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/* Copyright 2016 Google Inc.
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License. */
#include "platform.h"
#include "compiler.h"
#include "nsync.h"
#include "time_extra.h"
#include "smprintf.h"
#include "testing.h"
#include "closure.h"
#include "array.h"
#include "heap.h"
NSYNC_CPP_USING_
/* Example use of nsync_mu_wait(): A priority queue of strings whose
"remove_with_deadline" operation has a deadline. */
/* --------------------------------------- */
/* An array used as a heap of strings. */
typedef A_TYPE (const char *) a_string;
static int str_lt (const char *e0, const char *e1) {
return (strcmp (e0, e1) < 0);
}
static void no_set (const char *a UNUSED, int b UNUSED) {
}
/* --------------------------------------- */
/* A priority queue of strings, which emits the lexicographically least string
available. */
typedef struct string_priority_queue_mu_s {
nsync_mu mu; /* protects heap */
a_string heap;
} string_priority_queue_mu;
/* A wait condition for non-empty. */
static int spq_is_non_empty (const void *v) {
const string_priority_queue_mu *q = (const string_priority_queue_mu *) v;
return (A_LEN (&q->heap) != 0);
}
/* Adds "s" to the queue *q. */
static void string_priority_queue_mu_add (string_priority_queue_mu *q, const char *s) {
int alen;
nsync_mu_lock (&q->mu);
alen = A_LEN (&q->heap);
A_PUSH (&q->heap) = s;
heap_add (&A (&q->heap, 0), alen, str_lt, no_set, s);
nsync_mu_unlock (&q->mu);
}
/* Wait until queue *q is non-empty, then remove a string from its
beginning, and return it; or if abs_deadline is reached before the
queue becomes non-empty, return NULL. */
static const char *string_priority_queue_mu_remove_with_deadline (
string_priority_queue_mu *q, nsync_time abs_deadline) {
const char *s = NULL;
nsync_mu_lock (&q->mu);
if (nsync_mu_wait_with_deadline (&q->mu, &spq_is_non_empty, q, NULL,
abs_deadline, NULL) == 0) {
int alen = A_LEN (&q->heap);
if (alen != 0) {
s = A (&q->heap, 0);
heap_remove (&A (&q->heap, 0), alen, str_lt, no_set, 0);
A_DISCARD (&q->heap, 1);
}
}
nsync_mu_unlock (&q->mu);
return (s);
}
/* Free resources associates with *q */
static void string_priority_queue_mu_destroy (string_priority_queue_mu *q) {
A_FREE (&q->heap);
}
/* --------------------------------------- */
/* Add strings s[0, ..., n-1] to *q, with the specified delay between additions. */
static void add_and_wait_mu (string_priority_queue_mu *q,
nsync_time delay, int n, const char *s[]) {
int i;
for (i = 0; i != n; i++) {
string_priority_queue_mu_add (q, s[i]);
nsync_time_sleep (delay);
}
}
CLOSURE_DECL_BODY4 (add_and_wait_mu, string_priority_queue_mu *,
nsync_time, int, const char **)
typedef A_TYPE (char) a_char;
static void a_char_append (a_char *a, const char *str) {
while (*str != 0) {
A_PUSH (a) = *str;
str++;
}
}
/* Remove the first item from *q and output it on stdout,
or output "timeout: <delay>" if no value can be found before "delay" elapses. */
static void remove_and_print_mu (string_priority_queue_mu *q, nsync_time delay, a_char *output) {
const char *s;
if ((s = string_priority_queue_mu_remove_with_deadline (q,
nsync_time_add (nsync_time_now (), delay))) != NULL) {
a_char_append (output, s);
a_char_append (output, "\n");
} else {
char buf[64];
snprintf (buf, sizeof (buf), "timeout %gs\n",
nsync_time_to_dbl (delay));
a_char_append (output, buf);
}
}
/* Demonstrate the use of nsync_mu_wait() via a priority queue of strings.
See the routine string_priority_queue_mu_remove_with_deadline(), above. */
static void example_mu_wait (testing t) {
static const char *input[] = { "one", "two", "three", "four", "five" };
string_priority_queue_mu q;
a_char output;
static const char *expected =
"one\n"
"three\n"
"two\n"
"timeout 0.1s\n"
"four\n"
"timeout 0.1s\n"
"five\n"
"timeout 1s\n";
memset ((void *) &q, 0, sizeof (q));
memset (&output, 0, sizeof (output));
closure_fork (closure_add_and_wait_mu (&add_and_wait_mu, &q, nsync_time_ms (500),
NELEM (input), input));
/* delay: "one", "two", "three"; not yet "four" */
nsync_time_sleep (nsync_time_ms (1200));
remove_and_print_mu (&q, nsync_time_ms (1000), &output); /* "one" */
remove_and_print_mu (&q, nsync_time_ms (1000), &output); /* "three" (less than "two") */
remove_and_print_mu (&q, nsync_time_ms (1000), &output); /* "two" */
remove_and_print_mu (&q, nsync_time_ms (100), &output); /* time out because 1.3 < 0.5*3 */
remove_and_print_mu (&q, nsync_time_ms (1000), &output); /* "four" */
remove_and_print_mu (&q, nsync_time_ms (100), &output); /* time out because 0.1 < 0.5 */
remove_and_print_mu (&q, nsync_time_ms (1000), &output); /* "five" */
remove_and_print_mu (&q, nsync_time_ms (1000), &output); /* time out: no more to fetch */
A_PUSH (&output) = 0;
if (strcmp (&A (&output, 0), expected) != 0) {
TEST_ERROR (t, ("expected = %s\ngot = %s\n", expected, &A (&output, 0)));
}
A_FREE (&output);
string_priority_queue_mu_destroy (&q);
}
int main (int argc, char *argv[]) {
testing_base tb = testing_new (argc, argv, 0);
TEST_RUN (tb, example_mu_wait);
return (testing_base_exit (tb));
}
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