1  // Copyright (c) 2011 The LevelDB Authors. All rights reserved.
 2  // Use of this source code is governed by a BSD-style license that can be
 3  // found in the LICENSE file. See the AUTHORS file for names of contributors.
 4  
 5  #ifndef STORAGE_LEVELDB_DB_LOG_WRITER_H_
 6  #define STORAGE_LEVELDB_DB_LOG_WRITER_H_
 7  
 8  #include <stdint.h>
 9  
10  #include "db/log_format.h"
11  #include "leveldb/slice.h"
12  #include "leveldb/status.h"
13  
14  namespace leveldb {
15  
16  class WritableFile;
17  
18  namespace log {
19  
20  class Writer {
21   public:
22    // Create a writer that will append data to "*dest".
23    // "*dest" must be initially empty.
24    // "*dest" must remain live while this Writer is in use.
25    explicit Writer(WritableFile* dest);
26  
27    // Create a writer that will append data to "*dest".
28    // "*dest" must have initial length "dest_length".
29    // "*dest" must remain live while this Writer is in use.
30    Writer(WritableFile* dest, uint64_t dest_length);
31  
32    Writer(const Writer&) = delete;
33    Writer& operator=(const Writer&) = delete;
34  
35    ~Writer();
36  
37    Status AddRecord(const Slice& slice);
38  
39   private:
40    Status EmitPhysicalRecord(RecordType type, const char* ptr, size_t length);
41  
42    WritableFile* dest_;
43    int block_offset_;  // Current offset in block
44  
45    // crc32c values for all supported record types.  These are
46    // pre-computed to reduce the overhead of computing the crc of the
47    // record type stored in the header.
48    uint32_t type_crc_[kMaxRecordType + 1];
49  };
50  
51  }  // namespace log
52  }  // namespace leveldb
53  
54  #endif  // STORAGE_LEVELDB_DB_LOG_WRITER_H_