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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).
//
#pragma once
#include <memory>
#include "db/blob/blob_log_format.h"
#include "rocksdb/slice.h"
#define MAX_HEADER_SIZE(a, b, c) (a > b ? (a > c ? a : c) : (b > c ? b : c))
namespace ROCKSDB_NAMESPACE {
class RandomAccessFileReader;
class Env;
class Statistics;
class Status;
class SystemClock;
/**
* BlobLogSequentialReader is a general purpose log stream reader
* implementation. The actual job of reading from the device is implemented by
* the RandomAccessFileReader interface.
*
* Please see BlobLogWriter for details on the file and record layout.
*/
class BlobLogSequentialReader {
public:
enum ReadLevel {
kReadHeader,
kReadHeaderKey,
kReadHeaderKeyBlob,
};
// Create a reader that will return log records from "*file_reader".
BlobLogSequentialReader(std::unique_ptr<RandomAccessFileReader>&& file_reader,
SystemClock* clock, Statistics* statistics);
// No copying allowed
BlobLogSequentialReader(const BlobLogSequentialReader&) = delete;
BlobLogSequentialReader& operator=(const BlobLogSequentialReader&) = delete;
~BlobLogSequentialReader();
Status ReadHeader(BlobLogHeader* header);
// Read the next record into *record. Returns true if read
// successfully, false if we hit end of the input. The contents filled in
// *record will only be valid until the next mutating operation on this
// reader.
// If blob_offset is non-null, return offset of the blob through it.
Status ReadRecord(BlobLogRecord* record, ReadLevel level = kReadHeader,
uint64_t* blob_offset = nullptr);
Status ReadFooter(BlobLogFooter* footer);
void ResetNextByte() { next_byte_ = 0; }
uint64_t GetNextByte() const { return next_byte_; }
private:
Status ReadSlice(uint64_t size, Slice* slice, char* buf);
const std::unique_ptr<RandomAccessFileReader> file_;
SystemClock* clock_;
Statistics* statistics_;
Slice buffer_;
char header_buf_[MAX_HEADER_SIZE(BlobLogHeader::kSize, BlobLogFooter::kSize,
BlobLogRecord::kHeaderSize)];
// which byte to read next
uint64_t next_byte_;
};
} // namespace ROCKSDB_NAMESPACE
#undef MAX_HEADER_SIZE
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