added README and LICENSE

LICENSE

@@ -0,0 +1,7 @@
+Copyright (c) 2026 Peisong Xiao
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the “Software”), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED “AS IS”, WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

README.md

@@ -0,0 +1,119 @@
+# ThreadWeaver - Lock-Free Multi-Thread Communication Templates
+A collection of lock-free intra-thread message-sending fabrics
+including SPSC, MPSC and SPMC templates, targeting x64 and ARMv8+
+platforms.
+
+The implementation avoids CAS retry loops and ensures a linearly
+bounded number of operations for fairness, leading to bounded latency
+for any request to be processed.  Fairness here means that no producer
+or consumer can be perpetually starved under continuous contention.
+
+Some variations of the same actions are provided for fine-tuning
+performance.
+
+## Table of Contents
+- [ThreadWeaver – Lock-Free Multi-Thread Communication Templates](#threadweaver---lock-free-multi-thread-communication-templates)
+- [Requirements](#requirements)
+- [Quick Start](#quick-start)
+  - [Explicitness](#explicitness)
+  - [Important Messages](#important-messages)
+  - [External Synchronization](#external-synchronization)
+  - [Variations](#variations)
+  - [Common Verbs](#common-verbs)
+    - [`[sync] init`](#sync-init)
+    - [`[sync] flush`](#sync-flush)
+    - [`send`](#send)
+    - [`recv`](#recv)
+- [Design and Inspiration](#design-and-inspiration)
+
+## Requirements
+The Weaver library requires a compiler supporting C++20 and above
+standards.
+
+## Quick Start
+Weaver is contained within one header in [weaver.h](include/weaver.h)
+to accommodate C++ specific template instantiation requirements.
+
+The user must provide the cache line size
+`--param=destructive-interference-size` or configure the static
+`THWeaver::CLS` parameter in order to compile with the library.  This
+is to ensure correct cache line isolation and avoid false sharing
+across platforms.
+
+**We will use the term "fabric" to refer to instantiated communication
+objects from the Weaver library.**
+
+The included classes are:
+1. SPSC: `THWeaver::EndpointQueue`
+2. MPSC: `THWeaver::FanInFabric`
+3. SPMC: `THWeaver::FanOutFabric`
+
+See [docs](docs/) for more detailed documentation on the classes and
+result enums.
+
+### Explicitness 
+The Weaver library expects that the user explicitly state the
+behavior for the fabric and does not rely on automatic constructors
+and destructors for state initialization and resource management.
+
+### Important Messages
+Throughout the documentation (including this README), all important
+messages will have a leading "IMPORTANT".
+
+Violations of important messages may result in **undefined behavior**.
+
+### External Synchronization
+Some non-critical Weaver methods may expect external synchronization,
+oriented towards control-plane usage rather than the actual data-plane
+pipelines.
+
+Use of these methods without synchronization may result in **undefined
+behaviors**.
+
+These operations are marked by `[sync]`.
+
+### Variations
+All class methods are named by `verb[_variation]`, and different
+variations of the same action may have different costs.
+
+This document will only contain an overview on the verb (action),
+please see [docs](docs/) for detailed views on variations
+
+### Common Verbs
+The verbs listed below are universal to all Weaver classes.
+
+#### `[sync] init`
+Explicitly initialize the fabric.
+
+**IMPORTANT: This method is expected to only be called once during
+the fabric's lifetime.**
+
+#### `[sync] flush`
+Reset the fabric or part of the fabric.
+
+#### `send`
+Moves a message into the fabric.  The return type will explicitly
+inform if and how it failed.
+
+#### `recv`
+Moves a message out of the fabric or initializes a token to the
+message.  The return type will explicitly inform if and how it failed.
+
+## Design and Inspiration
+Weaver is designed for the current generation and architecture of
+hardware and does not provide upwards compatibility to future
+hardware.  It assumes multi-level caching and high-cost of memory
+operations, and aims to reduce memory and cache coherence traffic by
+respecting the hardware cache architecture.
+
+And to ensure fairness for multiple producer or consumer threads,
+Weaver includes simple scheduling that degrades into round-robin
+schemes in the worst case.
+
+It is inspired by networking concepts and hardware clock domain
+crossing implementations.  And for each operation, it tries to keep
+modifications monotonic and data-flow unidirectional.
+
+Shared states that must be lossless are structured so that operations
+are causally ordered and monotonic, allowing simpler synchronization
+and reduced coherence traffic.

include/weaver.h

@@ -1,11 +1,36 @@
-#ifndef THWEAVER_FABRIC_H
-#define THWEAVER_FABRIC_H
+/*
+ * Copyright (c) 2026 Peisong Xiao
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ */
+
+#ifndef THREADWEAVER_WEAVER_H
+#define THREADWEAVER_WEAVER_H
 
