Update APU skeleton

src/app/emu/apu.cc

@@ -0,0 +1,66 @@
+#include "app/emu/apu.h"
+
+#include <cstdint>
+#include <iostream>
+#include <vector>
+
+#include "app/emu/mem.h"
+
+namespace yaze {
+namespace app {
+namespace emu {
+
+APU::APU(Memory& memory) : memory_(memory) {}
+
+void APU::Init() {
+  // Initialize registers
+  // ...
+}
+
+void APU::Reset() {
+  // Render background layers
+  // ...
+
+  // Render sprites
+  // ...
+}
+
+void APU::Run(int cycles) {
+  // ...
+}
+
+uint8_t APU::ReadRegister(uint16_t address) {
+  // ...
+}
+
+void APU::WriteRegister(uint16_t address, uint8_t value) {
+  // ...
+}
+
+const std::vector<int16_t>& APU::GetAudioSamples() const {
+  // ...
+}
+
+void APU::UpdateChannelSettings() {
+  // ...
+}
+
+int16_t APU::GenerateSample(int channel) {
+  // ...
+}
+
+void APU::ApplyEnvelope(int channel) {
+  // ...
+}
+
+uint8_t APU::ReadDSPMemory(uint16_t address) {
+  // ...
+}
+
+void APU::WriteDSPMemory(uint16_t address, uint8_t value) {
+  // ...
+}
+
+}  // namespace emu
+}  // namespace app
+}  // namespace yaze