[nostalgia] Break part of core out into Turbine and TeaGBA libraries

src/turbine/gba/turbine.arm.cpp

@@ -0,0 +1,41 @@
+/*
+ * Copyright 2016 - 2023 Gary Talent (gary@drinkingtea.net). All rights reserved.
+ */
+
+#include <teagba/addresses.hpp>
+#include <teagba/bios.hpp>
+#include <teagba/irq.hpp>
+
+#include "context.hpp"
+#include "turbine.hpp"
+
+namespace turbine {
+
+extern volatile gba_timer_t g_timerMs;
+gba_timer_t g_wakeupTime;
+
+ox::Error run(Context &ctx) noexcept {
+	g_wakeupTime = 0;
+	const auto gbaCtx = static_cast<gba::Context*>(&ctx);
+	while (gbaCtx->running) {
+		if (g_wakeupTime <= g_timerMs && ctx.updateHandler) {
+			auto sleepTime = ctx.updateHandler(ctx);
+			if (sleepTime >= 0) {
+				g_wakeupTime = g_timerMs + static_cast<unsigned>(sleepTime);
+			} else {
+				g_wakeupTime = ~gba_timer_t(0);
+			}
+		}
+		if constexpr(config::GbaEventLoopTimerBased) {
+			// wait for timer interrupt
+			teagba_intrwait(
+					0,
+					teagba::Int_timer0 | teagba::Int_timer1 | teagba::Int_timer2 | teagba::Int_timer3);
+		} else {
+			teagba_vblankintrwait();
+		}
+	}
+	return {};
+}
+
+}