 #include <array>
 #include <atomic>
+#include <bit>
 #include <cstddef>
 #include <cstdint>
+#include <limits>
 #include <new>
+#include <utility>
 
 namespace THWeaver {
 
@@ -23,44 +48,63 @@ enum class FanInFabricRecvTryResult { Ok, ErrTryFailed };
 
 enum class FanInFabricRecvAggrResult { Ok, ErrAggrFailed };
 
+template <typename BitmapType> struct FanOutFabricSendResult {
+        BitmapType failures;
+        enum { Ok, ErrPartialSuccess, ErrFullFailure } result;
+};
+
+enum class FanOutFabricRecvResult { Ok, ErrEmpty };
+
+enum class FanOutFabricDeallocResult { Ok, ErrReclaimQueueFull };
+
 template <typename MessageType, std::size_t qsize_expt> class EndpointQueue {
 public:
         static constexpr std::size_t QSIZE = 1 << qsize_expt;
         static constexpr std::size_t QSIZE_MASK = QSIZE - 1;
 
         EndpointQueue() noexcept {};
-        EndpointQueue(const EndpointQueue<MessageType, qsize_expt> &) = delete;
-        EndpointQueue &
-        operator=(const EndpointQueue<MessageType, qsize_expt> &) = delete;
-        EndpointQueue(EndpointQueue<MessageType, qsize_expt> &&) = delete;
-        EndpointQueue &
-        operator=(EndpointQueue<MessageType, qsize_expt> &&) = delete;
+        EndpointQueue(const EndpointQueue &) = delete;
+        EndpointQueue &operator=(const EndpointQueue &) = delete;
+        EndpointQueue(EndpointQueue &&) = delete;
+        EndpointQueue &operator=(EndpointQueue &&) = delete;
 
         void init() noexcept {
-                head.store(0);
-                tail.store(0);
+                head.store(0, std::memory_order_release);
+                tail.store(0, std::memory_order_release);
         }
 
         void flush() noexcept {
-                head.store(0);
-                tail.store(0);
+                head.store(0, std::memory_order_release);
+                tail.store(0, std::memory_order_release);
         }
 
-        std::size_t size() const noexcept {
-                return ((tail.load() + QSIZE_MASK) - head.load()) & QSIZE_MASK;
+        std::size_t get_size() const noexcept {
+                return ((tail.load(std::memory_order::acquire) + QSIZE_MASK) -
+                        head.load(std::memory_order::acquire)) &
+                       QSIZE_MASK;
         }
 
-        bool is_empty() const noexcept { return head.load() == tail.load(); }
+        bool is_empty() const noexcept {
+                return head.load(std::memory_order::acquire) ==
+                       tail.load(std::memory_order::acquire);
+        }
         bool is_full() const noexcept {
-                return head.load() == ((tail.load() + 1) & QSIZE_MASK);
+                return head.load(std::memory_order::acquire) ==
+                       ((tail.load(std::memory_order::acquire) + 1) &
+                        QSIZE_MASK);
         }
 
-        std::size_t get_head() const noexcept { return head.load(); }
-        std::size_t get_tail() const noexcept { return tail.load(); }
+        std::size_t get_head() const noexcept {
+                return head.load(std::memory_order::acquire);
+        }
+        std::size_t get_tail() const noexcept {
+                return tail.load(std::memory_order::acquire);
+        }
+        std::array<MessageType, QSIZE> &get_buffer() noexcept { return buffer; }
 
         EndpointQueueSendResult send(MessageType &&message) noexcept {
-                std::size_t h = head.load();
-                std::size_t t = tail.load();
+                std::size_t h = head.load(std::memory_order::acquire);
+                std::size_t t = tail.load(std::memory_order::acquire);
 
                 if (h == ((t + 1) & QSIZE_MASK))
                         return EndpointQueueSendResult::ErrFull;
@@ -68,14 +112,14 @@ public:
                 buffer[t] = std::move(message);
 
                 t = (t + 1) & QSIZE_MASK;
-                tail.store(t);
+                tail.store(t, std::memory_order_release);
 
                 return EndpointQueueSendResult::Ok;
         }
 
         EndpointQueueRecvResult recv(MessageType &buffer) noexcept {
-                std::size_t h = head.load();
-                std::size_t t = tail.load();
+                std::size_t h = head.load(std::memory_order::acquire);
+                std::size_t t = tail.load(std::memory_order::acquire);
 
                 if (h == t)
                         return EndpointQueueRecvResult::ErrEmpty;
@@ -83,15 +127,16 @@ public:
                 buffer = std::move(this->buffer[h]);
 
                 h = (h + 1) & QSIZE_MASK;
-                head.store(h);
+                head.store(h, std::memory_order_release);
 
                 return EndpointQueueRecvResult::Ok;
         }
 
-        void recv_unsafe(MessageType &buffer, std::size_t old_head) noexcept {
+        void recv_unsafe(MessageType &buffer, std::size_t &old_head) noexcept {
                 buffer = std::move(this->buffer[old_head]);
+                old_head = (old_head + 1) & QSIZE_MASK;
 
