- // 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(size_t bytes, const char* reason);
- void ReportDrop(size_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_
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