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// 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 "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.
Reader(SequentialFile* file, Reporter* reporter, bool checksum);
~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);
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
// Extend record types with the following special values
enum {
kEof = kMaxRecordType + 1,
kBadRecord = kMaxRecordType + 2
};
// Return type, or one of the preceding special values
unsigned int ReadPhysicalRecord(Slice* result);
void ReportDrop(size_t bytes, const char* reason);
// No copying allowed
Reader(const Reader&);
void operator=(const Reader&);
};
}
}
#endif // STORAGE_LEVELDB_DB_LOG_READER_H_
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