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

deps/teagba/src/gfx.cpp

@@ -0,0 +1,40 @@
+/*
+ * Copyright 2016 - 2023 Gary Talent (gary@drinkingtea.net). All rights reserved.
+ */
+
+#include <teagba/addresses.hpp>
+#include <teagba/bios.hpp>
+#include <teagba/irq.hpp>
+
+#include <teagba/gfx.hpp>
+
+namespace teagba {
+
+volatile uint16_t g_spriteUpdates = 0;
+ox::Array<GbaSpriteAttrUpdate, 128> g_spriteBuffer;
+
+void addSpriteUpdate(const GbaSpriteAttrUpdate &upd) noexcept {
+	// block until g_spriteUpdates is less than buffer len
+	if (g_spriteUpdates >= g_spriteBuffer.size()) [[unlikely]] {
+		teagba_vblankintrwait();
+	}
+	const auto ie = REG_IE; // disable vblank interrupt handler
+	REG_IE = REG_IE & static_cast<uint16_t>(~teagba::Int_vblank); // disable vblank interrupt handler
+	const auto updateCnt = g_spriteUpdates;
+	g_spriteBuffer[updateCnt] = upd;
+	g_spriteUpdates = updateCnt + 1;
+	REG_IE = ie; // enable vblank interrupt handler
+}
+
+void applySpriteUpdates() noexcept {
+	// copy g_spriteUpdates to allow it to use a register instead of reading
+	// from memory every iteration of the loop, needed because g_spriteUpdates
+	// is volatile
+	const unsigned updates = g_spriteUpdates;
+	for (unsigned i = 0; i < updates; ++i) {
+		const auto &oa = g_spriteBuffer[i];
+		MEM_OAM[oa.idx] = *reinterpret_cast<const uint64_t*>(&oa);
+	}
+}
+
+}