-                head.store((old_head + 1) & QSIZE_MASK);
+                head.store(old_head, std::memory_order_release);
         }
 
 private:
@@ -106,7 +151,7 @@ class FanInFabric {
 public:
         using BitmapType = uint64_t;
 
-        static constexpr std::size_t QSIZE = 1 << qsize_expt;
+        static constexpr std::size_t QSIZE = 1ULL << qsize_expt;
         static constexpr std::size_t QSIZE_MASK = QSIZE - 1;
         static constexpr std::size_t BITMAP_SIZE = sizeof(BitmapType) * 8;
         static constexpr BitmapType THREAD_BITMAP_MASK =
@@ -114,22 +159,16 @@ public:
                         ? ~BitmapType(0)
                         : (BitmapType(1) << IN_THREAD_CNT) - 1;
 
-        static_assert(IN_THREAD_CNT <= BITMAP_SIZE, "Producer limit exceeded");
+        static_assert(IN_THREAD_CNT <= BITMAP_SIZE, "Insufficient bitmap size");
 
         FanInFabric() noexcept {}
-        FanInFabric(const FanInFabric<MessageType, qsize_expt, IN_THREAD_CNT>
-                            &) = delete;
-        FanInFabric &
-        operator=(const FanInFabric<MessageType, qsize_expt, IN_THREAD_CNT> &) =
-                delete;
-        FanInFabric(FanInFabric<MessageType, qsize_expt, IN_THREAD_CNT> &&) =
-                delete;
-        FanInFabric &
-        operator=(FanInFabric<MessageType, qsize_expt, IN_THREAD_CNT> &&) =
-                delete;
+        FanInFabric(const FanInFabric &) = delete;
+        FanInFabric &operator=(const FanInFabric &) = delete;
+        FanInFabric(FanInFabric &&) = delete;
+        FanInFabric &operator=(FanInFabric &&) = delete;
 
         void init() noexcept {
-                for (int i = 0; i < IN_THREAD_CNT; ++i)
+                for (std::size_t i = 0; i < IN_THREAD_CNT; ++i)
                         in_queues[i].init();
                 hint.store(0);
                 dl.init();
@@ -141,7 +180,8 @@ public:
                               "Thread ID out of bounds");
 
                 in_queues[thread_id].flush();
-                hint.fetch_and(~(1 << thread_id), std::memory_order_relaxed);
+                hint.fetch_and(~(BitmapType(1) << thread_id),
+                               std::memory_order_relaxed);
         }
 
         void flush_all() noexcept {
@@ -158,7 +198,7 @@ public:
                               "Thread ID out of bounds");
 
                 return static_cast<FanInFabricSendResult>(static_cast<uint32_t>(
-                        in_queues[thread_id].send(message)));
+                        in_queues[thread_id].send(std::move(message))));
         }
 
         FanInFabricRecvBitmapResult
@@ -178,7 +218,7 @@ public:
                 std::size_t qsize = ((tail + QSIZE_MASK) - head) & QSIZE_MASK;
 
                 if (qsize <= 1)
-                        hint.fetch_and(~(1 << hinted_id),
+                        hint.fetch_and(~(BitmapType(1) << hinted_id),
                                        std::memory_order_relaxed);
 
                 if (qsize) {
@@ -205,7 +245,7 @@ public:
                                 ((tail + QSIZE_MASK) - head) & QSIZE_MASK;
 
                         if (qsize <= 1)
-                                hint.fetch_and(~(1 << hinted_id),
+                                hint.fetch_and(~(BitmapType(1) << hinted_id),
                                                std::memory_order_relaxed);
 
                         if (qsize) {
@@ -241,7 +281,7 @@ public:
                                 ((tail + QSIZE_MASK) - head) & QSIZE_MASK;
 
                         if (qsize <= 1)
-                                hint.fetch_and(~(1 << hinted_id),
+                                hint.fetch_and(~(BitmapType(1) << hinted_id),
                                                std::memory_order_relaxed);
 
                         if (qsize) {
@@ -273,23 +313,23 @@ public:
 
                 uint8_t curr = dl.first;
 
-                if (in_queues[curr].size())
-                        bitmap |= 1 << curr;
+                if (in_queues[curr].get_size())
+                        bitmap |= BitmapType(1) << curr;
 
                 do {
                         curr = dl.next[curr];
-                        if (in_queues[curr].size())
-                                bitmap |= 1 << curr;
+                        if (in_queues[curr].get_size())
+                                bitmap |= BitmapType(1) << curr;
                 } while (curr != dl.last);
 
-                hint.fetch_or(bitmap, std::memory_order_release);
+                hint.fetch_or(bitmap, std::memory_order_relaxed);
         }
 
