| // Copyright (c) 2011 The LevelDB Authors. All rights reserved. |
| // Use of this source code is governed by a BSD-style license that can be |
| // found in the LICENSE file. See the AUTHORS file for names of contributors. |
| |
| #ifndef STORAGE_LEVELDB_DB_LOG_READER_H_ |
| #define STORAGE_LEVELDB_DB_LOG_READER_H_ |
| |
| #include <stdint.h> |
| |
| #include "db/log_format.h" |
| #include "leveldb/slice.h" |
| #include "leveldb/status.h" |
| |
| namespace leveldb { |
| |
| class SequentialFile; |
| |
| namespace log { |
| |
| class Reader { |
| public: |
| // Interface for reporting errors. |
| class Reporter { |
| public: |
| virtual ~Reporter(); |
| |
| // Some corruption was detected. "size" is the approximate number |
| // of bytes dropped due to the corruption. |
| virtual void Corruption(size_t bytes, const Status& status) = 0; |
| }; |
| |
| // Create a reader that will return log records from "*file". |
| // "*file" must remain live while this Reader is in use. |
| // |
| // If "reporter" is non-NULL, it is notified whenever some data is |
| // dropped due to a detected corruption. "*reporter" must remain |
| // live while this Reader is in use. |
| // |
| // If "checksum" is true, verify checksums if available. |
| // |
| // The Reader will start reading at the first record located at physical |
| // position >= initial_offset within the file. |
| Reader(SequentialFile* file, Reporter* reporter, bool checksum, |
| uint64_t initial_offset); |
| |
| ~Reader(); |
| |
| // Read the next record into *record. Returns true if read |
| // successfully, false if we hit end of the input. May use |
| // "*scratch" as temporary storage. The contents filled in *record |
| // will only be valid until the next mutating operation on this |
| // reader or the next mutation to *scratch. |
| bool ReadRecord(Slice* record, std::string* scratch); |
| |
| // Returns the physical offset of the last record returned by ReadRecord. |
| // |
| // Undefined before the first call to ReadRecord. |
| uint64_t LastRecordOffset(); |
| |
| private: |
| SequentialFile* const file_; |
| Reporter* const reporter_; |
| bool const checksum_; |
| char* const backing_store_; |
| Slice buffer_; |
| bool eof_; // Last Read() indicated EOF by returning < kBlockSize |
| |
| // Offset of the last record returned by ReadRecord. |
| uint64_t last_record_offset_; |
| // Offset of the first location past the end of buffer_. |
| uint64_t end_of_buffer_offset_; |
| |
| // Offset at which to start looking for the first record to return |
| uint64_t const initial_offset_; |
| |
| // Extend record types with the following special values |
| enum { |
| kEof = kMaxRecordType + 1, |
| // Returned whenever we find an invalid physical record. |
| // Currently there are three situations in which this happens: |
| // * The record has an invalid CRC (ReadPhysicalRecord reports a drop) |
| // * The record is a 0-length record (No drop is reported) |
| // * The record is below constructor's initial_offset (No drop is reported) |
| kBadRecord = kMaxRecordType + 2 |
| }; |
| |
| // Skips all blocks that are completely before "initial_offset_". |
| // |
| // Returns true on success. Handles reporting. |
| bool SkipToInitialBlock(); |
| |
| // Return type, or one of the preceding special values |
| unsigned int ReadPhysicalRecord(Slice* result); |
| |
| // Reports dropped bytes to the reporter. |
| // buffer_ must be updated to remove the dropped bytes prior to invocation. |
| void ReportCorruption(uint64_t bytes, const char* reason); |
| void ReportDrop(uint64_t bytes, const Status& reason); |
| |
| // No copying allowed |
| Reader(const Reader&); |
| void operator=(const Reader&); |
| }; |
| |
| } // namespace log |
| } // namespace leveldb |
| |
| #endif // STORAGE_LEVELDB_DB_LOG_READER_H_ |