eh

ratelimit.h

@@ -0,0 +1,65 @@
+#pragma once
+#include <stddef.h>
+#include <time.h>
+#include <string.h>
+
+#ifdef RATELIMIT_THREADSAFE
+#include <pthread.h>
+#endif
+
+typedef struct {
+    ratelimit_table_type value;
+    int count;
+    double window_start;
+} ratelimit_t;
+
+static struct {
+    ratelimit_t data[256];
+    size_t next;
+#ifdef RATELIMIT_THREADSAFE
+    pthread_mutex_t lock;
+#endif
+} ratelimit_table = { {0}, 0
+#ifdef RATELIMIT_THREADSAFE
+, PTHREAD_MUTEX_INITIALIZER
+#endif
+};
+
+static int rate_limited(ratelimit_table_type value, float window, int rate_limit) {
+    struct timespec ts;
+    clock_gettime(CLOCK_MONOTONIC, &ts);
+    double now = ts.tv_sec + ts.tv_nsec * 1e-9;
+
+#ifdef RATELIMIT_THREADSAFE
+    pthread_mutex_lock(&ratelimit_table.lock);
+#endif
+
+    ratelimit_t* e = (void*)0;
+    for (size_t i = 0; i < 256; i++) {
+        if (memcmp(ratelimit_table.data[i].value, value, sizeof(ratelimit_table_type)) == 0) {
+            e = &ratelimit_table.data[i];
+            break;
+        }
+    }
+
+    if (!e) {
+        e = &ratelimit_table.data[ratelimit_table.next++];
+        memcpy(e->value, value, sizeof(ratelimit_table_type));
+        e->window_start = now;
+        e->count = 0;
+    }
+
+    if (now - e->window_start >= window) {
+        e->window_start = now;
+        e->count = 0;
+    }
+
+    const int allowed = e->count < rate_limit;
+    if (allowed) e->count++;
+
+#ifdef RATELIMIT_THREADSAFE
+    pthread_mutex_unlock(&ratelimit_table.lock);
+#endif
+
+    return allowed ? 0 : 1;
+}