-        template <std::size_t thread_id> std::size_t size() const noexcept {
+        template <std::size_t thread_id> std::size_t get_size() const noexcept {
                 static_assert(thread_id < IN_THREAD_CNT,
                               "Thread ID out of bounds");
 
-                return in_queues[thread_id].size();
+                return in_queues[thread_id].get_size();
         }
 
         template <std::size_t thread_id> bool is_empty() const noexcept {
@@ -317,7 +357,7 @@ private:
                 uint8_t first;
                 uint8_t last;
                 void init() noexcept {
-                        for (int i = 0; i < IN_THREAD_CNT; ++i) {
+                        for (std::size_t i = 0; i < IN_THREAD_CNT; ++i) {
                                 next[i] = (i + 1) % IN_THREAD_CNT;
                                 prev[i] =
                                         (i + IN_THREAD_CNT - 1) % IN_THREAD_CNT;
@@ -347,7 +387,9 @@ private:
                         }
                 }
         } dl;
+
         std::size_t rotation;
+
         BitmapType rotate(BitmapType bitmap) const noexcept {
                 bitmap &= THREAD_BITMAP_MASK;
 
@@ -360,6 +402,337 @@ private:
         }
 };
 
+template <typename MessageType, std::size_t consumer_qsize_expt,
+          std::size_t BUFFER_SIZE, std::size_t reclaim_qsize_expt,
+          std::size_t OUT_THREAD_CNT>
+class FanOutFabric {
+public:
+        using BitmapType = uint64_t;
+        using RefCountType = uint32_t;
+        using IndexType = uint16_t;
+
+        static constexpr std::size_t CONSUMER_QSIZE = 1ULL
+                                                      << consumer_qsize_expt;
+        static constexpr std::size_t CONSUMER_QSIZE_MASK = CONSUMER_QSIZE - 1;
+        static constexpr std::size_t RECLAIM_QSIZE = 1ULL << reclaim_qsize_expt;
+        static constexpr std::size_t BITMAP_SIZE = sizeof(BitmapType) * 8;
+        static constexpr BitmapType THREAD_BITMAP_MASK =
+                OUT_THREAD_CNT == BITMAP_SIZE
+                        ? ~BitmapType(0)
+                        : (BitmapType(1) << OUT_THREAD_CNT) - 1;
+
+        static_assert(OUT_THREAD_CNT <= BITMAP_SIZE,
+                      "Insufficient bitmap size");
+        static_assert(std::numeric_limits<IndexType>::max() >= BUFFER_SIZE,
+                      "Insuffiently large IndexType");
+
+        FanOutFabric() noexcept {}
+        FanOutFabric(const FanOutFabric &) = delete;
+        FanOutFabric &operator=(const FanOutFabric &) = delete;
+        FanOutFabric(FanOutFabric &&) = delete;
+        FanOutFabric &operator=(FanOutFabric &&) = delete;
+
+        template <std::size_t thread_id> class BorrowedRef {
+        public:
+                static_assert(thread_id < OUT_THREAD_CNT,
+                              "Thread ID out of bounds");
+
+                BorrowedRef() noexcept
+                        : parent(nullptr), slot(BUFFER_SIZE), payload(nullptr),
+                          released(true) {}
+                BorrowedRef(const BorrowedRef &) = delete;
+                BorrowedRef &operator=(const BorrowedRef &) = delete;
+                BorrowedRef(BorrowedRef &&) = delete;
+                BorrowedRef &operator=(BorrowedRef &&) = delete;
+
+                ~BorrowedRef() noexcept {
+                        if (is_valid())
+                                release();
+                }
+
+                void init(FanOutFabric *parent, IndexType slot,
+                          const MessageType *payload) noexcept {
+                        this->parent = parent;
+                        this->slot = slot;
+                        this->payload = payload;
+                        released = false;
+                }
+
+                FanOutFabricDeallocResult release() noexcept {
+                        released = true;
+                        payload = nullptr;
+                        return parent->dealloc_try<thread_id>(slot);
+                }
+
+                bool is_valid() const noexcept {
+                        return !released && payload != nullptr &&
+                               parent != nullptr;
+                }
+
+                bool is_released() const noexcept {
+                        return released || payload == nullptr;
+                }
+
+                const MessageType &get() const noexcept { return *payload; }
+                IndexType get_slot() const noexcept { return slot; }
+
+        private:
+                FanOutFabric *parent;
+                IndexType slot;
+                const MessageType *payload;
+                bool released;
+        };
+
+        void init() noexcept {
+                for (std::size_t i = 0; i < OUT_THREAD_CNT; ++i) {
+                        reclaim_queues[i].init();
+                        consumer_queues[i].init();
+                }
+                reclaim_hint.store(0, std::memory_order_release);
+                fs.init();
+                reclaim_rot = 0;
+        }
+
+        // Prohibitively expensive
+        template <std::size_t thread_id>
+        FanOutFabricDeallocResult flush() noexcept {
