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
|
#ifndef UTIL_PROBING_HASH_TABLE__
#define UTIL_PROBING_HASH_TABLE__
#include "util/exception.hh"
#include <algorithm>
#include <cstddef>
#include <functional>
#include <assert.h>
namespace util {
/* Thrown when table grows too large */
class ProbingSizeException : public Exception {
public:
ProbingSizeException() throw() {}
~ProbingSizeException() throw() {}
};
// std::identity is an SGI extension :-(
struct IdentityHash {
template <class T> T operator()(T arg) const { return arg; }
};
/* Non-standard hash table
* Buckets must be set at the beginning and must be greater than maximum number
* of elements, else it throws ProbingSizeException.
* Memory management and initialization is externalized to make it easier to
* serialize these to disk and load them quickly.
* Uses linear probing to find value.
* Only insert and lookup operations.
*/
template <class EntryT, class HashT, class EqualT = std::equal_to<typename EntryT::Key> > class ProbingHashTable {
public:
typedef EntryT Entry;
typedef typename Entry::Key Key;
typedef const Entry *ConstIterator;
typedef Entry *MutableIterator;
typedef HashT Hash;
typedef EqualT Equal;
public:
static std::size_t Size(std::size_t entries, float multiplier) {
std::size_t buckets = std::max(entries + 1, static_cast<std::size_t>(multiplier * static_cast<float>(entries)));
return buckets * sizeof(Entry);
}
// Must be assigned to later.
ProbingHashTable() : entries_(0)
#ifdef DEBUG
, initialized_(false)
#endif
{}
ProbingHashTable(void *start, std::size_t allocated, const Key &invalid = Key(), const Hash &hash_func = Hash(), const Equal &equal_func = Equal())
: begin_(reinterpret_cast<MutableIterator>(start)),
buckets_(allocated / sizeof(Entry)),
end_(begin_ + buckets_),
invalid_(invalid),
hash_(hash_func),
equal_(equal_func),
entries_(0)
#ifdef DEBUG
, initialized_(true)
#endif
{}
template <class T> MutableIterator Insert(const T &t) {
#ifdef DEBUG
assert(initialized_);
#endif
UTIL_THROW_IF(++entries_ >= buckets_, ProbingSizeException, "Hash table with " << buckets_ << " buckets is full.");
for (MutableIterator i(begin_ + (hash_(t.GetKey()) % buckets_));;) {
if (equal_(i->GetKey(), invalid_)) { *i = t; return i; }
if (++i == end_) { i = begin_; }
}
}
// Return true if the value was found (and not inserted). This is consistent with Find but the opposite if hash_map!
template <class T> bool FindOrInsert(const T &t, MutableIterator &out) {
#ifdef DEBUG
assert(initialized_);
#endif
for (MutableIterator i(begin_ + (hash_(t.GetKey()) % buckets_));;) {
Key got(i->GetKey());
if (equal_(got, t.GetKey())) { out = i; return true; }
if (equal_(got, invalid_)) {
UTIL_THROW_IF(++entries_ >= buckets_, ProbingSizeException, "Hash table with " << buckets_ << " buckets is full.");
*i = t;
out = i;
return false;
}
if (++i == end_) i = begin_;
}
}
void FinishedInserting() {}
void LoadedBinary() {}
// Don't change anything related to GetKey,
template <class Key> bool UnsafeMutableFind(const Key key, MutableIterator &out) {
#ifdef DEBUG
assert(initialized_);
#endif
for (MutableIterator i(begin_ + (hash_(key) % buckets_));;) {
Key got(i->GetKey());
if (equal_(got, key)) { out = i; return true; }
if (equal_(got, invalid_)) return false;
if (++i == end_) i = begin_;
}
}
template <class Key> bool Find(const Key key, ConstIterator &out) const {
#ifdef DEBUG
assert(initialized_);
#endif
for (ConstIterator i(begin_ + (hash_(key) % buckets_));;) {
Key got(i->GetKey());
if (equal_(got, key)) { out = i; return true; }
if (equal_(got, invalid_)) return false;
if (++i == end_) i = begin_;
}
}
private:
MutableIterator begin_;
std::size_t buckets_;
MutableIterator end_;
Key invalid_;
Hash hash_;
Equal equal_;
std::size_t entries_;
#ifdef DEBUG
bool initialized_;
#endif
};
} // namespace util
#endif // UTIL_PROBING_HASH_TABLE__
|
