1 files changed, 940 insertions, 0 deletions

diff --git a/src/common/reader_writer_queue.h b/src/common/reader_writer_queue.h
new file mode 100644
index 000000000..60c41a8cb
--- /dev/null
+++ b/src/common/reader_writer_queue.h
@@ -0,0 +1,940 @@
+// SPDX-FileCopyrightText: 2013-2020 Cameron Desrochers
+// SPDX-License-Identifier: BSD-2-Clause
+
+#pragma once
+
+#include <cassert>
+#include <cstdint>
+#include <cstdlib> // For malloc/free/abort & size_t
+#include <memory>
+#include <new>
+#include <stdexcept>
+#include <type_traits>
+#include <utility>
+
+#include "common/atomic_helpers.h"
+
+#if __cplusplus > 199711L || _MSC_VER >= 1700 // C++11 or VS2012
+#include <chrono>
+#endif
+
+// A lock-free queue for a single-consumer, single-producer architecture.
+// The queue is also wait-free in the common path (except if more memory
+// needs to be allocated, in which case malloc is called).
+// Allocates memory sparingly, and only once if the original maximum size
+// estimate is never exceeded.
+// Tested on x86/x64 processors, but semantics should be correct for all
+// architectures (given the right implementations in atomicops.h), provided
+// that aligned integer and pointer accesses are naturally atomic.
+// Note that there should only be one consumer thread and producer thread;
+// Switching roles of the threads, or using multiple consecutive threads for
+// one role, is not safe unless properly synchronized.
+// Using the queue exclusively from one thread is fine, though a bit silly.
+
+#ifndef MOODYCAMEL_CACHE_LINE_SIZE
+#define MOODYCAMEL_CACHE_LINE_SIZE 64
+#endif
+
+#ifndef MOODYCAMEL_EXCEPTIONS_ENABLED
+#if (defined(_MSC_VER) && defined(_CPPUNWIND)) || (defined(__GNUC__) && defined(__EXCEPTIONS)) ||  \
+    (!defined(_MSC_VER) && !defined(__GNUC__))
+#define MOODYCAMEL_EXCEPTIONS_ENABLED
+#endif
+#endif
+
+#ifndef MOODYCAMEL_HAS_EMPLACE
+#if !defined(_MSC_VER) ||                                                                          \
+    _MSC_VER >= 1800 // variadic templates: either a non-MS compiler or VS >= 2013
+#define MOODYCAMEL_HAS_EMPLACE 1
+#endif
+#endif
+
+#ifndef MOODYCAMEL_MAYBE_ALIGN_TO_CACHELINE
+#if defined(__APPLE__) && defined(__MACH__) && __cplusplus >= 201703L
+// This is required to find out what deployment target we are using
+#include <CoreFoundation/CoreFoundation.h>
+#if !defined(MAC_OS_X_VERSION_MIN_REQUIRED) ||                                                     \
+    MAC_OS_X_VERSION_MIN_REQUIRED < MAC_OS_X_VERSION_10_14
+// C++17 new(size_t, align_val_t) is not backwards-compatible with older versions of macOS, so we
+// can't support over-alignment in this case
+#define MOODYCAMEL_MAYBE_ALIGN_TO_CACHELINE
+#endif
+#endif
+#endif
+
+#ifndef MOODYCAMEL_MAYBE_ALIGN_TO_CACHELINE
+#define MOODYCAMEL_MAYBE_ALIGN_TO_CACHELINE AE_ALIGN(MOODYCAMEL_CACHE_LINE_SIZE)
+#endif
+
+#ifdef AE_VCPP
+#pragma warning(push)
+#pragma warning(disable : 4324) // structure was padded due to __declspec(align())
+#pragma warning(disable : 4820) // padding was added
+#pragma warning(disable : 4127) // conditional expression is constant
+#endif
+
+namespace Common {
+
+template <typename T, size_t MAX_BLOCK_SIZE = 512>
+class MOODYCAMEL_MAYBE_ALIGN_TO_CACHELINE ReaderWriterQueue {
+    // Design: Based on a queue-of-queues. The low-level queues are just
+    // circular buffers with front and tail indices indicating where the
+    // next element to dequeue is and where the next element can be enqueued,
+    // respectively. Each low-level queue is called a "block". Each block
+    // wastes exactly one element's worth of space to keep the design simple
+    // (if front == tail then the queue is empty, and can't be full).
+    // The high-level queue is a circular linked list of blocks; again there
+    // is a front and tail, but this time they are pointers to the blocks.
+    // The front block is where the next element to be dequeued is, provided
+    // the block is not empty. The back block is where elements are to be
+    // enqueued, provided the block is not full.
