mirror of https://github.com/facebook/rocksdb.git
94 lines
2.7 KiB
C
94 lines
2.7 KiB
C
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// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
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// This source code is licensed under the BSD-style license found in the
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// LICENSE file in the root directory of this source tree. An additional grant
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// of patent rights can be found in the PATENTS file in the same directory.
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//
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#pragma once
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#ifndef ROCKSDB_LITE
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#include <cstdint>
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#include <memory>
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#include <string>
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#include "rocksdb/options.h"
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#include "rocksdb/slice.h"
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#include "rocksdb/status.h"
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#include "utilities/blob_db/blob_log_format.h"
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namespace rocksdb {
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class SequentialFileReader;
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class Logger;
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namespace blob_db {
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/**
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* Reader is a general purpose log stream reader implementation. The actual job
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* of reading from the device is implemented by the SequentialFile interface.
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*
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* Please see Writer for details on the file and record layout.
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*/
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class Reader {
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public:
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enum ReadLevel {
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kReadHdrFooter,
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kReadHdrKeyFooter,
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kReadHdrKeyBlobFooter,
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};
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// Create a reader that will return log records from "*file".
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// "*file" must remain live while this Reader is in use.
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//
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// If "reporter" is non-nullptr, it is notified whenever some data is
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// dropped due to a detected corruption. "*reporter" must remain
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// live while this Reader is in use.
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//
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// If "checksum" is true, verify checksums if available.
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//
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// The Reader will start reading at the first record located at physical
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// position >= initial_offset within the file.
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Reader(std::shared_ptr<Logger> info_log,
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std::unique_ptr<SequentialFileReader>&& file);
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~Reader();
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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. May use
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// "*scratch" as temporary storage. The contents filled in *record
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// will only be valid until the next mutating operation on this
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// reader or the next mutation to *scratch.
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Status ReadRecord(BlobLogRecord* record, ReadLevel level = kReadHdrFooter,
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WALRecoveryMode wal_recovery_mode =
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WALRecoveryMode::kTolerateCorruptedTailRecords);
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SequentialFileReader* file() { return file_.get(); }
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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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char* GetReadBuffer() { return &(backing_store_[0]); }
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private:
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std::shared_ptr<Logger> info_log_;
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const std::unique_ptr<SequentialFileReader> file_;
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std::string backing_store_;
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Slice buffer_;
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// which byte to read next. For asserting proper usage
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uint64_t next_byte_;
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// No copying allowed
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Reader(const Reader&) = delete;
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Reader& operator=(const Reader&) = delete;
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};
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} // namespace blob_db
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} // namespace rocksdb
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#endif // ROCKSDB_LITE
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