Added PIT support, sleep() exists!

src/kernel/timer.c

@@ -0,0 +1,31 @@
+#include "timer.h"
+#include "stdint.h"
+#include "idt.h"
+#include "irq.h"
+#include "system.h"
+
+uint32_t timerTicks = 0;
+
+void timerHandler() {
+    timerTicks++;
+}
+
+void setupTimer() {
+    installIrqHandler(0, timerHandler);
+}
+
+// Source: https://en.wikibooks.org/wiki/X86_Assembly/Programmable_Interval_Timer
+void timerPhase(uint32_t hz) {
+    uint16_t div = INPUT_CLK / hz;
+
+    outb(0x43, 0x36); // Tell PIT that we're setting channel 0
+    outb(0x40, div & 0xff); // Low byte
+    outb(0X40, div >> 8); // High byte
+}
+
+void sleep(uint32_t ticks) {
+    uint32_t eticks = ticks + timerTicks;
+    
+    while (timerTicks != eticks); // Should avoid overflows unlike '<'
+}
+