+    // The producer thread owns all the tail indices/pointers. The consumer
+    // thread owns all the front indices/pointers. Both threads read each
+    // other's variables, but only the owning thread updates them. E.g. After
+    // the consumer reads the producer's tail, the tail may change before the
+    // consumer is done dequeuing an object, but the consumer knows the tail
+    // will never go backwards, only forwards.
+    // If there is no room to enqueue an object, an additional block (of
+    // equal size to the last block) is added. Blocks are never removed.
+
+public:
+    typedef T value_type;
+
+    // Constructs a queue that can hold at least `size` elements without further
+    // allocations. If more than MAX_BLOCK_SIZE elements are requested,
+    // then several blocks of MAX_BLOCK_SIZE each are reserved (including
+    // at least one extra buffer block).
+    AE_NO_TSAN explicit ReaderWriterQueue(size_t size = 15)
+#ifndef NDEBUG
+        : enqueuing(false), dequeuing(false)
+#endif
+    {
+        assert(MAX_BLOCK_SIZE == ceilToPow2(MAX_BLOCK_SIZE) &&
+               "MAX_BLOCK_SIZE must be a power of 2");
+        assert(MAX_BLOCK_SIZE >= 2 && "MAX_BLOCK_SIZE must be at least 2");
+
+        Block* firstBlock = nullptr;
+
+        largestBlockSize =
+            ceilToPow2(size + 1); // We need a spare slot to fit size elements in the block
+        if (largestBlockSize > MAX_BLOCK_SIZE * 2) {
+            // We need a spare block in case the producer is writing to a different block the
+            // consumer is reading from, and wants to enqueue the maximum number of elements. We
+            // also need a spare element in each block to avoid the ambiguity between front == tail
+            // meaning "empty" and "full". So the effective number of slots that are guaranteed to
+            // be usable at any time is the block size - 1 times the number of blocks - 1. Solving
+            // for size and applying a ceiling to the division gives us (after simplifying):
+            size_t initialBlockCount = (size + MAX_BLOCK_SIZE * 2 - 3) / (MAX_BLOCK_SIZE - 1);
+            largestBlockSize = MAX_BLOCK_SIZE;
+            Block* lastBlock = nullptr;
+            for (size_t i = 0; i != initialBlockCount; ++i) {
+                auto block = make_block(largestBlockSize);
+                if (block == nullptr) {
+#ifdef MOODYCAMEL_EXCEPTIONS_ENABLED
+                    throw std::bad_alloc();
+#else
+                    abort();
+#endif
+                }
+                if (firstBlock == nullptr) {
+                    firstBlock = block;
+                } else {
+                    lastBlock->next = block;
+                }
+                lastBlock = block;
+                block->next = firstBlock;
+            }
+        } else {
+            firstBlock = make_block(largestBlockSize);
+            if (firstBlock == nullptr) {
+#ifdef MOODYCAMEL_EXCEPTIONS_ENABLED
+                throw std::bad_alloc();
+#else
+                abort();
+#endif
+            }
+            firstBlock->next = firstBlock;
+        }
+        frontBlock = firstBlock;
+        tailBlock = firstBlock;
+
+        // Make sure the reader/writer threads will have the initialized memory setup above:
+        fence(memory_order_sync);
+    }
+
+    // Note: The queue should not be accessed concurrently while it's
+    // being moved. It's up to the user to synchronize this.
+    AE_NO_TSAN ReaderWriterQueue(ReaderWriterQueue&& other)
+        : frontBlock(other.frontBlock.load()), tailBlock(other.tailBlock.load()),
+          largestBlockSize(other.largestBlockSize)
+#ifndef NDEBUG
+          ,
+          enqueuing(false), dequeuing(false)
+#endif
+    {
+        other.largestBlockSize = 32;
+        Block* b = other.make_block(other.largestBlockSize);
+        if (b == nullptr) {
+#ifdef MOODYCAMEL_EXCEPTIONS_ENABLED
+            throw std::bad_alloc();
+#else
+            abort();
+#endif
+        }
+        b->next = b;
+        other.frontBlock = b;
+        other.tailBlock = b;
+    }
+
+    // Note: The queue should not be accessed concurrently while it's
+    // being moved. It's up to the user to synchronize this.
+    ReaderWriterQueue& operator=(ReaderWriterQueue&& other) AE_NO_TSAN {
+        Block* b = frontBlock.load();
+        frontBlock = other.frontBlock.load();
+        other.frontBlock = b;
+        b = tailBlock.load();
+        tailBlock = other.tailBlock.load();
+        other.tailBlock = b;
+        std::swap(largestBlockSize, other.largestBlockSize);
+        return *this;
+    }
+
+    // Note: The queue should not be accessed concurrently while it's
+    // being deleted. It's up to the user to synchronize this.
