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
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
|
// 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_FORMAT_H_
#define STORAGE_LEVELDB_DB_FORMAT_H_
#include <stdio.h>
#include "leveldb/comparator.h"
#include "leveldb/db.h"
#include "leveldb/slice.h"
#include "leveldb/table_builder.h"
#include "util/coding.h"
#include "util/logging.h"
namespace leveldb {
// Grouping of constants. We may want to make some of these
// parameters set via options.
namespace config {
static const int kNumLevels = 7;
}
class InternalKey;
// Value types encoded as the last component of internal keys.
// DO NOT CHANGE THESE ENUM VALUES: they are embedded in the on-disk
// data structures.
enum ValueType {
kTypeDeletion = 0x0,
kTypeValue = 0x1,
kTypeLargeValueRef = 0x2,
};
// kValueTypeForSeek defines the ValueType that should be passed when
// constructing a ParsedInternalKey object for seeking to a particular
// sequence number (since we sort sequence numbers in decreasing order
// and the value type is embedded as the low 8 bits in the sequence
// number in internal keys, we need to use the highest-numbered
// ValueType, not the lowest).
static const ValueType kValueTypeForSeek = kTypeLargeValueRef;
typedef uint64_t SequenceNumber;
// We leave eight bits empty at the bottom so a type and sequence#
// can be packed together into 64-bits.
static const SequenceNumber kMaxSequenceNumber =
((0x1ull << 56) - 1);
struct ParsedInternalKey {
Slice user_key;
SequenceNumber sequence;
ValueType type;
ParsedInternalKey() { } // Intentionally left uninitialized (for speed)
ParsedInternalKey(const Slice& u, const SequenceNumber& seq, ValueType t)
: user_key(u), sequence(seq), type(t) { }
std::string DebugString() const;
};
// Return the length of the encoding of "key".
inline size_t InternalKeyEncodingLength(const ParsedInternalKey& key) {
return key.user_key.size() + 8;
}
// Append the serialization of "key" to *result.
extern void AppendInternalKey(std::string* result,
const ParsedInternalKey& key);
// Attempt to parse an internal key from "internal_key". On success,
// stores the parsed data in "*result", and returns true.
//
// On error, returns false, leaves "*result" in an undefined state.
extern bool ParseInternalKey(const Slice& internal_key,
ParsedInternalKey* result);
// Returns the user key portion of an internal key.
inline Slice ExtractUserKey(const Slice& internal_key) {
assert(internal_key.size() >= 8);
return Slice(internal_key.data(), internal_key.size() - 8);
}
inline ValueType ExtractValueType(const Slice& internal_key) {
assert(internal_key.size() >= 8);
const size_t n = internal_key.size();
uint64_t num = DecodeFixed64(internal_key.data() + n - 8);
unsigned char c = num & 0xff;
return static_cast<ValueType>(c);
}
// A comparator for internal keys that uses a specified comparator for
// the user key portion and breaks ties by decreasing sequence number.
class InternalKeyComparator : public Comparator {
private:
const Comparator* user_comparator_;
public:
explicit InternalKeyComparator(const Comparator* c) : user_comparator_(c) { }
virtual const char* Name() const;
virtual int Compare(const Slice& a, const Slice& b) const;
virtual void FindShortestSeparator(
std::string* start,
const Slice& limit) const;
virtual void FindShortSuccessor(std::string* key) const;
const Comparator* user_comparator() const { return user_comparator_; }
int Compare(const InternalKey& a, const InternalKey& b) const;
};
// Modules in this directory should keep internal keys wrapped inside
// the following class instead of plain strings so that we do not
// incorrectly use string comparisons instead of an InternalKeyComparator.
class InternalKey {
private:
std::string rep_;
public:
InternalKey() { } // Leave rep_ as empty to indicate it is invalid
InternalKey(const Slice& user_key, SequenceNumber s, ValueType t) {
AppendInternalKey(&rep_, ParsedInternalKey(user_key, s, t));
}
void DecodeFrom(const Slice& s) { rep_.assign(s.data(), s.size()); }
Slice Encode() const {
assert(!rep_.empty());
return rep_;
}
Slice user_key() const { return ExtractUserKey(rep_); }
void SetFrom(const ParsedInternalKey& p) {
rep_.clear();
AppendInternalKey(&rep_, p);
}
void Clear() { rep_.clear(); }
};
inline int InternalKeyComparator::Compare(
const InternalKey& a, const InternalKey& b) const {
return Compare(a.Encode(), b.Encode());
}
// LargeValueRef is a 160-bit hash value (20 bytes), plus an 8 byte
// uncompressed size, and a 1 byte CompressionType code. An
// encoded form of it is embedded in the filenames of large value
// files stored in the database, and the raw binary form is stored as
// the iter->value() result for values of type kTypeLargeValueRef in
// the table and log files that make up the database.
struct LargeValueRef {
char data[29];
// Initialize a large value ref for the given data
static LargeValueRef Make(const Slice& data,
CompressionType compression_type);
// Initialize a large value ref from a serialized, 29-byte reference value
static LargeValueRef FromRef(const Slice& ref) {
LargeValueRef result;
assert(ref.size() == sizeof(result.data));
memcpy(result.data, ref.data(), sizeof(result.data));
return result;
}
// Return the number of bytes in a LargeValueRef (not the
// number of bytes in the value referenced).
static size_t ByteSize() { return sizeof(LargeValueRef().data); }
// Return the number of bytes in the value referenced by "*this".
uint64_t ValueSize() const { return DecodeFixed64(&data[20]); }
CompressionType compression_type() const {
return static_cast<CompressionType>(data[28]);
}
bool operator==(const LargeValueRef& b) const {
return memcmp(data, b.data, sizeof(data)) == 0;
}
bool operator<(const LargeValueRef& b) const {
return memcmp(data, b.data, sizeof(data)) < 0;
}
};
// Convert the large value ref to a human-readable string suitable
// for embedding in a large value filename.
extern std::string LargeValueRefToFilenameString(const LargeValueRef& h);
// Parse the large value filename string in "input" and store it in
// "*h". If successful, returns true. Otherwise returns false.
extern bool FilenameStringToLargeValueRef(const Slice& in, LargeValueRef* ref);
inline bool ParseInternalKey(const Slice& internal_key,
ParsedInternalKey* result) {
const size_t n = internal_key.size();
if (n < 8) return false;
uint64_t num = DecodeFixed64(internal_key.data() + n - 8);
unsigned char c = num & 0xff;
result->sequence = num >> 8;
result->type = static_cast<ValueType>(c);
result->user_key = Slice(internal_key.data(), n - 8);
return (c <= static_cast<unsigned char>(kTypeLargeValueRef));
}
}
#endif // STORAGE_LEVELDB_DB_FORMAT_H_
|