+                static_assert(thread_id < OUT_THREAD_CNT,
+                              "Thread ID out of bounds");
+
+                std::size_t head = consumer_queues[thread_id].get_head();
+                std::size_t tail = consumer_queues[thread_id].get_tail();
+                auto &qbuffer = consumer_queues[thread_id].get_buffer();
+
+                for (std::size_t i = head; i != tail;
+                     i = ((i + 1) & CONSUMER_QSIZE_MASK)) {
+                        RefCountType cnt = buffer[qbuffer[i]].count.fetch_sub(
+                                1, std::memory_order_relaxed);
+
+                        if (cnt == 1 && dealloc_try<thread_id>(qbuffer[i]) !=
+                                                FanOutFabricDeallocResult::Ok)
+                                return FanOutFabricDeallocResult::
+                                        ErrReclaimQueueFull;
+                }
+
+                consumer_queues[thread_id].flush();
+                return FanOutFabricDeallocResult();
+        }
+
+        void flush_all() noexcept {
+                for (int i = 0; i < OUT_THREAD_CNT; ++i) {
+                        reclaim_queues[i].flush();
+                        consumer_queues[i].flush();
+                }
+                reclaim_hint.store(0, std::memory_order_release);
+                fs.init();
+                reclaim_rot = 0;
+        }
+
+        template <std::size_t thread_id>
+        BorrowedRef<thread_id> get_empty_borrowed_ref() const noexcept {
+                return BorrowedRef<thread_id>();
+        }
+        IndexType free_get_size() const noexcept { return fs.get_size(); }
+        template <std::size_t thread_id> std::size_t get_size() const noexcept {
+                static_assert(thread_id < OUT_THREAD_CNT,
+                              "Thread ID out of bounds");
+
+                return consumer_queues[thread_id].get_size();
+        }
+
+        FanOutFabricSendResult<BitmapType>
+        send(MessageType &&message, BitmapType policy,
+             IndexType reclaim_budget) noexcept {
+                if (fs.is_empty()) {
+                        reclaim(reclaim_budget);
+
+                        if (fs.is_empty())
+                                return {policy,
+                                        FanOutFabricSendResult<
+                                                BitmapType>::ErrFullFailure};
+                }
+
+                IndexType slot = fs.pop_unsafe();
+                RefCountType failed_cnt = 0;
+                RefCountType try_cnt = std::popcount(policy);
+                buffer[slot].payload = std::move(message);
+                buffer[slot].count.store(try_cnt);
+
+                for (std::size_t i = 0; i < OUT_THREAD_CNT; ++i) {
+                        if ((policy & (BitmapType(1) << i)) &&
+                            consumer_queues[i].send(std::move(slot)) !=
+                                    EndpointQueueSendResult::Ok)
+                                ++failed_cnt;
+                        else
+                                policy &= (~(BitmapType(1) << i)) &
+                                          THREAD_BITMAP_MASK;
+                }
+
+                buffer[slot].count.fetch_sub(failed_cnt,
+                                             std::memory_order_relaxed);
+
+                if (try_cnt == failed_cnt) {
+                        fs.push(slot);
+                        return {policy, FanOutFabricSendResult<
+                                                BitmapType>::ErrFullFailure};
+                } else if (failed_cnt) {
+                        return {policy, FanOutFabricSendResult<
+                                                BitmapType>::ErrPartialSuccess};
+                } else {
+                        return {0, FanOutFabricSendResult<BitmapType>::Ok};
+                }
+        }
+
+        template <std::size_t thread_id>
+        FanOutFabricRecvResult recv(BorrowedRef<thread_id> &token) noexcept {
+                static_assert(thread_id < OUT_THREAD_CNT,
+                              "Thread ID out of bounds");
+
+                std::size_t head = consumer_queues[thread_id].get_head();
+                std::size_t tail = consumer_queues[thread_id].get_tail();
+
+                if (head == tail)
+                        return FanOutFabricRecvResult::ErrEmpty;
+
+                if (token.is_valid())
+                        token.release();
+
+                IndexType slot;
+                consumer_queues[thread_id].recv_unsafe(slot, head);
+
+                token.init(this, slot, &(buffer[slot].payload));
+                return FanOutFabricRecvResult::Ok;
+        }
+
+        IndexType reclaim(IndexType budget) noexcept {
+                IndexType reclaim_cnt = 0;
+
+                BitmapType bitmap =
+                        reclaim_hint.load(std::memory_order_relaxed);
+                bitmap = rotate(bitmap);
+
+                for (std::size_t i = 0;
+                     reclaim_cnt < budget && i < OUT_THREAD_CNT; ++i) {
+                        if (!(bitmap & (BitmapType(1) << i)))
+                                continue;
