/usr/include/mongo/util/hashtab.h is in mongodb-dev 1:2.4.9-1ubuntu2.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
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 | /* 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.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#pragma once
#include "mongo/pch.h"
#include <map>
#include "../db/dur.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(const Key& k) {
bool found;
int i = _find(k, found);
if ( i >= 0 && found ) {
Node* n = &nodes(i);
n = getDur().writing(n);
n->k.kill();
n->setUnused();
}
}
/** returns false if too full */
bool put(const Key& k, const Type& value) {
bool found;
int i = _find(k, found);
if ( i < 0 )
return false;
Node* n = getDur().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
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