+    AE_NO_TSAN ~ReaderWriterQueue() {
+        // Make sure we get the latest version of all variables from other CPUs:
+        fence(memory_order_sync);
+
+        // Destroy any remaining objects in queue and free memory
+        Block* frontBlock_ = frontBlock;
+        Block* block = frontBlock_;
+        do {
+            Block* nextBlock = block->next;
+            size_t blockFront = block->front;
+            size_t blockTail = block->tail;
+
+            for (size_t i = blockFront; i != blockTail; i = (i + 1) & block->sizeMask) {
+                auto element = reinterpret_cast<T*>(block->data + i * sizeof(T));
+                element->~T();
+                (void)element;
+            }
+
+            auto rawBlock = block->rawThis;
+            block->~Block();
+            std::free(rawBlock);
+            block = nextBlock;
+        } while (block != frontBlock_);
+    }
+
+    // Enqueues a copy of element if there is room in the queue.
+    // Returns true if the element was enqueued, false otherwise.
+    // Does not allocate memory.
+    AE_FORCEINLINE bool try_enqueue(T const& element) AE_NO_TSAN {
+        return inner_enqueue<CannotAlloc>(element);
+    }
+
+    // Enqueues a moved copy of element if there is room in the queue.
+    // Returns true if the element was enqueued, false otherwise.
+    // Does not allocate memory.
+    AE_FORCEINLINE bool try_enqueue(T&& element) AE_NO_TSAN {
+        return inner_enqueue<CannotAlloc>(std::forward<T>(element));
+    }
+
+#if MOODYCAMEL_HAS_EMPLACE
+    // Like try_enqueue() but with emplace semantics (i.e. construct-in-place).
+    template <typename... Args>
+    AE_FORCEINLINE bool try_emplace(Args&&... args) AE_NO_TSAN {
+        return inner_enqueue<CannotAlloc>(std::forward<Args>(args)...);
+    }
+#endif
+
+    // Enqueues a copy of element on the queue.
+    // Allocates an additional block of memory if needed.
+    // Only fails (returns false) if memory allocation fails.
+    AE_FORCEINLINE bool enqueue(T const& element) AE_NO_TSAN {
+        return inner_enqueue<CanAlloc>(element);
+    }
+
+    // Enqueues a moved copy of element on the queue.
+    // Allocates an additional block of memory if needed.
+    // Only fails (returns false) if memory allocation fails.
+    AE_FORCEINLINE bool enqueue(T&& element) AE_NO_TSAN {
+        return inner_enqueue<CanAlloc>(std::forward<T>(element));
+    }
+
+#if MOODYCAMEL_HAS_EMPLACE
+    // Like enqueue() but with emplace semantics (i.e. construct-in-place).
+    template <typename... Args>
+    AE_FORCEINLINE bool emplace(Args&&... args) AE_NO_TSAN {
+        return inner_enqueue<CanAlloc>(std::forward<Args>(args)...);
+    }
+#endif
+
+    // Attempts to dequeue an element; if the queue is empty,
+    // returns false instead. If the queue has at least one element,
+    // moves front to result using operator=, then returns true.
+    template <typename U>
+    bool try_dequeue(U& result) AE_NO_TSAN {
+#ifndef NDEBUG
+        ReentrantGuard guard(this->dequeuing);
+#endif
+
+        // High-level pseudocode:
+        // Remember where the tail block is
+        // If the front block has an element in it, dequeue it
+        // Else
+        //     If front block was the tail block when we entered the function, return false
+        //     Else advance to next block and dequeue the item there
+
+        // Note that we have to use the value of the tail block from before we check if the front
+        // block is full or not, in case the front block is empty and then, before we check if the
+        // tail block is at the front block or not, the producer fills up the front block *and
+        // moves on*, which would make us skip a filled block. Seems unlikely, but was consistently
+        // reproducible in practice.
+        // In order to avoid overhead in the common case, though, we do a double-checked pattern
+        // where we have the fast path if the front block is not empty, then read the tail block,
+        // then re-read the front block and check if it's not empty again, then check if the tail
+        // block has advanced.
+
+        Block* frontBlock_ = frontBlock.load();
+        size_t blockTail = frontBlock_->localTail;
+        size_t blockFront = frontBlock_->front.load();
+
+        if (blockFront != blockTail ||
+            blockFront != (frontBlock_->localTail = frontBlock_->tail.load())) {
+            fence(memory_order_acquire);
+
+        non_empty_front_block:
+            // Front block not empty, dequeue from here
+            auto element = reinterpret_cast<T*>(frontBlock_->data + blockFront * sizeof(T));
+            result = std::move(*element);
+            element->~T();
+
+            blockFront = (blockFront + 1) & frontBlock_->sizeMask;
+
+            fence(memory_order_release);
+            frontBlock_->front = blockFront;
+        } else if (frontBlock_ != tailBlock.load()) {
+            fence(memory_order_acquire);
+
+            frontBlock_ = frontBlock.load();
+            blockTail = frontBlock_->localTail = frontBlock_->tail.load();
+            blockFront = frontBlock_->front.load();
+            fence(memory_order_acquire);
+
+            if (blockFront != blockTail) {
+                // Oh look, the front block isn't empty after all
+                goto non_empty_front_block;
+            }
+
+            // Front block is empty but there's another block ahead, advance to it
+            Block* nextBlock = frontBlock_->next;
+            // Don't need an acquire fence here since next can only ever be set on the tailBlock,
+            // and we're not the tailBlock, and we did an acquire earlier after reading tailBlock
+            // which ensures next is up-to-date on this CPU in case we recently were at tailBlock.