+
+                        std::size_t idx = (i + reclaim_rot) % OUT_THREAD_CNT;
+
+                        reclaim_hint.fetch_and(~(BitmapType(1) << idx),
+                                               std::memory_order_relaxed);
+
+                        std::size_t head = reclaim_queues[idx].get_head();
+                        std::size_t tail = reclaim_queues[idx].get_tail();
+                        while (reclaim_cnt < budget && head != tail) {
+                                IndexType tmp;
+                                reclaim_queues[idx].recv_unsafe(tmp, head);
+                                fs.push(tmp);
+                                ++reclaim_cnt;
+                        }
+
+                        if (reclaim_cnt >= budget &&
+                            head != reclaim_queues[idx].get_tail())
+                                reclaim_hint.fetch_or(
+                                        BitmapType(1) << idx,
+                                        std::memory_order_relaxed);
+                        reclaim_rot = (idx + 1) % OUT_THREAD_CNT;
+                }
+
+                return reclaim_cnt;
+        }
+        IndexType reclaim_unlimited() noexcept { return reclaim(BUFFER_SIZE); }
+        IndexType reclaim_scan_all(IndexType budget) noexcept {
+                IndexType reclaim_cnt = 0;
+
+                for (std::size_t i = 0;
+                     reclaim_cnt < budget && i < OUT_THREAD_CNT; ++i) {
+                        std::size_t idx = (i + reclaim_rot) % OUT_THREAD_CNT;
+
+                        reclaim_hint.fetch_and(~(BitmapType(1) << idx),
+                                               std::memory_order_relaxed);
+
+                        std::size_t head = reclaim_queues[idx].get_head();
+                        std::size_t tail = reclaim_queues[idx].get_tail();
+                        while (reclaim_cnt < budget && head != tail) {
+                                IndexType tmp;
+                                reclaim_queues[idx].recv_unsafe(tmp, head);
+                                fs.push(tmp);
+                                ++reclaim_cnt;
+                        }
+
+                        if (reclaim_cnt >= budget &&
+                            head != reclaim_queues[idx].get_tail())
+                                reclaim_hint.fetch_or(
+                                        BitmapType(1) << idx,
+                                        std::memory_order_relaxed);
+                        reclaim_rot = (idx + 1) % OUT_THREAD_CNT;
+                }
+
+                return reclaim_cnt;
+        }
+
+        template <std::size_t thread_id>
+        FanOutFabricDeallocResult dealloc_try(IndexType slot) noexcept {
+                static_assert(thread_id < OUT_THREAD_CNT,
+                              "Thread ID out of bounds");
+
+                auto res = reclaim_queues[thread_id].send(std::move(slot));
+                if (res == EndpointQueueSendResult::Ok) {
+                        reclaim_hint.fetch_or(BitmapType(1) << thread_id,
+                                              std::memory_order_relaxed);
+                        return FanOutFabricDeallocResult::Ok;
+                } else {
+                        return FanOutFabricDeallocResult::ErrReclaimQueueFull;
+                }
+        }
+
+private:
+        std::array<EndpointQueue<IndexType, reclaim_qsize_expt>, OUT_THREAD_CNT>
+                reclaim_queues;
+        std::array<EndpointQueue<IndexType, consumer_qsize_expt>,
+                   OUT_THREAD_CNT>
+                consumer_queues;
+        alignas(CLS) std::atomic<BitmapType> reclaim_hint;
+        struct BufferSlot {
+                alignas(CLS) MessageType payload;
+                alignas(CLS) std::atomic<RefCountType> count;
+        };
+        std::array<BufferSlot, BUFFER_SIZE> buffer;
+        struct alignas(CLS) FreeStack {
+                std::array<IndexType, BUFFER_SIZE> free;
+                int top;
+                void init() {
+                        for (std::size_t i = 0; i < BUFFER_SIZE; ++i)
+                                free[i] = i;
+                        top = BUFFER_SIZE;
+                }
+                void push(IndexType val) {
+                        free[top] = val;
+                        ++top;
+                }
+                IndexType pop() {
+                        if (top)
+                                return free[--top];
+                        return BUFFER_SIZE;
+                }
+                IndexType pop_unsafe() { return free[--top]; }
+                bool is_empty() const { return top == 0; }
+                int get_size() const { return top; }
+        } fs;
+        std::size_t reclaim_rot;
+
+        BitmapType rotate(BitmapType bitmap) const noexcept {
+                bitmap &= THREAD_BITMAP_MASK;
+
+                if (reclaim_rot == 0)
+                        return bitmap;
+
+                return ((bitmap >> reclaim_rot) |
+                        (bitmap << (OUT_THREAD_CNT - reclaim_rot))) &
+                       THREAD_BITMAP_MASK;
+        }
+};
+
 } // namespace THWeaver
 
