1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
|
// Copyright (c) 2011-present, Facebook, Inc. All rights reserved.
// This source code is licensed under both the GPLv2 (found in the
// COPYING file in the root directory) and Apache 2.0 License
// (found in the LICENSE.Apache file in the root directory).
//
#pragma once
#ifndef ROCKSDB_LITE
#include <memory>
#include <string>
#include "file/random_access_file_reader.h"
#include "rocksdb/env.h"
#include "rocksdb/slice.h"
#include "rocksdb/statistics.h"
#include "rocksdb/status.h"
#include "utilities/blob_db/blob_log_format.h"
namespace ROCKSDB_NAMESPACE {
class SequentialFileReader;
class Logger;
namespace blob_db {
/**
* Reader is a general purpose log stream reader implementation. The actual job
* of reading from the device is implemented by the SequentialFile interface.
*
* Please see Writer for details on the file and record layout.
*/
class Reader {
public:
enum ReadLevel {
kReadHeader,
kReadHeaderKey,
kReadHeaderKeyBlob,
};
// Create a reader that will return log records from "*file".
// "*file" must remain live while this Reader is in use.
Reader(std::unique_ptr<RandomAccessFileReader>&& file_reader, Env* env,
Statistics* statistics);
// No copying allowed
Reader(const Reader&) = delete;
Reader& operator=(const Reader&) = delete;
~Reader() = default;
Status ReadHeader(BlobLogHeader* header);
// 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.
// If blob_offset is non-null, return offset of the blob through it.
Status ReadRecord(BlobLogRecord* record, ReadLevel level = kReadHeader,
uint64_t* blob_offset = nullptr);
void ResetNextByte() { next_byte_ = 0; }
uint64_t GetNextByte() const { return next_byte_; }
private:
Status ReadSlice(uint64_t size, Slice* slice, char* buf);
const std::unique_ptr<RandomAccessFileReader> file_;
Env* env_;
Statistics* statistics_;
Slice buffer_;
char header_buf_[BlobLogRecord::kHeaderSize];
// which byte to read next. For asserting proper usage
uint64_t next_byte_;
};
} // namespace blob_db
} // namespace ROCKSDB_NAMESPACE
#endif // ROCKSDB_LITE
|
