// Copyright (c) 2011-present, Facebook, Inc. All rights reserved. // This source code is licensed under both the GPLv2 (found in the // COPYING file in the root directory) and Apache 2.0 License // (found in the LICENSE.Apache file in the root directory). // // Copyright (c) 2011 The LevelDB Authors. All rights reserved. // Use of this source code is governed by a BSD-style license that can be // found in the LICENSE file. See the AUTHORS file for names of contributors. #pragma once #include #include #include "port/port.h" #include "rocksdb/env.h" #include "rocksdb/file_system.h" namespace ROCKSDB_NAMESPACE { // SequentialFileReader is a wrapper on top of Env::SequentialFile. It handles // Buffered (i.e when page cache is enabled) and Direct (with O_DIRECT / page // cache disabled) reads appropriately, and also updates the IO stats. class SequentialFileReader { private: std::unique_ptr file_; std::string file_name_; std::atomic offset_{0}; // read offset public: explicit SequentialFileReader(std::unique_ptr&& _file, const std::string& _file_name) : file_(std::move(_file)), file_name_(_file_name) {} explicit SequentialFileReader(std::unique_ptr&& _file, const std::string& _file_name, size_t _readahead_size) : file_(NewReadaheadSequentialFile(std::move(_file), _readahead_size)), file_name_(_file_name) {} SequentialFileReader(SequentialFileReader&& o) ROCKSDB_NOEXCEPT { *this = std::move(o); } SequentialFileReader& operator=(SequentialFileReader&& o) ROCKSDB_NOEXCEPT { file_ = std::move(o.file_); return *this; } SequentialFileReader(const SequentialFileReader&) = delete; SequentialFileReader& operator=(const SequentialFileReader&) = delete; Status Read(size_t n, Slice* result, char* scratch); Status Skip(uint64_t n); FSSequentialFile* file() { return file_.get(); } std::string file_name() { return file_name_; } bool use_direct_io() const { return file_->use_direct_io(); } private: // NewReadaheadSequentialFile provides a wrapper over SequentialFile to // always prefetch additional data with every read. static std::unique_ptr NewReadaheadSequentialFile( std::unique_ptr&& file, size_t readahead_size); }; } // namespace ROCKSDB_NAMESPACE