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
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
|
//===- HashBase.tcc -------------------------------------------------------===//
//
// The MCLinker Project
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//===--------------------------------------------------------------------===//
// internal non-member functions
inline static unsigned int compute_bucket_count(unsigned int pNumOfBuckets)
{
static const unsigned int bucket_size[] =
{
1, 3, 17, 37, 67, 97, 197, 419, 977, 2593, 4099, 8209, 12289,
16411, 20483, 32771, 49157, 65537, 98317, 131101, 196613
};
const unsigned int buckets_count =
sizeof(bucket_size) / sizeof(bucket_size[0]);
unsigned int idx = 0;
do {
if (pNumOfBuckets < bucket_size[idx]) {
return bucket_size[idx];
}
++idx;
} while(idx < buckets_count);
return (pNumOfBuckets+131101); // rare case. increase constantly
}
//===--------------------------------------------------------------------===//
// template implementation of HashBucket
template<typename DataType>
typename HashBucket<DataType>::entry_type*
HashBucket<DataType>::getEmptyBucket()
{
static entry_type* empty_bucket = reinterpret_cast<entry_type*>(0x0);
return empty_bucket;
}
template<typename DataType>
typename HashBucket<DataType>::entry_type*
HashBucket<DataType>::getTombstone()
{
static entry_type* tombstone = reinterpret_cast<entry_type*>(0x1);
return tombstone;
}
//===--------------------------------------------------------------------===//
// template implementation of HashTableImpl
template<typename HashEntryTy,
typename HashFunctionTy>
HashTableImpl<HashEntryTy, HashFunctionTy>::HashTableImpl()
: m_Buckets(0),
m_NumOfBuckets(0),
m_NumOfEntries(0),
m_NumOfTombstones(0),
m_Hasher() {
}
template<typename HashEntryTy,
typename HashFunctionTy>
HashTableImpl<HashEntryTy, HashFunctionTy>::HashTableImpl(
unsigned int pInitSize)
: m_Hasher() {
if (pInitSize) {
init(pInitSize);
return;
}
m_Buckets = 0;
m_NumOfBuckets = 0;
m_NumOfEntries = 0;
m_NumOfTombstones = 0;
}
template<typename HashEntryTy,
typename HashFunctionTy>
HashTableImpl<HashEntryTy, HashFunctionTy>::~HashTableImpl()
{
free(m_Buckets);
}
/// empty - check if the hash table is empty
template<typename HashEntryTy,
typename HashFunctionTy>
bool HashTableImpl<HashEntryTy, HashFunctionTy>::empty() const
{
return (0 == m_NumOfEntries);
}
/// init - initialize the hash table.
template<typename HashEntryTy,
typename HashFunctionTy>
void HashTableImpl<HashEntryTy, HashFunctionTy>::init(unsigned int pInitSize)
{
m_NumOfBuckets = pInitSize? compute_bucket_count(pInitSize): NumOfInitBuckets;
m_NumOfEntries = 0;
m_NumOfTombstones = 0;
/** calloc also set bucket.Item = bucket_type::getEmptyStone() **/
m_Buckets = (bucket_type*)calloc(m_NumOfBuckets, sizeof(bucket_type));
}
/// lookUpBucketFor - look up the bucket whose key is pKey
template<typename HashEntryTy,
typename HashFunctionTy>
unsigned int
HashTableImpl<HashEntryTy, HashFunctionTy>::lookUpBucketFor(
const typename HashTableImpl<HashEntryTy, HashFunctionTy>::key_type& pKey)
{
if (0 == m_NumOfBuckets) {
// NumOfBuckets is changed after init(pInitSize)
init(NumOfInitBuckets);
}
unsigned int full_hash = m_Hasher(pKey);
unsigned int index = full_hash % m_NumOfBuckets;
const unsigned int probe = 1;
int firstTombstone = -1;
// linear probing
while(true) {
bucket_type& bucket = m_Buckets[index];
// If we found an empty bucket, this key isn't in the table yet, return it.
