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59 lines
1.7 KiB
59 lines
1.7 KiB
#ifndef LEVELDB_VLOG_READER_H
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#define LEVELDB_VLOG_READER_H
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#include <cstdint>
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#include "db/log_format.h"
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#include "leveldb/slice.h"
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#include "leveldb/status.h"
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namespace leveldb {
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class SequentialFile;
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class RandomAccessFile;
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namespace log {
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class VlogReader {
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public:
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class Reporter {
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public:
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virtual ~Reporter() = default;
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virtual void Corruption(size_t bytes, const Status& status) = 0;
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};
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// 支持随机读与顺序读，提升顺序读取的效率
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explicit VlogReader(SequentialFile* file, Reporter* reporter);
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explicit VlogReader(RandomAccessFile* file, Reporter* reporter);
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VlogReader(const VlogReader&) = delete;
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VlogReader& operator=(const VlogReader&) = delete;
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~VlogReader();
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// 从 vlog 中读取一条具体的值
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bool ReadValue(uint64_t offset, size_t length, Slice* key_value, char* scratch);
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bool ReadRecord(Slice* record, std::string* scratch);
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// 返回 ReadRecord 函数读取的最后一条 record 的偏移（last_record_offset_）
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uint64_t LastRecordOffset() const;
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private:
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/* 读取 vlog 物理记录（ data 部分） */
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bool ReadPhysicalRecord(std::string* result);
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void ReportCorruption(uint64_t bytes, const Status &reason);
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SequentialFile* const file_;
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RandomAccessFile* const file_random_;
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Reporter* const reporter_;
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char* const backing_store_;
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Slice buffer_;
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bool eof_; // Last Read() indicated EOF by returning < kBlockSize
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// Offset of the last record returned by ReadRecord.
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uint64_t last_record_offset_;
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};
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} // namespace log
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} // namespace leveldb
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#endif // LEVELDB_VLOG_READER_H
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