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include/download/reader_pool.hpp

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+/*
+  Copyright <2018-2022> <scott.e.graves@protonmail.com>
+
+  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 INCLUDE_DOWNLOAD_READER_POOL_HPP_
+#define INCLUDE_DOWNLOAD_READER_POOL_HPP_
+
+#include "common.hpp"
+#include "types/repertory.hpp"
+
+namespace repertory {
+class reader_pool final {
+public:
+  typedef std::function<void(api_error error)> completed_callback;
+
+private:
+  struct pool_work_item {
+    pool_work_item(std::string api_path, const std::size_t &read_size,
+                   const std::uint64_t &read_offset, std::vector<char> &data,
+                   completed_callback completed)
+        : api_path(std::move(api_path)), read_size(read_size), read_offset(read_offset), data(data),
+          completed(completed) {}
+
+    std::string api_path;
+    std::size_t read_size;
+    std::uint64_t read_offset;
+    std::vector<char> &data;
+    completed_callback completed;
+  };
+
+public:
+  reader_pool(const std::size_t &pool_size, const api_reader_callback &api_reader)
+      : pool_size_(pool_size), api_reader_(api_reader) {
+    start();
+  }
+
+  ~reader_pool() { stop(); }
+
+private:
+  const std::size_t pool_size_;
+  const api_reader_callback &api_reader_;
+  bool paused_ = false;
+  bool restart_active_ = false;
+  bool stop_requested_ = false;
+  std::mutex work_mutex_;
+  std::condition_variable work_notify_;
+  std::deque<std::shared_ptr<pool_work_item>> work_queue_;
+  std::vector<std::thread> work_threads_;
+  std::uint16_t active_count_ = 0u;
+
+private:
+  void process_work_item(pool_work_item &work);
+
+  void start();
+
+  void stop();
+
+  void wait_for_resume(unique_mutex_lock &lock);
+
+public:
+  void pause();
+
+  void queue_read_bytes(const std::string &api_path, const std::size_t &read_size,
+                        const std::uint64_t &read_offset, std::vector<char> &data,
+                        completed_callback completed);
+
+  void restart();
+
+  void resume();
+};
+} // namespace repertory
+
+#endif // INCLUDE_DOWNLOAD_READER_POOL_HPP_