Android: Add OpenSL ES audio backend

android/app/src/cpp/opensles_audio_stream.h

@@ -0,0 +1,48 @@
+#pragma once
+#include "common/audio_stream.h"
+#include <SLES/OpenSLES.h>
+#include <SLES/OpenSLES_Android.h>
+#include <array>
+#include <memory>
+
+class OpenSLESAudioStream final : public AudioStream
+{
+public:
+  OpenSLESAudioStream();
+  ~OpenSLESAudioStream();
+
+  static std::unique_ptr<AudioStream> Create();
+
+  void SetOutputVolume(u32 volume) override;
+
+protected:
+  enum : u32
+  {
+    NUM_BUFFERS = 2
+  };
+
+  ALWAYS_INLINE bool IsOpen() const { return (m_engine != nullptr); }
+
+  bool OpenDevice() override;
+  void PauseDevice(bool paused) override;
+  void CloseDevice() override;
+  void FramesAvailable() override;
+
+  void EnqueueBuffer();
+
+  static void BufferCallback(SLAndroidSimpleBufferQueueItf buffer_queue, void* context);
+
+  SLObjectItf m_engine{};
+  SLEngineItf m_engine_engine{};
+  SLObjectItf m_output_mix{};
+
+  SLObjectItf m_player{};
+  SLPlayItf m_play_interface{};
+  SLAndroidSimpleBufferQueueItf m_buffer_queue_interface{};
+  SLVolumeItf m_volume_interface{};
+
+  std::array<std::unique_ptr<SampleType[]>, NUM_BUFFERS> m_buffers;
+  u32 m_current_buffer = 0;
+  bool m_paused = true;
+  bool m_buffer_enqueued = false;
+};