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
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
|
/* SPDX-License-Identifier: LGPL-2.1-or-later */
/*
* Priority Queue
* The prioq object implements a priority queue. That is, it orders objects by
* their priority and allows O(1) access to the object with the highest
* priority. Insertion and removal are Θ(log n). Optionally, the caller can
* provide a pointer to an index which will be kept up-to-date by the prioq.
*
* The underlying algorithm used in this implementation is a Heap.
*/
#include <errno.h>
#include <stdlib.h>
#include "alloc-util.h"
#include "hashmap.h"
#include "prioq.h"
struct prioq_item {
void *data;
unsigned *idx;
};
struct Prioq {
compare_func_t compare_func;
unsigned n_items, n_allocated;
struct prioq_item *items;
};
Prioq *prioq_new(compare_func_t compare_func) {
Prioq *q;
q = new(Prioq, 1);
if (!q)
return q;
*q = (Prioq) {
.compare_func = compare_func,
};
return q;
}
Prioq* prioq_free(Prioq *q) {
if (!q)
return NULL;
free(q->items);
return mfree(q);
}
int prioq_ensure_allocated(Prioq **q, compare_func_t compare_func) {
assert(q);
if (*q)
return 0;
*q = prioq_new(compare_func);
if (!*q)
return -ENOMEM;
return 0;
}
static void swap(Prioq *q, unsigned j, unsigned k) {
assert(q);
assert(j < q->n_items);
assert(k < q->n_items);
assert(!q->items[j].idx || *(q->items[j].idx) == j);
assert(!q->items[k].idx || *(q->items[k].idx) == k);
SWAP_TWO(q->items[j].data, q->items[k].data);
SWAP_TWO(q->items[j].idx, q->items[k].idx);
if (q->items[j].idx)
*q->items[j].idx = j;
if (q->items[k].idx)
*q->items[k].idx = k;
}
static unsigned shuffle_up(Prioq *q, unsigned idx) {
assert(q);
assert(idx < q->n_items);
while (idx > 0) {
unsigned k;
k = (idx-1)/2;
if (q->compare_func(q->items[k].data, q->items[idx].data) <= 0)
break;
swap(q, idx, k);
idx = k;
}
return idx;
}
static unsigned shuffle_down(Prioq *q, unsigned idx) {
assert(q);
for (;;) {
unsigned j, k, s;
k = (idx+1)*2; /* right child */
j = k-1; /* left child */
if (j >= q->n_items)
break;
if (q->compare_func(q->items[j].data, q->items[idx].data) < 0)
/* So our left child is smaller than we are, let's
* remember this fact */
s = j;
else
s = idx;
if (k < q->n_items &&
q->compare_func(q->items[k].data, q->items[s].data) < 0)
/* So our right child is smaller than we are, let's
* remember this fact */
s = k;
/* s now points to the smallest of the three items */
if (s == idx)
/* No swap necessary, we're done */
break;
swap(q, idx, s);
idx = s;
}
return idx;
}
int prioq_put(Prioq *q, void *data, unsigned *idx) {
struct prioq_item *i;
unsigned k;
assert(q);
if (q->n_items >= q->n_allocated) {
unsigned n;
struct prioq_item *j;
n = MAX((q->n_items+1) * 2, 16u);
j = reallocarray(q->items, n, sizeof(struct prioq_item));
if (!j)
return -ENOMEM;
q->items = j;
q->n_allocated = n;
}
k = q->n_items++;
i = q->items + k;
i->data = data;
i->idx = idx;
if (idx)
*idx = k;
shuffle_up(q, k);
return 0;
}
static void remove_item(Prioq *q, struct prioq_item *i) {
struct prioq_item *l;
assert(q);
assert(i);
l = q->items + q->n_items - 1;
if (i == l)
/* Last entry, let's just remove it */
q->n_items--;
else {
unsigned k;
/* Not last entry, let's replace the last entry with
* this one, and reshuffle */
k = i - q->items;
i->data = l->data;
i->idx = l->idx;
if (i->idx)
*i->idx = k;
q->n_items--;
k = shuffle_down(q, k);
shuffle_up(q, k);
}
}
_pure_ static struct prioq_item* find_item(Prioq *q, void *data, unsigned *idx) {
struct prioq_item *i;
assert(q);
if (q->n_items <= 0)
return NULL;
if (idx) {
if (*idx == PRIOQ_IDX_NULL ||
*idx >= q->n_items)
return NULL;
i = q->items + *idx;
if (i->data != data)
return NULL;
return i;
} else {
for (i = q->items; i < q->items + q->n_items; i++)
if (i->data == data)
return i;
return NULL;
}
}
int prioq_remove(Prioq *q, void *data, unsigned *idx) {
struct prioq_item *i;
if (!q)
return 0;
i = find_item(q, data, idx);
if (!i)
return 0;
remove_item(q, i);
return 1;
}
int prioq_reshuffle(Prioq *q, void *data, unsigned *idx) {
struct prioq_item *i;
unsigned k;
assert(q);
i = find_item(q, data, idx);
if (!i)
return 0;
k = i - q->items;
k = shuffle_down(q, k);
shuffle_up(q, k);
return 1;
}
void *prioq_peek_by_index(Prioq *q, unsigned idx) {
if (!q)
return NULL;
if (idx >= q->n_items)
return NULL;
return q->items[idx].data;
}
void *prioq_pop(Prioq *q) {
void *data;
if (!q)
return NULL;
if (q->n_items <= 0)
return NULL;
data = q->items[0].data;
remove_item(q, q->items);
return data;
}
unsigned prioq_size(Prioq *q) {
if (!q)
return 0;
return q->n_items;
}
bool prioq_isempty(Prioq *q) {
if (!q)
return true;
return q->n_items <= 0;
}
|
