1 files changed, 149 insertions, 0 deletions
diff --git a/timer.c b/timer.c
new file mode 100644
index 0000000..96eb453
--- /dev/null
+++ b/timer.c
@@ -0,0 +1,149 @@
+
+
+#ifdef _WIN32
+#define WIN32_LEAN_AND_MEAN
+#include <windows.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+struct timer_handle {
+	HANDLE htimer;
+	uint64_t interval_ns;
+	uint64_t qpc_frequency;
+	uint64_t next_deadline;
+	bool started;
+};
+
+static inline uint64_t qpc_now_ns(uint64_t freq) {
+	LARGE_INTEGER qpc;
+	QueryPerformanceCounter(&qpc);
+	return (uint64_t)((qpc.QuadPart * 1000000000ULL) / freq);
+}
+
+struct timer_handle *timer_new(uint64_t interval_ns) {
+	struct timer_handle *t = (struct timer_handle *)HeapAlloc(GetProcessHeap(), HEAP_ZERO_MEMORY, sizeof(struct timer_handle));
+	if(!t) return 0;
+
+	t->htimer = CreateWaitableTimerW(0, TRUE, 0);
+	if(!t->htimer) {
+		HeapFree(GetProcessHeap(), 0, t);
+		return 0;
+	}
+
+	LARGE_INTEGER freq;
+	QueryPerformanceFrequency(&freq);
+	t->qpc_frequency = freq.QuadPart;
+	t->interval_ns = interval_ns;
+	t->started = false;
+
+	return t;
+}
+
+bool timer_start(struct timer_handle *t) {
+	t->next_deadline = qpc_now_ns(t->qpc_frequency) + t->interval_ns;
+	t->started = true;
+	return true;
+}
+
+bool timer_wait(struct timer_handle *t) {
+	if(!t->started) return false;
+
+	uint64_t now = qpc_now_ns(t->qpc_frequency);
+	if(t->next_deadline <= now) {
+		t->next_deadline += t->interval_ns;
+		return true;
+	}
+
+	uint64_t sleep_ns = t->next_deadline - now;
+	if(sleep_ns > 500000) { // > 0.5ms
+		LARGE_INTEGER due;
+		due.QuadPart = -(int64_t)((sleep_ns - 500000) / 100); // 100ns units, negative = relative
+		SetWaitableTimer(t->htimer, &due, 0, 0, 0, 0);
+		WaitForSingleObject(t->htimer, INFINITE);
+	}
+
+	while(qpc_now_ns(t->qpc_frequency) < t->next_deadline) {
+		YieldProcessor(); // pause instruction
+	}
+
+	t->next_deadline += t->interval_ns;
+	return true;
+}
+
+void timer_destroy(struct timer_handle *t) {
+	if(t) {
+		if(t->htimer) CloseHandle(t->htimer);
+		HeapFree(GetProcessHeap(), 0, t);
+	}
+}
+
+
+#else // Linux
+#include <sys/timerfd.h>
+#include <sys/epoll.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+struct timer_handle {
+	int tfd;
+	int epfd;
+	struct itimerspec spec;
+	int started;
+};
+
+static struct timer_handle *timer_new(uint64_t interval_ns) {
+	struct timer_handle *t = (struct timer_handle *)malloc(sizeof(struct timer_handle));
+	if(!t) return 0;
+
+	t->tfd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC);
+	if(t->tfd < 0) { free(t); return 0; }
+
+	t->epfd = epoll_create1(EPOLL_CLOEXEC);
+	if(t->epfd < 0) {
+		close(t->tfd); free(t); return 0;
+	}
+
+	struct epoll_event ev = { .events = EPOLLIN, .data = { .fd = t->tfd } };
+	epoll_ctl(t->epfd, EPOLL_CTL_ADD, t->tfd, &ev);
+
+	t->spec.it_interval.tv_sec = interval_ns / 1000000000ULL;
+	t->spec.it_interval.tv_nsec = interval_ns % 1000000000ULL;
+	t->spec.it_value.tv_sec = 0;
+	t->spec.it_value.tv_nsec = 0;
+	t->started = 0;
+
+	return t;
+}
+
+static bool timer_start(struct timer_handle *t) {
+	if(t->started) return true;
+
+	t->spec.it_value = t->spec.it_interval;
+	if(timerfd_settime(t->tfd, 0, &t->spec, 0)) return false;
+
+	t->started = 1;
+	return true;
+}
+
+static bool timer_wait(struct timer_handle *t) {
+	if(!t->started) return false;
+
+	struct epoll_event ev;
+	int r = epoll_wait(t->epfd, &ev, 1, -1);
+	if(r < 0) return false;
+	uint64_t expirations;
+	read(t->tfd, &expirations, sizeof(expirations));
+	return true;
+}
+
+static void timer_destroy(struct timer_handle *t) {
+	if(t) {
+		if(t->tfd >= 0) close(t->tfd);
+		if(t->epfd >= 0) close(t->epfd);
+		free(t);
+	}
+}
+
+#endif