mirror of https://github.com/facebook/rocksdb.git
83 lines
2.4 KiB
C++
83 lines
2.4 KiB
C++
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under both the GPLv2 (found in the
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// COPYING file in the root directory) and Apache 2.0 License
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// (found in the LICENSE.Apache file in the root directory).
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//
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#pragma once
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#include <memory>
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#include "db/blob/blob_log_format.h"
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#include "rocksdb/slice.h"
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#define MAX_HEADER_SIZE(a, b, c) (a > b ? (a > c ? a : c) : (b > c ? b : c))
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namespace ROCKSDB_NAMESPACE {
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class RandomAccessFileReader;
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class Env;
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class Statistics;
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class Status;
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class SystemClock;
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/**
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* BlobLogSequentialReader is a general purpose log stream reader
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* implementation. The actual job of reading from the device is implemented by
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* the RandomAccessFileReader interface.
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*
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* Please see BlobLogWriter for details on the file and record layout.
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*/
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class BlobLogSequentialReader {
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public:
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enum ReadLevel {
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kReadHeader,
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kReadHeaderKey,
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kReadHeaderKeyBlob,
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};
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// Create a reader that will return log records from "*file_reader".
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BlobLogSequentialReader(std::unique_ptr<RandomAccessFileReader>&& file_reader,
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SystemClock* clock, Statistics* statistics);
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// No copying allowed
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BlobLogSequentialReader(const BlobLogSequentialReader&) = delete;
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BlobLogSequentialReader& operator=(const BlobLogSequentialReader&) = delete;
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~BlobLogSequentialReader();
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Status ReadHeader(BlobLogHeader* header);
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// Read the next record into *record. Returns true if read
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// successfully, false if we hit end of the input. The contents filled in
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// *record will only be valid until the next mutating operation on this
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// reader.
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// If blob_offset is non-null, return offset of the blob through it.
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Status ReadRecord(BlobLogRecord* record, ReadLevel level = kReadHeader,
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uint64_t* blob_offset = nullptr);
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Status ReadFooter(BlobLogFooter* footer);
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void ResetNextByte() { next_byte_ = 0; }
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uint64_t GetNextByte() const { return next_byte_; }
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private:
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Status ReadSlice(uint64_t size, Slice* slice, char* buf);
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const std::unique_ptr<RandomAccessFileReader> file_;
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SystemClock* clock_;
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Statistics* statistics_;
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Slice buffer_;
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char header_buf_[MAX_HEADER_SIZE(BlobLogHeader::kSize, BlobLogFooter::kSize,
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BlobLogRecord::kHeaderSize)];
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// which byte to read next
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uint64_t next_byte_;
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};
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} // namespace ROCKSDB_NAMESPACE
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#undef MAX_HEADER_SIZE |