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shared: add simple priority queue implementation

keep-around/ba91431154ad7bac82ddf0a540ec1b40db62d782
Lennart Poettering 10 years ago
parent
commit
30bdd69525
  1. 1
      .gitignore
  2. 14
      Makefile.am
  3. 281
      src/shared/prioq.c
  4. 39
      src/shared/prioq.h
  5. 166
      src/test/test-prioq.c

1
.gitignore

@ -111,6 +111,7 @@
/test-loopback
/test-mmap-cache
/test-ns
/test-prioq
/test-replace-var
/test-sched-prio
/test-sleep

14
Makefile.am

@ -620,6 +620,8 @@ libsystemd_shared_la_SOURCES = \
src/shared/set.h \
src/shared/fdset.c \
src/shared/fdset.h \
src/shared/prioq.c \
src/shared/prioq.h \
src/shared/strv.c \
src/shared/strv.h \
src/shared/env-util.c \
@ -1075,7 +1077,8 @@ noinst_tests += \
test-sched-prio \
test-calendarspec \
test-strip-tab-ansi \
test-cgroup-util
test-cgroup-util \
test-prioq
EXTRA_DIST += \
test/sched_idle_bad.service \
@ -1166,6 +1169,15 @@ test_util_CFLAGS = \
test_util_LDADD = \
libsystemd-core.la
test_prioq_SOURCES = \
src/test/test-prioq.c
test_prioq_CFLAGS = \
$(AM_CFLAGS)
test_prioq_LDADD = \
libsystemd-core.la
test_log_SOURCES = \
src/test/test-log.c

281
src/shared/prioq.c

@ -0,0 +1,281 @@
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
/***
This file is part of systemd.
Copyright 2013 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include "util.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 = new0(Prioq, 1);
if (!q)
return q;
q->compare_func = compare_func;
return q;
}
void prioq_free(Prioq *q) {
if (!q)
return;
free(q->items);
free(q);
}
static void swap(Prioq *q, unsigned j, unsigned k) {
void *saved_data;
unsigned *saved_idx;
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);
saved_data = q->items[j].data;
saved_idx = q->items[j].idx;
q->items[j].data = q->items[k].data;
q->items[j].idx = q->items[k].idx;
q->items[k].data = saved_data;
q->items[k].idx = saved_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);
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, 16);
j = realloc(q->items, sizeof(struct prioq_item) * n);
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);
}
}
static struct prioq_item* find_item(Prioq *q, void *data, unsigned *idx) {
struct prioq_item *i;
assert(q);
if (idx) {
assert(*idx < q->n_items);
i = q->items + *idx;
assert(i->data == data);
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;
assert(q);
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(Prioq *q) {
assert(q);
if (q->n_items <= 0)
return NULL;
return q->items[0].data;
}
void *prioq_pop(Prioq *q) {
void *data;
assert(q);
if (q->n_items <= 0)
return NULL;
data = q->items[0].data;
remove_item(q, q->items);
return data;
}
unsigned prioq_size(Prioq *q) {
assert(q);
return q->n_items;
}
bool prioq_isempty(Prioq *q) {
assert(q);
return q->n_items <= 0;
}

39
src/shared/prioq.h

@ -0,0 +1,39 @@
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
#pragma once
/***
This file is part of systemd.
Copyright 2013 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include "hashmap.h"
typedef struct Prioq Prioq;
Prioq *prioq_new(compare_func_t compare);
void prioq_free(Prioq *q);
int prioq_put(Prioq *q, void *data, unsigned *idx);
int prioq_remove(Prioq *q, void *data, unsigned *idx);
int prioq_reshuffle(Prioq *q, void *data, unsigned *idx);
void *prioq_peek(Prioq *q);
void *prioq_pop(Prioq *q);
unsigned prioq_size(Prioq *q);
bool prioq_isempty(Prioq *q);

166
src/test/test-prioq.c

@ -0,0 +1,166 @@
/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
/***
This file is part of systemd.
Copyright 2013 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <stdlib.h>
#include "util.h"
#include "set.h"
#include "prioq.h"
#define SET_SIZE 1024*4
static int unsigned_compare(const void *a, const void *b) {
const unsigned *x = a, *y = b;
if (*x < *y)
return -1;
if (*x > *y)
return 1;
return 0;
}
static void test_unsigned(void) {
unsigned buffer[SET_SIZE], i;
Prioq *q;
srand(0);
q = prioq_new(trivial_compare_func);
assert_se(q);
for (i = 0; i < ELEMENTSOF(buffer); i++) {
unsigned u;
u = (unsigned) rand();
buffer[i] = u;
assert_se(prioq_put(q, UINT_TO_PTR(u), NULL) >= 0);
}
qsort(buffer, ELEMENTSOF(buffer), sizeof(buffer[0]), unsigned_compare);
for (i = 0; i < ELEMENTSOF(buffer); i++) {
unsigned u;
assert_se(prioq_size(q) == ELEMENTSOF(buffer) - i);
u = PTR_TO_UINT(prioq_pop(q));
assert_se(buffer[i] == u);
}
assert_se(prioq_isempty(q));
prioq_free(q);
}
struct test {
unsigned value;
unsigned idx;
};
static int test_compare(const void *a, const void *b) {
const struct test *x = a, *y = b;
if (x->value < y->value)
return -1;
if (x->value > y->value)
return 1;
return 0;
}
static unsigned test_hash(const void *a) {
const struct test *x = a;
return x->value;
}
static void test_struct(void) {
Prioq *q;
Set *s;
unsigned previous = 0, i;
int r;
srand(0);
q = prioq_new(test_compare);
assert_se(q);
s = set_new(test_hash, test_compare);
assert_se(s);
for (i = 0; i < SET_SIZE; i++) {
struct test *t;
t = new0(struct test, 1);
assert_se(t);
t->value = (unsigned) rand();
r = prioq_put(q, t, &t->idx);
assert_se(r >= 0);
if (i % 4 == 0) {
r = set_put(s, t);
assert_se(r >= 0);
}
}
for (;;) {
struct test *t;
t = set_steal_first(s);
if (!t)
break;
r = prioq_remove(q, t, &t->idx);
assert_se(r > 0);
free(t);
}
for (i = 0; i < SET_SIZE * 3 / 4; i++) {
struct test *t;
assert_se(prioq_size(q) == (SET_SIZE * 3 / 4) - i);
t = prioq_pop(q);
assert_se(t);
assert_se(previous <= t->value);
previous = t->value;
free(t);
}
assert_se(prioq_isempty(q));
prioq_free(q);
assert_se(set_isempty(s));
set_free(s);
}
int main(int argc, char* argv[]) {
test_unsigned();
test_struct();
return 0;
}
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