Singleflight Pattern: C'de Tekrarlanan İşleri Engelleme

1#include <stdio.h>
2#include <stdlib.h>
3#include <string.h>
4#include <pthread.h>
5#include <unistd.h>
6
7typedef struct {
8char *result;
9int done;
10pthread_mutex_t mu;
11pthread_cond_t cond;
12} Flight;
13
14Flight *flight_new() {
15Flight *f = malloc(sizeof(Flight));
16f->result = NULL;
17f->done = 0;
18pthread_mutex_init(&f->mu, NULL);
19pthread_cond_init(&f->cond, NULL);
20return f;
21}
22
23void flight_set_result(Flight *f, const char *result) {
24pthread_mutex_lock(&f->mu);
25f->result = malloc(strlen(result) + 1);
26strcpy(f->result, result);
27f->done = 1;
28pthread_cond_broadcast(&f->cond);
29pthread_mutex_unlock(&f->mu);
30}
31
32const char *flight_wait(Flight *f) {
33pthread_mutex_lock(&f->mu);
34while (!f->done) {
35pthread_cond_wait(&f->cond, &f->mu);
36}
37const char *res = f->result;
38pthread_mutex_unlock(&f->mu);
39return res;
40}
41
42void flight_free(Flight *f) {
43if (f->result) free(f->result);
44pthread_mutex_destroy(&f->mu);
45pthread_cond_destroy(&f->cond);
46free(f);
47}
48
49Flight *cache = NULL;
50
51void *expensive_work(void *arg) {
52printf("[Thread %ld] İş başladı\n", (long)pthread_self());
53sleep(2);
54printf("[Thread %ld] İş bitti\n", (long)pthread_self());
55return NULL;
56}
57
58const char *get_data() {
59if (!cache) {
60cache = flight_new();
61pthread_t tid;
62pthread_create(&tid, NULL, expensive_work, NULL);
63pthread_detach(tid);
64sleep(2);
65flight_set_result(cache, "Veri: 42");
66}
67return flight_wait(cache);
68}
69
70int main() {
71printf("İstek 1: %s\n", get_data());
72printf("İstek 2: %s\n", get_data());
73printf("İstek 3: %s\n", get_data());
74
75if (cache) flight_free(cache);
76return 0;
77}

1[Thread...] İş başladı
2[Thread...] İş bitti
3İstek 1: Veri: 42
4İstek 2: Veri: 42
5İstek 3: Veri: 42