+
+            size_t nextBlockFront = nextBlock->front.load();
+            size_t nextBlockTail = nextBlock->localTail = nextBlock->tail.load();
+            fence(memory_order_acquire);
+
+            // Since the tailBlock is only ever advanced after being written to,
+            // we know there's for sure an element to dequeue on it
+            assert(nextBlockFront != nextBlockTail);
+            AE_UNUSED(nextBlockTail);
+
+            // We're done with this block, let the producer use it if it needs
+            fence(memory_order_release); // Expose possibly pending changes to frontBlock->front
+                                         // from last dequeue
+            frontBlock = frontBlock_ = nextBlock;
+
+            compiler_fence(memory_order_release); // Not strictly needed
+
+            auto element = reinterpret_cast<T*>(frontBlock_->data + nextBlockFront * sizeof(T));
+
+            result = std::move(*element);
+            element->~T();
+
+            nextBlockFront = (nextBlockFront + 1) & frontBlock_->sizeMask;
+
+            fence(memory_order_release);
+            frontBlock_->front = nextBlockFront;
+        } else {
+            // No elements in current block and no other block to advance to
+            return false;
+        }
+
+        return true;
+    }
+
+    // Returns a pointer to the front element in the queue (the one that
+    // would be removed next by a call to `try_dequeue` or `pop`). If the
+    // queue appears empty at the time the method is called, nullptr is
+    // returned instead.
+    // Must be called only from the consumer thread.
+    T* peek() const AE_NO_TSAN {
+#ifndef NDEBUG
+        ReentrantGuard guard(this->dequeuing);
+#endif
+        // See try_dequeue() for reasoning
+
+        Block* frontBlock_ = frontBlock.load();
+        size_t blockTail = frontBlock_->localTail;
+        size_t blockFront = frontBlock_->front.load();
+
+        if (blockFront != blockTail ||
+            blockFront != (frontBlock_->localTail = frontBlock_->tail.load())) {
+            fence(memory_order_acquire);
+        non_empty_front_block:
+            return reinterpret_cast<T*>(frontBlock_->data + blockFront * sizeof(T));
+        } else if (frontBlock_ != tailBlock.load()) {
+            fence(memory_order_acquire);
+            frontBlock_ = frontBlock.load();
+            blockTail = frontBlock_->localTail = frontBlock_->tail.load();
+            blockFront = frontBlock_->front.load();
+            fence(memory_order_acquire);
+
+            if (blockFront != blockTail) {
+                goto non_empty_front_block;
+            }
+
+            Block* nextBlock = frontBlock_->next;
+
+            size_t nextBlockFront = nextBlock->front.load();
+            fence(memory_order_acquire);
+
+            assert(nextBlockFront != nextBlock->tail.load());
+            return reinterpret_cast<T*>(nextBlock->data + nextBlockFront * sizeof(T));
+        }
+
+        return nullptr;
+    }
+
+    // Removes the front element from the queue, if any, without returning it.
+    // Returns true on success, or false if the queue appeared empty at the time
+    // `pop` was called.
