write code for a timing

src/game/time.c

@@ -0,0 +1,39 @@
+#include "time.h"
+
+#include <stdbool.h>
+#include <time.h>
+
+#if __has_include(<features.h>)
+#include <features.h>
+#endif
+#if __has_include(<features.h>) && _POSIX_C_SOURCE >= 199309L
+#include <bits/time.h>
+static void gettime(struct timespec* ts) {
+	clock_gettime(CLOCK_MONOTONIC, ts);
+}
+#elif defined(_WIN32)
+#include <profileapi.h>
+#include <windows.h>
+#include <winnt.h>
+static void gettime(struct timespec* ts) {
+	LARGE_INTEGER cnt, frq;
+	QueryPerformanceCounter(&cnt);
+	QueryPerformanceFrequency(&frq);
+	ts->tv_sec = (time_t)(cnt.QuadPart / frq.QuadPart);
+	ts->tv_nsec = (time_t)((cnt.QuadPart % frq.QuadPart) * 1000000000 / frq.QuadPart);
+}
+#else
+#error no implementation of a monotonic clock was available
+#endif
+
+time_t time_pull(void) {
+	struct timespec ts;
+	gettime(&ts);
+	return ts.tv_sec * 1000 + ts.tv_nsec / 1000000;
+}
+
+int time_poll(time_t curr, time_t delta, time_t* restrict proj) {
+	bool tpass = curr >= *proj;
+	*proj += tpass * ((curr + delta) - *proj); // adds 0, or the difference to proj
+	return tpass;
+}

src/game/time.h

@@ -0,0 +1,12 @@
+#pragma once
+
+#include <sys/cdefs.h>
+#include <time.h>
+
+/* gets the current time in milliseconds */
+time_t time_pull(void);
+
+/* Polls the time whether a given timeout has passed, comparing against `curr` as the current time.
+ * if `curr` ≥ `*proj`, `curr` + `delta` is written to `*proj`. `1` is returned.
+ * otherwise, we just return `0`. */
+__nonnull((3)) int time_poll(time_t curr, time_t delta, time_t* restrict proj);