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
|
/**
* Hashmap implementation.
*/
type hashfn<K> = fn(&K) -> uint;
type eqfn<K> = fn(&K, &K) -> bool;
type hashmap<K, V> =
obj {
fn size() -> uint;
fn insert(&K, &V) -> bool;
fn contains_key(&K) -> bool;
fn get(&K) -> V;
fn find(&K) -> option::t<V>;
fn remove(&K) -> option::t<V>;
fn rehash();
iter items() -> @{key: K, val: V};
iter keys() -> K;
};
type hashset<K> = hashmap<K, ()>;
fn set_add<@K>(set: hashset<K>, key: &K) -> bool { ret set.insert(key, ()); }
fn mk_hashmap<@K, @V>(hasher: &hashfn<K>, eqer: &eqfn<K>) -> hashmap<K, V> {
let initial_capacity: uint = 32u; // 2^5
let load_factor: util::rational = {num: 3, den: 4};
tag bucket<@K, @V> { nil; deleted; some(K, V); }
fn make_buckets<@K, @V>(nbkts: uint) -> [mutable bucket<K, V>] {
ret vec::init_elt_mut::<bucket<K, V>>(nil::<K, V>, nbkts);
}
// Derive two hash functions from the one given by taking the upper
// half and lower half of the uint bits. Our bucket probing
// sequence is then defined by
//
// hash(key, i) := hashl(key) * i + hashr(key) for i = 0, 1, 2, ...
//
// Tearing the hash function apart this way is kosher in practice
// as, assuming 32-bit uints, the table would have to be at 2^32
// buckets before the resulting pair of hash functions no longer
// probes all buckets for a fixed key. Note that hashl is made to
// output odd numbers (hence coprime to the number of nbkts, which
// is always a power of 2), so that all buckets are probed for a
// fixed key.
fn hashl(n: uint, _nbkts: uint) -> uint { ret (n >>> 16u) * 2u + 1u; }
fn hashr(n: uint, _nbkts: uint) -> uint { ret 0x0000_ffff_u & n; }
fn hash(h: uint, nbkts: uint, i: uint) -> uint {
ret (hashl(h, nbkts) * i + hashr(h, nbkts)) % nbkts;
}
/**
* We attempt to never call this with a full table. If we do, it
* will fail.
*/
fn insert_common<@K,
@V>(hasher: &hashfn<K>, eqer: &eqfn<K>,
bkts: &[mutable bucket<K, V>], nbkts: uint, key: &K,
val: &V) -> bool {
let i: uint = 0u;
let h: uint = hasher(key);
while i < nbkts {
let j: uint = hash(h, nbkts, i);
alt bkts[j] {
some(k, _) {
// Copy key to please alias analysis.
let k_ = k;
if eqer(key, k_) { bkts[j] = some(k_, val); ret false; }
i += 1u;
}
_ { bkts[j] = some(key, val); ret true; }
}
}
fail; // full table
}
fn find_common<@K,
@V>(hasher: &hashfn<K>, eqer: &eqfn<K>,
bkts: &[mutable bucket<K, V>], nbkts: uint, key: &K) ->
option::t<V> {
let i: uint = 0u;
let h: uint = hasher(key);
while i < nbkts {
let j: uint = hash(h, nbkts, i);
alt bkts[j] {
some(k, v) {
// Copy to please alias analysis.
let k_ = k;
let v_ = v;
if eqer(key, k_) { ret option::some(v_); }
}
nil. { ret option::none; }
deleted. { }
}
i += 1u;
}
ret option::none;
}
fn rehash<@K,
@V>(hasher: &hashfn<K>, eqer: &eqfn<K>,
oldbkts: &[mutable bucket<K, V>], _noldbkts: uint,
newbkts: &[mutable bucket<K, V>], nnewbkts: uint) {
for b: bucket<K, V> in oldbkts {
alt b {
some(k_, v_) {
let k = k_;
let v = v_;
insert_common(hasher, eqer, newbkts, nnewbkts, k, v);
}
_ { }
}
}
}
obj hashmap<@K,
@V>(hasher: hashfn<K>,
eqer: eqfn<K>,
mutable bkts: [mutable bucket<K, V>],
mutable nbkts: uint,
mutable nelts: uint,
lf: util::rational) {
fn size() -> uint { ret nelts; }
fn insert(key: &K, val: &V) -> bool {
let load: util::rational =
{num: nelts + 1u as int, den: nbkts as int};
if !util::rational_leq(load, lf) {
let nnewbkts: uint = uint::next_power_of_two(nbkts + 1u);
let newbkts = make_buckets(nnewbkts);
rehash(hasher, eqer, bkts, nbkts, newbkts, nnewbkts);
bkts = newbkts;
nbkts = nnewbkts;
}
if insert_common(hasher, eqer, bkts, nbkts, key, val) {
nelts += 1u;
ret true;
}
ret false;
}
fn contains_key(key: &K) -> bool {
ret alt find_common(hasher, eqer, bkts, nbkts, key) {
option::some(_) { true }
_ { false }
};
}
fn get(key: &K) -> V {
ret alt find_common(hasher, eqer, bkts, nbkts, key) {
option::some(val) { val }
_ { fail }
};
}
fn find(key: &K) -> option::t<V> {
be find_common(hasher, eqer, bkts, nbkts, key);
}
fn remove(key: &K) -> option::t<V> {
let i: uint = 0u;
let h: uint = hasher(key);
while i < nbkts {
let j: uint = hash(h, nbkts, i);
alt bkts[j] {
some(k, v) {
let k_ = k;
let vo = option::some(v);
if eqer(key, k_) {
bkts[j] = deleted;
nelts -= 1u;
ret vo;
}
}
deleted. { }
nil. { ret option::none; }
}
i += 1u;
}
ret option::none;
}
fn rehash() {
let newbkts = make_buckets(nbkts);
rehash(hasher, eqer, bkts, nbkts, newbkts, nbkts);
bkts = newbkts;
}
iter items() -> @{key: K, val: V} {
for b: bucket<K, V> in bkts {
alt b { some(k, v) { put @{key: k, val: v}; } _ { } }
}
}
iter keys() -> K {
for b: bucket<K, V> in bkts {
alt b { some(k, _) { put k; } _ { } }
}
}
}
let bkts = make_buckets(initial_capacity);
ret hashmap(hasher, eqer, bkts, initial_capacity, 0u, load_factor);
}
// Hash map constructors for basic types
fn new_str_hash<@V>() -> hashmap<istr, V> {
ret mk_hashmap(istr::hash, istr::eq);
}
fn new_int_hash<@V>() -> hashmap<int, V> {
fn hash_int(x: &int) -> uint { ret x as uint; }
fn eq_int(a: &int, b: &int) -> bool { ret a == b; }
ret mk_hashmap(hash_int, eq_int);
}
fn new_uint_hash<@V>() -> hashmap<uint, V> {
fn hash_uint(x: &uint) -> uint { ret x; }
fn eq_uint(a: &uint, b: &uint) -> bool { ret a == b; }
ret mk_hashmap(hash_uint, eq_uint);
}
// Local Variables:
// mode: rust;
// fill-column: 78;
// indent-tabs-mode: nil
// c-basic-offset: 4
// buffer-file-coding-system: utf-8-unix
// compile-command: "make -k -C $RBUILD 2>&1 | sed -e 's/\\/x\\//x:\\//g'";
// End:
|