+    bool pop() AE_NO_TSAN {
+#ifndef NDEBUG
+        ReentrantGuard guard(this->dequeuing);
+#endif
+        // See try_dequeue() for reasoning
+
+        Block* frontBlock_ = frontBlock.load();
+        size_t blockTail = frontBlock_->localTail;
+        size_t blockFront = frontBlock_->front.load();
+
+        if (blockFront != blockTail ||
+            blockFront != (frontBlock_->localTail = frontBlock_->tail.load())) {
+            fence(memory_order_acquire);
+
+        non_empty_front_block:
+            auto element = reinterpret_cast<T*>(frontBlock_->data + blockFront * sizeof(T));
+            element->~T();
+
+            blockFront = (blockFront + 1) & frontBlock_->sizeMask;
+
+            fence(memory_order_release);
+            frontBlock_->front = blockFront;
+        } else if (frontBlock_ != tailBlock.load()) {
+            fence(memory_order_acquire);
+            frontBlock_ = frontBlock.load();
+            blockTail = frontBlock_->localTail = frontBlock_->tail.load();
+            blockFront = frontBlock_->front.load();
+            fence(memory_order_acquire);
+
+            if (blockFront != blockTail) {
+                goto non_empty_front_block;
+            }
+
+            // Front block is empty but there's another block ahead, advance to it
+            Block* nextBlock = frontBlock_->next;
+
+            size_t nextBlockFront = nextBlock->front.load();
+            size_t nextBlockTail = nextBlock->localTail = nextBlock->tail.load();
+            fence(memory_order_acquire);
+
+            assert(nextBlockFront != nextBlockTail);
+            AE_UNUSED(nextBlockTail);
+
+            fence(memory_order_release);
+            frontBlock = frontBlock_ = nextBlock;
+
+            compiler_fence(memory_order_release);
+
+            auto element = reinterpret_cast<T*>(frontBlock_->data + nextBlockFront * sizeof(T));
+            element->~T();
+
+            nextBlockFront = (nextBlockFront + 1) & frontBlock_->sizeMask;
+
+            fence(memory_order_release);
+            frontBlock_->front = nextBlockFront;
+        } else {
+            // No elements in current block and no other block to advance to
+            return false;
+        }
+
+        return true;
+    }
+
+    // Returns the approximate number of items currently in the queue.
+    // Safe to call from both the producer and consumer threads.
+    inline size_t size_approx() const AE_NO_TSAN {
+        size_t result = 0;
+        Block* frontBlock_ = frontBlock.load();
+        Block* block = frontBlock_;
+        do {
+            fence(memory_order_acquire);
+            size_t blockFront = block->front.load();
+            size_t blockTail = block->tail.load();
+            result += (blockTail - blockFront) & block->sizeMask;
+            block = block->next.load();
+        } while (block != frontBlock_);
+        return result;
+    }
+
+    // Returns the total number of items that could be enqueued without incurring
+    // an allocation when this queue is empty.
+    // Safe to call from both the producer and consumer threads.
+    //
+    // NOTE: The actual capacity during usage may be different depending on the consumer.
+    //       If the consumer is removing elements concurrently, the producer cannot add to
+    //       the block the consumer is removing from until it's completely empty, except in
+    //       the case where the producer was writing to the same block the consumer was
+    //       reading from the whole time.
+    inline size_t max_capacity() const {
+        size_t result = 0;
+        Block* frontBlock_ = frontBlock.load();
+        Block* block = frontBlock_;
+        do {
+            fence(memory_order_acquire);
+            result += block->sizeMask;
+            block = block->next.load();
+        } while (block != frontBlock_);
+        return result;
+    }
+
+private:
+    enum AllocationMode { CanAlloc, CannotAlloc };
+
+#if MOODYCAMEL_HAS_EMPLACE
+    template <AllocationMode canAlloc, typename... Args>
+    bool inner_enqueue(Args&&... args) AE_NO_TSAN
+#else
+    template <AllocationMode canAlloc, typename U>
+    bool inner_enqueue(U&& element) AE_NO_TSAN
+#endif
+    {
+#ifndef NDEBUG
+        ReentrantGuard guard(this->enqueuing);
+#endif
+
+        // High-level pseudocode (assuming we're allowed to alloc a new block):
+        // If room in tail block, add to tail
+        // Else check next block
+        //     If next block is not the head block, enqueue on next block
+        //     Else create a new block and enqueue there
+        //     Advance tail to the block we just enqueued to
+
+        Block* tailBlock_ = tailBlock.load();
+        size_t blockFront = tailBlock_->localFront;
+        size_t blockTail = tailBlock_->tail.load();
+
+        size_t nextBlockTail = (blockTail + 1) & tailBlock_->sizeMask;
+        if (nextBlockTail != blockFront ||
+            nextBlockTail != (tailBlock_->localFront = tailBlock_->front.load())) {
+            fence(memory_order_acquire);
+            // This block has room for at least one more element
+            char* location = tailBlock_->data + blockTail * sizeof(T);
+#if MOODYCAMEL_HAS_EMPLACE
+            new (location) T(std::forward<Args>(args)...);
+#else
+            new (location) T(std::forward<U>(element));
+#endif
+
+            fence(memory_order_release);
+            tailBlock_->tail = nextBlockTail;
+        } else {
+            fence(memory_order_acquire);
+            if (tailBlock_->next.load() != frontBlock) {
+                // Note that the reason we can't advance to the frontBlock and start adding new
+                // entries there is because if we did, then dequeue would stay in that block,
+                // eventually reading the new values, instead of advancing to the next full block
+                // (whose values were enqueued first and so should be consumed first).