 #endif

tests/fan_in/basic_test.cc

@@ -0,0 +1,161 @@
+#include <atomic>
+#include <chrono>
+#include <cstdint>
+#include <iostream>
+#include <thread>
+#include <vector>
+
+#include <weaver.h>
+
+using std::chrono::nanoseconds;
+
+constexpr std::size_t kThreads = 2;
+
+uint64_t pack_message(uint32_t producer, uint32_t seq) {
+        return (static_cast<uint64_t>(producer) << 32) |
+               static_cast<uint64_t>(seq);
+}
+
+void unpack_message(uint64_t value, uint32_t &producer, uint32_t &seq) {
+        producer = static_cast<uint32_t>(value >> 32);
+        seq = static_cast<uint32_t>(value & 0xffffffffu);
+}
+
+using std::chrono::nanoseconds;
+using std::chrono::steady_clock;
+
+int main() {
+        int n = 0;
+        if (!(std::cin >> n) || n <= 0) {
+                std::cerr << "n must be positive\n";
+                return 1;
+        }
+
+        using Fabric = THWeaver::FanInFabric<uint64_t, 10, kThreads>;
+        Fabric fabric;
+        fabric.init();
+
+        std::atomic<bool> failed(false);
+
+        std::vector<int64_t> send_time0(n, -1);
+        std::vector<int64_t> send_time1(n, -1);
+        std::vector<int64_t> recv_time0(n, -1);
+        std::vector<int64_t> recv_time1(n, -1);
+
+        std::thread producer0([&]() {
+                for (int i = 1; i <= n && !failed.load(); ++i) {
+                        while (true) {
+                                auto now =
+                                        std::chrono::steady_clock::now()
+                                                .time_since_epoch();
+                                auto ns =
+                                        std::chrono::duration_cast<nanoseconds>(
+                                                now)
+                                                .count();
+                                if (fabric.send<0>(pack_message(0, i)) ==
+                                    THWeaver::FanInFabricSendResult::Ok) {
+                                        send_time0[i - 1] = ns;
+                                        break;
+                                }
+                        }
+                }
+        });
+
+        std::thread producer1([&]() {
+                for (int i = 1; i <= n && !failed.load(); ++i) {
+                        while (true) {
+                                auto now =
+                                        std::chrono::steady_clock::now()
+                                                .time_since_epoch();
+                                auto ns =
+                                        std::chrono::duration_cast<nanoseconds>(
+                                                now)
+                                                .count();
+                                if (fabric.send<1>(pack_message(1, i)) ==
+                                    THWeaver::FanInFabricSendResult::Ok) {
+                                        send_time1[i - 1] = ns;
+                                        break;
+                                }
+                        }
+                }
+        });
+
+        std::thread consumer([&]() {
+                std::vector<uint32_t> expected(kThreads, 1);
+                std::size_t received = 0;
+                const std::size_t total =
+                        static_cast<std::size_t>(n) * kThreads;
+
+                while (received < total && !failed.load()) {
+                        uint64_t value = 0;
+                        auto res = fabric.recv_try(value);
+                        if (res == THWeaver::FanInFabricRecvTryResult::Ok) {
+                                uint32_t producer = 0;
+                                uint32_t seq = 0;
+                                unpack_message(value, producer, seq);
+
+                                if (producer >= kThreads ||
+                                    seq != expected[producer]) {
+                                        std::cerr
+                                                << "fan-in mismatch: producer "
+                                                << producer << " expected "
+                                                << expected[producer] << " got "
+                                                << seq << "\n";
+                                        failed.store(true);
+                                        break;
+                                }
+
+                                if (producer == 0) {
+                                        auto recv_time =
+                                                std::chrono::steady_clock::now()
+                                                        .time_since_epoch();
+                                        auto recv_ns =
+                                                std::chrono::duration_cast<
+                                                        nanoseconds>(recv_time)
+                                                        .count();
+                                        recv_time0[seq - 1] = recv_ns;
+                                } else {
+                                        auto recv_time =
+                                                std::chrono::steady_clock::now()
+                                                        .time_since_epoch();
+                                        auto recv_ns =
+                                                std::chrono::duration_cast<
+                                                        nanoseconds>(recv_time)
+                                                        .count();
+                                        recv_time1[seq - 1] = recv_ns;
+                                }
+
+                                ++expected[producer];
+                                ++received;
+                                continue;
+                        }
+
+                        Fabric::BitmapType bitmap = 0;
+                        fabric.full_scan(bitmap);
+                }
+        });
+
+        producer0.join();
+        producer1.join();
+        consumer.join();
+
+        if (failed.load()) {
+                return 1;
+        }
+
+        for (int i = 1; i <= n; ++i) {
+                uint64_t payload0 = pack_message(0, i);
+                uint64_t payload1 = pack_message(1, i);
+
+                int64_t send_ns0 = send_time0[i - 1];
+                int64_t recv_ns0 = recv_time0[i - 1];
+                int64_t send_ns1 = send_time1[i - 1];
+                int64_t recv_ns1 = recv_time1[i - 1];
+
+                std::cout << payload0 << ","
+                          << (recv_ns0 - send_ns0) << "\n";
+                std::cout << payload1 << ","
+                          << (recv_ns1 - send_ns1) << "\n";
+        }
+        return 0;
+}

