Move kissfft to engine/third_party and add AudioMixer class

engine/include/XCEngine/Audio/AudioMixer.h

@@ -0,0 +1,56 @@
+#pragma once
+
+#include <XCEngine/Audio/AudioTypes.h>
+#include <XCEngine/Math/Vector3.h>
+#include <vector>
+#include <map>
+#include <string>
+
+namespace XCEngine {
+namespace Audio {
+
+class IAudioEffect;
+
+class AudioMixer {
+public:
+    AudioMixer();
+    ~AudioMixer();
+
+    void SetVolume(float volume);
+    float GetVolume() const { return m_volume; }
+
+    void SetMute(bool mute);
+    bool IsMute() const { return m_mute; }
+
+    void AddEffect(IAudioEffect* effect);
+    void RemoveEffect(IAudioEffect* effect);
+    void ClearEffects();
+
+    void ProcessAudio(float* buffer, uint32 sampleCount, uint32 channels);
+
+    void SetOutputMixer(AudioMixer* mixer);
+    AudioMixer* GetOutputMixer() const { return m_outputMixer; }
+
+    void Set3DParams(const Audio3DParams& params);
+    const Audio3DParams& Get3DParams() const { return m_3DParams; }
+
+    struct ChannelVolume {
+        float volume = 1.0f;
+        bool mute = false;
+    };
+    void SetChannelVolume(AudioChannel channel, float volume);
+    float GetChannelVolume(AudioChannel channel) const;
+
+private:
+    float m_volume = 1.0f;
+    bool m_mute = false;
+
+    Audio3DParams m_3DParams;
+    AudioMixer* m_outputMixer = nullptr;
+
+    std::vector<IAudioEffect*> m_effects;
+    std::map<AudioChannel, ChannelVolume> m_channelVolumes;
+};
+
+} // namespace Audio
+} // namespace XCEngine