+
+                fence(memory_order_acquire); // Ensure we get latest writes if we got the latest
+                                             // frontBlock
+
+                // tailBlock is full, but there's a free block ahead, use it
+                Block* tailBlockNext = tailBlock_->next.load();
+                size_t nextBlockFront = tailBlockNext->localFront = tailBlockNext->front.load();
+                nextBlockTail = tailBlockNext->tail.load();
+                fence(memory_order_acquire);
+
+                // This block must be empty since it's not the head block and we
+                // go through the blocks in a circle
+                assert(nextBlockFront == nextBlockTail);
+                tailBlockNext->localFront = nextBlockFront;
+
+                char* location = tailBlockNext->data + nextBlockTail * sizeof(T);
+#if MOODYCAMEL_HAS_EMPLACE
+                new (location) T(std::forward<Args>(args)...);
+#else
+                new (location) T(std::forward<U>(element));
+#endif
+
+                tailBlockNext->tail = (nextBlockTail + 1) & tailBlockNext->sizeMask;
+
+                fence(memory_order_release);
+                tailBlock = tailBlockNext;
+            } else if (canAlloc == CanAlloc) {
+                // tailBlock is full and there's no free block ahead; create a new block
+                auto newBlockSize =
+                    largestBlockSize >= MAX_BLOCK_SIZE ? largestBlockSize : largestBlockSize * 2;
+                auto newBlock = make_block(newBlockSize);
+                if (newBlock == nullptr) {
+                    // Could not allocate a block!
+                    return false;
+                }
+                largestBlockSize = newBlockSize;
+
+#if MOODYCAMEL_HAS_EMPLACE
+                new (newBlock->data) T(std::forward<Args>(args)...);
+#else
+                new (newBlock->data) T(std::forward<U>(element));
+#endif
+                assert(newBlock->front == 0);
+                newBlock->tail = newBlock->localTail = 1;
+
+                newBlock->next = tailBlock_->next.load();
+                tailBlock_->next = newBlock;
+
+                // Might be possible for the dequeue thread to see the new tailBlock->next
+                // *without* seeing the new tailBlock value, but this is OK since it can't
+                // advance to the next block until tailBlock is set anyway (because the only
+                // case where it could try to read the next is if it's already at the tailBlock,
+                // and it won't advance past tailBlock in any circumstance).
+
+                fence(memory_order_release);
+                tailBlock = newBlock;
+            } else if (canAlloc == CannotAlloc) {
+                // Would have had to allocate a new block to enqueue, but not allowed
+                return false;
+            } else {
+                assert(false && "Should be unreachable code");
+                return false;
+            }
+        }
+
+        return true;
+    }
+
+    // Disable copying
+    ReaderWriterQueue(ReaderWriterQueue const&) {}
+
+    // Disable assignment
+    ReaderWriterQueue& operator=(ReaderWriterQueue const&) {}
+
+    AE_FORCEINLINE static size_t ceilToPow2(size_t x) {
+        // From http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
+        --x;
+        x |= x >> 1;
+        x |= x >> 2;
+        x |= x >> 4;
+        for (size_t i = 1; i < sizeof(size_t); i <<= 1) {
+            x |= x >> (i << 3);
+        }
+        ++x;
+        return x;
+    }
+
+    template <typename U>
+    static AE_FORCEINLINE char* align_for(char* ptr) AE_NO_TSAN {
+        const std::size_t alignment = std::alignment_of<U>::value;
+        return ptr + (alignment - (reinterpret_cast<std::uintptr_t>(ptr) % alignment)) % alignment;
+    }
+
+private:
+#ifndef NDEBUG
+    struct ReentrantGuard {
+        AE_NO_TSAN ReentrantGuard(weak_atomic<bool>& _inSection) : inSection(_inSection) {
+            assert(!inSection &&
+                   "Concurrent (or re-entrant) enqueue or dequeue operation detected (only one "
+                   "thread at a time may hold the producer or consumer role)");
+            inSection = true;
+        }
+
+        AE_NO_TSAN ~ReentrantGuard() {
+            inSection = false;
+        }
+
+    private:
+        ReentrantGuard& operator=(ReentrantGuard const&);
+
+    private:
+        weak_atomic<bool>& inSection;
+    };
+#endif
+
+    struct Block {
+        // Avoid false-sharing by putting highly contended variables on their own cache lines
+        weak_atomic<size_t> front; // (Atomic) Elements are read from here
+        size_t localTail;          // An uncontended shadow copy of tail, owned by the consumer
+
+        char cachelineFiller0[MOODYCAMEL_CACHE_LINE_SIZE - sizeof(weak_atomic<size_t>) -
+                              sizeof(size_t)];