tests/fan_out/basic_test.cc

@@ -0,0 +1,134 @@
+#include <atomic>
+#include <chrono>
+#include <cstdint>
+#include <iostream>
+#include <thread>
+#include <vector>
+
+#include <weaver.h>
+
+constexpr std::size_t kConsumers = 2;
+constexpr std::size_t kBufferSize = 256;
+
+using std::chrono::nanoseconds;
+using std::chrono::steady_clock;
+
+int main() {
+        int n = 0;
+        if (!(std::cin >> n) || n <= 0) {
+                std::cerr << "n must be positive\n";
+                return 1;
+        }
+
+        using Fabric =
+                THWeaver::FanOutFabric<uint64_t, 8, kBufferSize, 8, kConsumers>;
+        Fabric fabric;
+        fabric.init();
+
+        std::atomic<bool> failed(false);
+        std::atomic<int> consumed0(0);
+        std::atomic<int> consumed1(0);
+        std::vector<int64_t> send_time(n, -1);
+        std::vector<int64_t> recv_time0(n, -1);
+        std::vector<int64_t> recv_time1(n, -1);
+
+        std::thread consumer0([&]() {
+                auto token = fabric.get_empty_borrowed_ref<0>();
+                int expected = 1;
+                while (expected <= n && !failed.load()) {
+                        if (fabric.recv<0>(token) !=
+                            THWeaver::FanOutFabricRecvResult::Ok) {
+                                continue;
+                        }
+                        if (token.get() != static_cast<uint64_t>(expected)) {
+                                std::cerr << "fan-out mismatch on consumer 0: "
+                                          << "expected " << expected << " got "
+                                          << token.get() << "\n";
+                                failed.store(true);
+                                break;
+                        }
+                        auto recv_time = steady_clock::now().time_since_epoch();
+                        auto recv_ns =
+                                std::chrono::duration_cast<nanoseconds>(
+                                        recv_time)
+                                        .count();
+                        recv_time0[expected - 1] = recv_ns;
+                        token.release();
+                        consumed0.store(expected);
+                        ++expected;
+                }
+        });
+
+        std::thread consumer1([&]() {
+                auto token = fabric.get_empty_borrowed_ref<1>();
+                int expected = 1;
+                while (expected <= n && !failed.load()) {
+                        if (fabric.recv<1>(token) !=
+                            THWeaver::FanOutFabricRecvResult::Ok) {
+                                continue;
+                        }
+                        if (token.get() != static_cast<uint64_t>(expected)) {
+                                std::cerr << "fan-out mismatch on consumer 1: "
+                                          << "expected " << expected << " got "
+                                          << token.get() << "\n";
+                                failed.store(true);
+                                break;
+                        }
+                        auto recv_time = steady_clock::now().time_since_epoch();
+                        auto recv_ns =
+                                std::chrono::duration_cast<nanoseconds>(
+                                        recv_time)
+                                        .count();
+                        recv_time1[expected - 1] = recv_ns;
+                        token.release();
+                        consumed1.store(expected);
+                        ++expected;
+                }
+        });
+
+        constexpr uint64_t policy = (1ULL << 0) | (1ULL << 1);
+
+        for (int i = 1; i <= n && !failed.load(); ++i) {
+                while (!failed.load()) {
+                        auto now = steady_clock::now().time_since_epoch();
+                        auto ns = std::chrono::duration_cast<nanoseconds>(now)
+                                          .count();
+                        auto res = fabric.send(static_cast<uint64_t>(i), policy,
+                                               kBufferSize);
+                        if (res.result ==
+                            THWeaver::FanOutFabricSendResult<uint64_t>::Ok) {
+                                send_time[i - 1] = ns;
+                                break;
+                        }
+                        if (res.result ==
+                            THWeaver::FanOutFabricSendResult<
+                                    uint64_t>::ErrPartialSuccess) {
+                                std::cerr << "fan-out partial success for "
+                                          << "message " << i << "\n";
+                                failed.store(true);
+                                break;
+                        }
+                }
+
+                while (!failed.load() &&
+                       (consumed0.load() < i || consumed1.load() < i)) {
+                }
+        }
+
+        consumer0.join();
+        consumer1.join();
+
+        if (failed.load()) {
+                return 1;
+        }
+
+        for (int i = 1; i <= n; ++i) {
+                int64_t send_ns = send_time[i - 1];
+                int64_t recv_ns0 = recv_time0[i - 1];
+                int64_t recv_ns1 = recv_time1[i - 1];
+
+                std::cout << i << "," << (recv_ns0 - send_ns) << "\n";
+                std::cout << i << "," << (recv_ns1 - send_ns) << "\n";
+        }
+        return 0;
+}