if (bucket_type::getEmptyBucket() == bucket.Entry) {
if (-1 != firstTombstone) {
m_Buckets[firstTombstone].FullHashValue = full_hash;
return firstTombstone;
}
bucket.FullHashValue = full_hash;
return index;
}
if (bucket_type::getTombstone() == bucket.Entry) {
if (-1 == firstTombstone) {
firstTombstone = index;
}
}
else if (bucket.FullHashValue == full_hash) {
if (bucket.Entry->compare(pKey)) {
return index;
}
}
index += probe;
if (index == m_NumOfBuckets)
index = 0;
}
}
template<typename HashEntryTy,
typename HashFunctionTy>
int
HashTableImpl<HashEntryTy, HashFunctionTy>::findKey(
const typename HashTableImpl<HashEntryTy, HashFunctionTy>::key_type& pKey) const
{
if (0 == m_NumOfBuckets)
return -1;
unsigned int full_hash = m_Hasher(pKey);
unsigned int index = full_hash % m_NumOfBuckets;
const unsigned int probe = 1;
// linear probing
while (true) {
bucket_type &bucket = m_Buckets[index];
if (bucket_type::getEmptyBucket() == bucket.Entry)
return -1;
if (bucket_type::getTombstone() == bucket.Entry) {
// Ignore tombstones.
}
else if (full_hash == bucket.FullHashValue) {
// get string, compare, if match, return index
if (bucket.Entry->compare(pKey))
return index;
}
index += probe;
if (index == m_NumOfBuckets)
index = 0;
}
}
template<typename HashEntryTy,
typename HashFunctionTy>
void HashTableImpl<HashEntryTy, HashFunctionTy>::mayRehash()
{
unsigned int new_size;
// If the hash table is now more than 3/4 full, or if fewer than 1/8 of
// the buckets are empty (meaning that many are filled with tombstones),
// grow/rehash the table.
if ((m_NumOfEntries<<2) > m_NumOfBuckets*3)
new_size = compute_bucket_count(m_NumOfBuckets);
else if (((m_NumOfBuckets-(m_NumOfEntries+m_NumOfTombstones))<<3) < m_NumOfBuckets)
new_size = m_NumOfBuckets;
else
return;
doRehash(new_size);
}
template<typename HashEntryTy,
typename HashFunctionTy>
void HashTableImpl<HashEntryTy, HashFunctionTy>::doRehash(unsigned int pNewSize)
{
bucket_type* new_table = (bucket_type*)calloc(pNewSize, sizeof(bucket_type));
// Rehash all the items into their new buckets. Luckily :) we already have
// the hash values available, so we don't have to recall hash function again.
for (bucket_type *IB = m_Buckets, *E = m_Buckets+m_NumOfBuckets; IB != E; ++IB) {
if (IB->Entry != bucket_type::getEmptyBucket() &&
IB->Entry != bucket_type::getTombstone()) {
// Fast case, bucket available.
unsigned full_hash = IB->FullHashValue;
unsigned new_bucket = full_hash % pNewSize;
if (bucket_type::getEmptyBucket() == new_table[new_bucket].Entry) {
new_table[new_bucket].Entry = IB->Entry;
new_table[new_bucket].FullHashValue = full_hash;
continue;
}
// Otherwise probe for a spot.
const unsigned int probe = 1;
do {
new_bucket += probe;
if (new_bucket == pNewSize)
new_bucket = 0;
} while (new_table[new_bucket].Entry != bucket_type::getEmptyBucket());
// Finally found a slot. Fill it in.
new_table[new_bucket].Entry = IB->Entry;
new_table[new_bucket].FullHashValue = full_hash;
}
}
free(m_Buckets);
m_Buckets = new_table;
m_NumOfBuckets = pNewSize;
m_NumOfTombstones = 0;
}
|