+        weak_atomic<size_t> tail; // (Atomic) Elements are enqueued here
+        size_t localFront;
+
+        char cachelineFiller1[MOODYCAMEL_CACHE_LINE_SIZE - sizeof(weak_atomic<size_t>) -
+                              sizeof(size_t)]; // next isn't very contended, but we don't want it on
+                                               // the same cache line as tail (which is)
+        weak_atomic<Block*> next;              // (Atomic)
+
+        char* data; // Contents (on heap) are aligned to T's alignment
+
+        const size_t sizeMask;
+
+        // size must be a power of two (and greater than 0)
+        AE_NO_TSAN Block(size_t const& _size, char* _rawThis, char* _data)
+            : front(0UL), localTail(0), tail(0UL), localFront(0), next(nullptr), data(_data),
+              sizeMask(_size - 1), rawThis(_rawThis) {}
+
+    private:
+        // C4512 - Assignment operator could not be generated
+        Block& operator=(Block const&);
+
+    public:
+        char* rawThis;
+    };
+
+    static Block* make_block(size_t capacity) AE_NO_TSAN {
+        // Allocate enough memory for the block itself, as well as all the elements it will contain
+        auto size = sizeof(Block) + std::alignment_of<Block>::value - 1;
+        size += sizeof(T) * capacity + std::alignment_of<T>::value - 1;
+        auto newBlockRaw = static_cast<char*>(std::malloc(size));
+        if (newBlockRaw == nullptr) {
+            return nullptr;
+        }
+
+        auto newBlockAligned = align_for<Block>(newBlockRaw);
+        auto newBlockData = align_for<T>(newBlockAligned + sizeof(Block));
+        return new (newBlockAligned) Block(capacity, newBlockRaw, newBlockData);
+    }
+
+private:
+    weak_atomic<Block*> frontBlock; // (Atomic) Elements are dequeued from this block
+
+    char cachelineFiller[MOODYCAMEL_CACHE_LINE_SIZE - sizeof(weak_atomic<Block*>)];
+    weak_atomic<Block*> tailBlock; // (Atomic) Elements are enqueued to this block
+
+    size_t largestBlockSize;
+
+#ifndef NDEBUG
+    weak_atomic<bool> enqueuing;
+    mutable weak_atomic<bool> dequeuing;
+#endif
+};
+
+// Like ReaderWriterQueue, but also providees blocking operations
+template <typename T, size_t MAX_BLOCK_SIZE = 512>
+class BlockingReaderWriterQueue {
+private:
+    typedef ::Common::ReaderWriterQueue<T, MAX_BLOCK_SIZE> ReaderWriterQueue;
+
+public:
+    explicit BlockingReaderWriterQueue(size_t size = 15) AE_NO_TSAN
+        : inner(size),
+          sema(new spsc_sema::LightweightSemaphore()) {}
+
+    BlockingReaderWriterQueue(BlockingReaderWriterQueue&& other) AE_NO_TSAN
+        : inner(std::move(other.inner)),
+          sema(std::move(other.sema)) {}
+
+    BlockingReaderWriterQueue& operator=(BlockingReaderWriterQueue&& other) AE_NO_TSAN {
+        std::swap(sema, other.sema);
+        std::swap(inner, other.inner);
+        return *this;
+    }
+
+    // Enqueues a copy of element if there is room in the queue.
+    // Returns true if the element was enqueued, false otherwise.
+    // Does not allocate memory.
+    AE_FORCEINLINE bool try_enqueue(T const& element) AE_NO_TSAN {
+        if (inner.try_enqueue(element)) {
+            sema->signal();
+            return true;
+        }
+        return false;
+    }
+
+    // Enqueues a moved copy of element if there is room in the queue.
+    // Returns true if the element was enqueued, false otherwise.
+    // Does not allocate memory.
+    AE_FORCEINLINE bool try_enqueue(T&& element) AE_NO_TSAN {
+        if (inner.try_enqueue(std::forward<T>(element))) {
+            sema->signal();
+            return true;
+        }
+        return false;
+    }
+
+#if MOODYCAMEL_HAS_EMPLACE
+    // Like try_enqueue() but with emplace semantics (i.e. construct-in-place).
+    template <typename... Args>
+    AE_FORCEINLINE bool try_emplace(Args&&... args) AE_NO_TSAN {
+        if (inner.try_emplace(std::forward<Args>(args)...)) {
+            sema->signal();
+            return true;
+        }
+        return false;
+    }
+#endif
+
+    // Enqueues a copy of element on the queue.
+    // Allocates an additional block of memory if needed.
+    // Only fails (returns false) if memory allocation fails.
+    AE_FORCEINLINE bool enqueue(T const& element) AE_NO_TSAN {
+        if (inner.enqueue(element)) {
+            sema->signal();
+            return true;
+        }
+        return false;
+    }
+
+    // Enqueues a moved copy of element on the queue.
+    // Allocates an additional block of memory if needed.
+    // Only fails (returns false) if memory allocation fails.
+    AE_FORCEINLINE bool enqueue(T&& element) AE_NO_TSAN {
+        if (inner.enqueue(std::forward<T>(element))) {
+            sema->signal();
+            return true;
+        }
+        return false;
+    }
+
+#if MOODYCAMEL_HAS_EMPLACE
+    // Like enqueue() but with emplace semantics (i.e. construct-in-place).
