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
|
/* hashtab.h
Simple, fixed size hash table. Darn simple.
Uses a contiguous block of memory, so you can put it in a memory mapped file very easily.
*/
/* Copyright 2009 10gen Inc.
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License, version 3,
* as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
* As a special exception, the copyright holders give permission to link the
* code of portions of this program with the OpenSSL library under certain
* conditions as described in each individual source file and distribute
* linked combinations including the program with the OpenSSL library. You
* must comply with the GNU Affero General Public License in all respects
* for all of the code used other than as permitted herein. If you modify
* file(s) with this exception, you may extend this exception to your
* version of the file(s), but you are not obligated to do so. If you do not
* wish to do so, delete this exception statement from your version. If you
* delete this exception statement from all source files in the program,
* then also delete it in the license file.
*/
#pragma once
#include "mongo/pch.h"
#include <map>
#include "mongo/db/storage/mmap_v1/dur.h"
#include "mongo/db/operation_context.h"
namespace mongo {
#pragma pack(1)
/* you should define:
int Key::hash() return > 0 always.
*/
template <class Key,class Type>
class HashTable : boost::noncopyable {
public:
const char *name;
struct Node {
int hash;
Key k;
Type value;
bool inUse() {
return hash != 0;
}
void setUnused() {
hash = 0;
}
};
void* _buf;
int n; // number of hashtable buckets
int maxChain;
Node& nodes(int i) {
Node *nodes = (Node *) _buf;
return nodes[i];
}
int _find(const Key& k, bool& found) {
found = false;
int h = k.hash();
int i = h % n;
int start = i;
int chain = 0;
int firstNonUsed = -1;
while ( 1 ) {
if ( !nodes(i).inUse() ) {
if ( firstNonUsed < 0 )
firstNonUsed = i;
}
if ( nodes(i).hash == h && nodes(i).k == k ) {
if ( chain >= 200 )
out() << "warning: hashtable " << name << " long chain " << endl;
found = true;
return i;
}
chain++;
i = (i+1) % n;
if ( i == start ) {
// shouldn't get here / defensive for infinite loops
out() << "error: hashtable " << name << " is full n:" << n << endl;
return -1;
}
if( chain >= maxChain ) {
if ( firstNonUsed >= 0 )
return firstNonUsed;
out() << "error: hashtable " << name << " max chain reached:" << maxChain << endl;
return -1;
}
}
}
public:
/* buf must be all zeroes on initialization. */
HashTable(void* buf, int buflen, const char *_name) : name(_name) {
int m = sizeof(Node);
// out() << "hashtab init, buflen:" << buflen << " m:" << m << endl;
n = buflen / m;
if ( (n & 1) == 0 )
n--;
maxChain = (int) (n * 0.05);
_buf = buf;
//nodes = (Node *) buf;
if ( sizeof(Node) != 628 ) {
out() << "HashTable() " << _name << " sizeof(node):" << sizeof(Node) << " n:" << n << " sizeof(Key): " << sizeof(Key) << " sizeof(Type):" << sizeof(Type) << endl;
verify( sizeof(Node) == 628 );
}
}
Type* get(const Key& k) {
bool found;
int i = _find(k, found);
if ( found )
return &nodes(i).value;
return 0;
}
void kill(OperationContext* txn, const Key& k) {
bool found;
int i = _find(k, found);
if ( i >= 0 && found ) {
Node* n = &nodes(i);
n = txn->recoveryUnit()->writing(n);
n->k.kill();
n->setUnused();
}
}
/** returns false if too full */
bool put(OperationContext* txn, const Key& k, const Type& value) {
bool found;
int i = _find(k, found);
if ( i < 0 )
return false;
Node* n = txn->recoveryUnit()->writing( &nodes(i) );
if ( !found ) {
n->k = k;
n->hash = k.hash();
}
else {
verify( n->hash == k.hash() );
}
n->value = value;
return true;
}
typedef void (*IteratorCallback)( const Key& k , Type& v );
void iterAll( IteratorCallback callback ) {
for ( int i=0; i<n; i++ ) {
if ( nodes(i).inUse() ) {
callback( nodes(i).k , nodes(i).value );
}
}
}
// TODO: should probably use boost::bind for this, but didn't want to look at it
typedef void (*IteratorCallback2)( const Key& k , Type& v , void * extra );
void iterAll( IteratorCallback2 callback , void * extra ) {
for ( int i=0; i<n; i++ ) {
if ( nodes(i).inUse() ) {
callback( nodes(i).k , nodes(i).value , extra );
}
}
}
};
#pragma pack()
} // namespace mongo
|
