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// 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 "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<FSSequentialFile> file_;
std::string file_name_;
std::atomic<size_t> offset_{0}; // read offset
public:
explicit SequentialFileReader(std::unique_ptr<FSSequentialFile>&& _file,
const std::string& _file_name)
: file_(std::move(_file)), file_name_(_file_name) {}
explicit SequentialFileReader(std::unique_ptr<FSSequentialFile>&& _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<FSSequentialFile> NewReadaheadSequentialFile(
std::unique_ptr<FSSequentialFile>&& file, size_t readahead_size);
};
} // namespace ROCKSDB_NAMESPACE
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