[nostalgia] Integrate Ox Preloader

src/nostalgia/core/gba/core.cpp

@@ -37,13 +37,31 @@ static void initTimer() noexcept {
 	REG_IE = REG_IE | Int_timer0;
 }
 
+static ox::Result<std::size_t> findPreloadSection() noexcept {
+	// put the header in the wrong order to prevent mistaking this code for the
+	// media section
+	constexpr auto headerP2 = "D_HEADER________";
+	constexpr auto headerP1 = "NOSTALGIA_PRELOA";
+	constexpr auto headerP1Len = ox_strlen(headerP2);
+	constexpr auto headerP2Len = ox_strlen(headerP1);
+	constexpr auto headerLen = headerP1Len + headerP2Len;
+	for (auto current = MEM_ROM; current < reinterpret_cast<char*>(0x0a000000); current += headerLen) {
+		if (ox_memcmp(current, headerP1, headerP1Len) == 0 &&
+		    ox_memcmp(current + headerP1Len, headerP2, headerP2Len) == 0) {
+			return reinterpret_cast<std::size_t>(current + headerLen);
+		}
+	}
+	return OxError(1);
+}
+
 ox::Result<ox::UniquePtr<Context>> init(ox::UniquePtr<ox::FileSystem> fs, const char *appName) noexcept {
 	auto ctx = ox::make_unique<Context>();
 	ctx->rom = std::move(fs);
-	ctx->appName = std::move(appName);
+	ctx->appName = appName;
 	oxReturnError(initGfx(ctx.get()));
 	initTimer();
 	initIrq();
+	oxReturnError(findPreloadSection().moveTo(&ctx->preloadSectionOffset));
 	return ctx;
 }