RecordIO.h

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/*
 * Copyright 2013-present Facebook, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#pragma once
#define FOLLY_IO_RECORDIO_H_

#include <atomic>
#include <memory>
#include <mutex>

#include <folly/File.h>
#include <folly/Range.h>
#include <folly/io/IOBuf.h>
#include <folly/system/MemoryMapping.h>

namespace folly {

class RecordIOWriter {
 public:
  explicit RecordIOWriter(File file, uint32_t fileId = 1);

  void write(std::unique_ptr<IOBuf> buf);

  off_t filePos() const {
    return filePos_;
  }

 private:
  File file_;
  uint32_t fileId_;
  std::unique_lock<File> writeLock_;
  std::atomic<off_t> filePos_;
};

class RecordIOReader {
 public:
  class Iterator;

  typedef Iterator iterator;
  typedef Iterator const_iterator;
  typedef std::pair<ByteRange, off_t> value_type;
  typedef value_type& reference;
  typedef const value_type& const_reference;

  explicit RecordIOReader(File file, uint32_t fileId = 0);

  Iterator cbegin() const;
  Iterator begin() const;
  Iterator cend() const;
  Iterator end() const;

  Iterator seek(off_t pos) const;

 private:
  MemoryMapping map_;
  uint32_t fileId_;
};

namespace recordio_helpers {

// We're exposing the guts of the RecordIO implementation for two reasons:
// 1. It makes unit testing easier, and
// 2. It allows you to build different RecordIO readers / writers that use
// different storage systems underneath (not standard files)

constexpr size_t headerSize(); // defined in RecordIO-inl.h

size_t prependHeader(std::unique_ptr<IOBuf>& buf, uint32_t fileId = 1);

struct RecordInfo {
  uint32_t fileId;
  ByteRange record;
};
RecordInfo
findRecord(ByteRange searchRange, ByteRange wholeRange, uint32_t fileId);

RecordInfo findRecord(ByteRange range, uint32_t fileId);

RecordInfo validateRecord(ByteRange range, uint32_t fileId);

} // namespace recordio_helpers

} // namespace folly

#include <folly/io/RecordIO-inl.h>