mirror of
https://github.com/mongodb/mongo.git
synced 2024-11-30 17:10:48 +01:00
132 lines
3.2 KiB
C++
132 lines
3.2 KiB
C++
/**
|
|
* Copyright (C) 2008 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/>.
|
|
*/
|
|
|
|
/* 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.
|
|
*/
|
|
|
|
#pragma once
|
|
|
|
#include "../stdafx.h"
|
|
#include <map>
|
|
|
|
#pragma pack(push,1)
|
|
|
|
/* you should define:
|
|
|
|
int Key::hash() return > 0 always.
|
|
*/
|
|
|
|
template <
|
|
class Key,
|
|
class Type
|
|
>
|
|
class HashTable {
|
|
public:
|
|
const char *name;
|
|
struct Node {
|
|
int hash;
|
|
Key k;
|
|
Type value;
|
|
bool inUse() {
|
|
return hash != 0;
|
|
}
|
|
void setUnused() {
|
|
hash = 0;
|
|
}
|
|
} *nodes;
|
|
int n;
|
|
|
|
int _find(const Key& k, bool& found) {
|
|
found = false;
|
|
int h = k.hash();
|
|
int i = h % n;
|
|
int start = i;
|
|
int chain = 0;
|
|
while ( 1 ) {
|
|
if ( !nodes[i].inUse() ) {
|
|
return i;
|
|
}
|
|
if ( nodes[i].hash == h && nodes[i].k == k ) {
|
|
found = true;
|
|
return i;
|
|
}
|
|
chain++;
|
|
i = (i+1) % n;
|
|
if ( i == start ) {
|
|
cout << "warning: hashtable is full " << name << endl;
|
|
return -1;
|
|
}
|
|
if ( chain == 200 )
|
|
cout << "warning: hashtable long chain " << name << endl;
|
|
}
|
|
}
|
|
|
|
public:
|
|
/* buf must be all zeroes on initialization. */
|
|
HashTable(void *buf, int buflen, const char *_name) : name(_name) {
|
|
int m = sizeof(Node);
|
|
// cout << "hashtab init, buflen:" << buflen << " m:" << m << endl;
|
|
n = buflen / m;
|
|
if ( (n & 1) == 0 )
|
|
n--;
|
|
nodes = (Node *) buf;
|
|
assert(nodes[n-1].hash == 0);
|
|
assert(nodes[0].hash == 0);
|
|
|
|
assert( sizeof(Node) == 628 );
|
|
//cout << "HashTable() " << _name << " sizeof(node):" << sizeof(Node) << " n:" << n << endl;
|
|
}
|
|
|
|
Type* get(const Key& k) {
|
|
bool found;
|
|
int i = _find(k, found);
|
|
if ( found )
|
|
return &nodes[i].value;
|
|
return 0;
|
|
}
|
|
|
|
void kill(const Key& k) {
|
|
bool found;
|
|
int i = _find(k, found);
|
|
if ( i >= 0 && found ) {
|
|
nodes[i].k.kill();
|
|
nodes[i].setUnused();
|
|
}
|
|
}
|
|
|
|
void put(const Key& k, const Type& value) {
|
|
bool found;
|
|
int i = _find(k, found);
|
|
if ( i < 0 )
|
|
return;
|
|
if ( !found ) {
|
|
nodes[i].k = k;
|
|
nodes[i].hash = k.hash();
|
|
}
|
|
else {
|
|
assert( nodes[i].hash == k.hash() );
|
|
}
|
|
nodes[i].value = value;
|
|
}
|
|
|
|
};
|
|
|
|
#pragma pack(pop)
|