initial commit

tdutils/td/utils/MpscLinkQueue.h

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+/*
+    This file is part of TON Blockchain Library.
+
+    TON Blockchain Library is free software: you can redistribute it and/or modify
+    it under the terms of the GNU Lesser General Public License as published by
+    the Free Software Foundation, either version 2 of the License, or
+    (at your option) any later version.
+
+    TON Blockchain Library is distributed in the hope that it will be useful,
+    but WITHOUT ANY WARRANTY; without even the implied warranty of
+    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+    GNU Lesser General Public License for more details.
+
+    You should have received a copy of the GNU Lesser General Public License
+    along with TON Blockchain Library.  If not, see <http://www.gnu.org/licenses/>.
+
+    Copyright 2017-2019 Telegram Systems LLP
+*/
+#pragma once
+
+#include "td/utils/common.h"
+
+#include <atomic>
+
+namespace td {
+//NB: holder of the queue holds all responsibility of freeing its nodes
+class MpscLinkQueueImpl {
+ public:
+  class Node;
+  class Reader;
+
+  void push(Node *node) {
+    node->next_ = head_.load(std::memory_order_relaxed);
+    while (!head_.compare_exchange_strong(node->next_, node, std::memory_order_release, std::memory_order_relaxed)) {
+    }
+  }
+
+  void push_unsafe(Node *node) {
+    node->next_ = head_.load(std::memory_order_relaxed);
+    head_.store(node, std::memory_order_relaxed);
+  }
+
+  void pop_all(Reader &reader) {
+    return reader.add(head_.exchange(nullptr, std::memory_order_acquire));
+  }
+
+  void pop_all_unsafe(Reader &reader) {
+    return reader.add(head_.exchange(nullptr, std::memory_order_relaxed));
+  }
+
+  class Node {
+    friend class MpscLinkQueueImpl;
+    Node *next_{nullptr};
+  };
+
+  class Reader {
+   public:
+    Node *read() {
+      auto old_head = head_;
+      if (head_) {
+        head_ = head_->next_;
+      }
+      return old_head;
+    }
+    void delay(Node *node) {
+      node->next_ = head_;
+      if (!head_) {
+        tail_ = node;
+      }
+      head_ = node;
+    }
+    size_t calc_size() const {
+      size_t res = 0;
+      for (auto it = head_; it != nullptr; it = it->next_, res++) {
+      }
+      return res;
+    }
+
+   private:
+    friend class MpscLinkQueueImpl;
+    void add(Node *node) {
+      if (node == nullptr) {
+        return;
+      }
+      // Reverse list
+      Node *tail = node;
+      Node *head = nullptr;
+      while (node) {
+        auto next = node->next_;
+        node->next_ = head;
+        head = node;
+        node = next;
+      }
+      if (head_ == nullptr) {
+        head_ = head;
+      } else {
+        tail_->next_ = head;
+      }
+      tail_ = tail;
+    }
+    Node *head_{nullptr};
+    Node *tail_{nullptr};
+  };
+
+ private:
+  std::atomic<Node *> head_{nullptr};
+};
+
+// Uses MpscLinkQueueImpl.
+// Node should have to_mpsc_link_queue_node and from_mpsc_link_queue_node functions
+template <class Node>
+class MpscLinkQueue {
+ public:
+  void push(Node node) {
+    impl_.push(node.to_mpsc_link_queue_node());
+  }
+  void push_unsafe(Node node) {
+    impl_.push_unsafe(node.to_mpsc_link_queue_node());
+  }
+  class Reader {
+   public:
+    ~Reader() {
+      CHECK(!read());
+    }
+    Node read() {
+      auto node = impl_.read();
+      if (!node) {
+        return {};
+      }
+      return Node::from_mpsc_link_queue_node(node);
+    }
+    void delay(Node node) {
+      impl_.delay(node.to_mpsc_link_queue_node());
+    }
+    size_t calc_size() const {
+      return impl_.calc_size();
+    }
+
+   private:
+    friend class MpscLinkQueue;
+
+    MpscLinkQueueImpl::Reader impl_;
+    MpscLinkQueueImpl::Reader &impl() {
+      return impl_;
+    }
+  };
+
+  void pop_all(Reader &reader) {
+    return impl_.pop_all(reader.impl());
+  }
+  void pop_all_unsafe(Reader &reader) {
+    return impl_.pop_all_unsafe(reader.impl());
+  }
+
+ private:
+  MpscLinkQueueImpl impl_;
+};
+
+template <class Value>
+class MpscLinkQueueUniquePtrNode {
+ public:
+  MpscLinkQueueUniquePtrNode() = default;
+  explicit MpscLinkQueueUniquePtrNode(unique_ptr<Value> ptr) : ptr_(std::move(ptr)) {
+  }
+
+  MpscLinkQueueImpl::Node *to_mpsc_link_queue_node() {
+    return ptr_.release()->to_mpsc_link_queue_node();
+  }
+  static MpscLinkQueueUniquePtrNode<Value> from_mpsc_link_queue_node(td::MpscLinkQueueImpl::Node *node) {
+    return MpscLinkQueueUniquePtrNode<Value>(unique_ptr<Value>(Value::from_mpsc_link_queue_node(node)));
+  }
+
+  explicit operator bool() {
+    return ptr_ != nullptr;
+  }
+
+  Value &value() {
+    return *ptr_;
+  }
+
+ private:
+  unique_ptr<Value> ptr_;
+};
+
+}  // namespace td