rocksdb/file/sequence_file_reader.h
mrambacher 4a09d632c4 Remove Legacy and Custom FileWrapper classes from header files (#7851)
Summary:
Removed the uses of the Legacy FileWrapper classes from the source code.  The wrappers were creating an additional layer of indirection/wrapping, as the Env already has a FileSystem.

Moved the Custom FileWrapper classes into the CustomEnv, as these classes are really for the private use the the CustomEnv class.

Pull Request resolved: https://github.com/facebook/rocksdb/pull/7851

Reviewed By: anand1976

Differential Revision: D26114816

Pulled By: mrambacher

fbshipit-source-id: db32840e58d969d3a0fa6c25aaf13d6dcdc74150
2021-01-28 22:10:32 -08:00

69 lines
2.6 KiB
C++

// 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 <atomic>
#include <string>
#include "env/file_system_tracer.h"
#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::string file_name_;
FSSequentialFilePtr file_;
std::atomic<size_t> offset_{0}; // read offset
public:
explicit SequentialFileReader(
std::unique_ptr<FSSequentialFile>&& _file, const std::string& _file_name,
const std::shared_ptr<IOTracer>& io_tracer = nullptr)
: file_name_(_file_name),
file_(std::move(_file), io_tracer, _file_name) {}
explicit SequentialFileReader(
std::unique_ptr<FSSequentialFile>&& _file, const std::string& _file_name,
size_t _readahead_size,
const std::shared_ptr<IOTracer>& io_tracer = nullptr)
: file_name_(_file_name),
file_(NewReadaheadSequentialFile(std::move(_file), _readahead_size),
io_tracer, _file_name) {}
static Status Create(const std::shared_ptr<FileSystem>& fs,
const std::string& fname, const FileOptions& file_opts,
std::unique_ptr<SequentialFileReader>* reader,
IODebugContext* dbg);
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<FSSequentialFile> NewReadaheadSequentialFile(
std::unique_ptr<FSSequentialFile>&& file, size_t readahead_size);
};
} // namespace ROCKSDB_NAMESPACE