semaphore, but the // count is still decremented indicating we may still be waiting on // it. So we have to re-adjust the count, but only if the semaphore // wasn't signaled enough times for us too since then. If it was, we // need to release the semaphore too. while (true) { oldCount = m_count.load(std::memory_order_acquire); if (oldCount >= 0 && m_sema.try_wait()) return true; if (oldCount < 0 && m_count.compare_exchange_strong(oldCount, oldCount + 1, std::memory_order_relaxed)) return false; } } ssize_t waitManyWithPartialSpinning(ssize_t max, std::int64_t timeout_usecs = -1) { assert(max > 0); ssize_t oldCount; int spin = 10000; while (--spin >= 0) { oldCount = m_count.load(std::memory_order_relaxed); if (oldCount > 0) { ssize_t newCount = oldCount > max ? oldCount - max : 0; if (m_count.compare_exchange_strong(oldCount, newCount, std::memory_order_acquire, std::memory_order_relaxed)) return oldCount - newCount; } std::atomic_signal_fence(std::memory_order_acquire); } oldCount = m_count.fetch_sub(1, std::memory_order_acquire); if (oldCount <= 0) { if (timeout_usecs < 0) m_sema.wait(); else if (!m_sema.timed_wait((std::uint64_t)timeout_usecs)) { while (true) { oldCount = m_count.load(std::memory_order_acquire); if (oldCount >= 0 && m_sema.try_wait()) break; if (oldCount < 0 && m_count.compare_exchange_strong(oldCount, oldCount + 1, std::memory_order_relaxed)) return 0; } } } if (max > 1) return 1 + tryWaitMany(max - 1); return 1; } public: LightweightSemaphore(ssize_t initialCount = 0) : m_count(initialCount) { assert(initialCount >= 0); } bool tryWait() { ssize_t oldCount = m_count.load(std::memory_order_relaxed); while (oldCount > 0) { if (m_count.compare_exchange_weak(oldCount, oldCount - 1, std::memory_order_acquire, std::memory_order_relaxed)) return true; } return false; } void wait() { if (!tryWait()) waitWithPartialSpinning(); } bool wait(std::int64_t timeout_usecs) { return tryWait() || waitWithPartialSpinning(timeout_usecs); } // Acquires between 0 and (greedily) max, inclusive ssize_t tryWaitMany(ssize_t max) { assert(max >= 0); ssize_t oldCount = m_count.load(std::memory_order_relaxed); while (oldCount > 0) { ssize_t newCount = oldCount > max ? oldCount - max : 0; if (m_count.compare_exchange_weak(oldCount, newCount, std::memory_order_acquire, std::memory_order_relaxed)) return oldCount - newCount; } return 0; } // Acquires at least one, and (greedily) at most max ssize_t waitMany(ssize_t max, std::int64_t timeout_usecs) { assert(max >= 0); ssize_t result = tryWaitMany(max); if (result == 0 && max > 0) result = waitManyWithPartialSpinning(max, timeout_usecs); return result; } ssize_t waitMany(ssize_t max) { ssize_t result = waitMany(max, -1); assert(result > 0); return result; } void signal(ssize_t count = 1) { assert(count >= 0); ssize_t oldCount = m_count.fetch_add(count, std::memory_order_release); ssize_t toRelease = -oldCount < count ? -oldCount : count; if (toRelease > 0) { m_sema.signal((int)toRelease); } } ssize_t availableApprox() const { ssize_t count = m_count.load(std::memory_order_relaxed); return count > 0 ? count : 0; } }; } // end namespace mpmc_sema } // end namespace details // 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 class BlockingConcurrentQueue { private: typedef ::moodycamel::ConcurrentQueue ConcurrentQueue; typedef details::mpmc_sema::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::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(), &BlockingConcurrentQueue::template destroy) { assert(reinterpret_cast((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(), &BlockingConcurrentQueue::template destroy) { assert(reinterpret_cast((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 inline bool enqueue_bulk(It itemFirst, size_t count) { if (details::likely(inner.enqueue_bulk(std::forward(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 inline bool enqueue_bulk(producer_token_t const& token, It itemFirst, size_t count) { if (details::likely(inner.enqueue_bulk(token, std::forward(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 inline bool try_enqueue_bulk(It itemFirst, size_t count) { if (inner.try_enqueue_bulk(std::forward(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 inline bool try_enqueue_bulk(producer_token_t const& token, It itemFirst, size_t count) { if (inner.try_enqueue_bulk(token, std::forward(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 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 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 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(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 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(token, itemFirst, max - count); } return count; } // Blocks the current thread until there's something to dequeue, then // dequeues it. // Never allocates. Thread-safe. template inline void wait_dequeue(U& item) { sema->wait(); 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 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 inline bool wait_dequeue_timed(U& item, std::chrono::duration const& timeout) { return wait_dequeue_timed(item, std::chrono::duration_cast(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 inline void wait_dequeue(consumer_token_t& token, U& item) { sema->wait(); 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 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 inline bool wait_dequeue_timed(consumer_token_t& token, U& item, std::chrono::duration const& timeout) { return wait_dequeue_timed(token, item, std::chrono::duration_cast(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 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(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 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(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 inline size_t wait_dequeue_bulk_timed(It itemFirst, size_t max, std::chrono::duration const& timeout) { return wait_dequeue_bulk_timed(itemFirst, max, std::chrono::duration_cast(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 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(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 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(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 inline size_t wait_dequeue_bulk_timed(consumer_token_t& token, It itemFirst, size_t max, std::chrono::duration const& timeout) { return wait_dequeue_bulk_timed(token, itemFirst, max, std::chrono::duration_cast(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 bool is_lock_free() { return ConcurrentQueue::is_lock_free(); } private: template static inline U* create() { auto p = (Traits::malloc)(sizeof(U)); return p != nullptr ? new (p) U : nullptr; } template static inline U* create(A1&& a1) { auto p = (Traits::malloc)(sizeof(U)); return p != nullptr ? new (p) U(std::forward(a1)) : nullptr; } template static inline void destroy(U* p) { if (p != nullptr) { p->~U(); } (Traits::free)(p); } private: ConcurrentQueue inner; std::unique_ptr sema; }; template inline void swap(BlockingConcurrentQueue& a, BlockingConcurrentQueue& b) MOODYCAMEL_NOEXCEPT { a.swap(b); } } // end namespace moodycamel