+    template <typename... Args>
+    AE_FORCEINLINE bool emplace(Args&&... args) AE_NO_TSAN {
+        if (inner.emplace(std::forward<Args>(args)...)) {
+            sema->signal();
+            return true;
+        }
+        return false;
+    }
+#endif
+
+    // Attempts to dequeue an element; if the queue is empty,
+    // returns false instead. If the queue has at least one element,
+    // moves front to result using operator=, then returns true.
+    template <typename U>
+    bool try_dequeue(U& result) AE_NO_TSAN {
+        if (sema->tryWait()) {
+            bool success = inner.try_dequeue(result);
+            assert(success);
+            AE_UNUSED(success);
+            return true;
+        }
+        return false;
+    }
+
+    // Attempts to dequeue an element; if the queue is empty,
+    // waits until an element is available, then dequeues it.
+    template <typename U>
+    void wait_dequeue(U& result) AE_NO_TSAN {
+        while (!sema->wait())
+            ;
+        bool success = inner.try_dequeue(result);
+        AE_UNUSED(result);
+        assert(success);
+        AE_UNUSED(success);
+    }
+
+    // Attempts to dequeue an element; if the queue is empty,
+    // waits until an element is available up to the specified timeout,
+    // then dequeues it and returns true, or returns false if the timeout
+    // expires before an element can be dequeued.
+    // Using a negative timeout indicates an indefinite timeout,
+    // and is thus functionally equivalent to calling wait_dequeue.
+    template <typename U>
+    bool wait_dequeue_timed(U& result, std::int64_t timeout_usecs) AE_NO_TSAN {
+        if (!sema->wait(timeout_usecs)) {
+            return false;
+        }
+        bool success = inner.try_dequeue(result);
+        AE_UNUSED(result);
+        assert(success);
+        AE_UNUSED(success);
+        return true;
+    }
+
+#if __cplusplus > 199711L || _MSC_VER >= 1700
+    // Attempts to dequeue an element; if the queue is empty,
+    // waits until an element is available up to the specified timeout,
+    // then dequeues it and returns true, or returns false if the timeout
+    // expires before an element can be dequeued.
+    // Using a negative timeout indicates an indefinite timeout,
+    // and is thus functionally equivalent to calling wait_dequeue.
+    template <typename U, typename Rep, typename Period>
+    inline bool wait_dequeue_timed(U& result,
+                                   std::chrono::duration<Rep, Period> const& timeout) AE_NO_TSAN {
+        return wait_dequeue_timed(
+            result, std::chrono::duration_cast<std::chrono::microseconds>(timeout).count());
+    }
+#endif
+
+    // Returns a pointer to the front element in the queue (the one that
+    // would be removed next by a call to `try_dequeue` or `pop`). If the
+    // queue appears empty at the time the method is called, nullptr is
+    // returned instead.
+    // Must be called only from the consumer thread.
+    AE_FORCEINLINE T* peek() const AE_NO_TSAN {
+        return inner.peek();
+    }
+
+    // Removes the front element from the queue, if any, without returning it.
+    // Returns true on success, or false if the queue appeared empty at the time
+    // `pop` was called.
+    AE_FORCEINLINE bool pop() AE_NO_TSAN {
+        if (sema->tryWait()) {
+            bool result = inner.pop();
+            assert(result);
+            AE_UNUSED(result);
+            return true;
+        }
+        return false;
+    }
+
+    // Returns the approximate number of items currently in the queue.
+    // Safe to call from both the producer and consumer threads.
+    AE_FORCEINLINE size_t size_approx() const AE_NO_TSAN {
+        return sema->availableApprox();
+    }
+
+    // Returns the total number of items that could be enqueued without incurring
+    // an allocation when this queue is empty.
+    // Safe to call from both the producer and consumer threads.
+    //
+    // NOTE: The actual capacity during usage may be different depending on the consumer.
+    //       If the consumer is removing elements concurrently, the producer cannot add to
+    //       the block the consumer is removing from until it's completely empty, except in
+    //       the case where the producer was writing to the same block the consumer was
+    //       reading from the whole time.
+    AE_FORCEINLINE size_t max_capacity() const {
+        return inner.max_capacity();
+    }
+
+private:
+    // Disable copying & assignment
+    BlockingReaderWriterQueue(BlockingReaderWriterQueue const&) {}
+    BlockingReaderWriterQueue& operator=(BlockingReaderWriterQueue const&) {}
+
+private:
+    ReaderWriterQueue inner;
+    std::unique_ptr<spsc_sema::LightweightSemaphore> sema;
+};
+
+} // namespace Common
+
+#ifdef AE_VCPP
+#pragma warning(pop)
+#endif