common: Add AudioStream class

src/common/audio_stream.h

@@ -0,0 +1,77 @@
+#pragma once
+#include "types.h"
+#include <memory>
+#include <mutex>
+#include <vector>
+
+// Uses signed 16-bits samples.
+
+class AudioStream
+{
+public:
+  using SampleType = s16;
+
+  enum
+  {
+    DefaultOutputSampleRate = 44100,
+    DefaultBufferSize = 2048,
+    DefaultBufferCount = 3,
+  };
+
+  AudioStream();
+  virtual ~AudioStream();
+
+  u32 GetOutputSampleRate() const { return m_output_sample_rate; }
+  u32 GetChannels() const { return m_channels; }
+  u32 GetBufferSize() const { return m_buffer_size; }
+  u32 GetBufferCount() const { return static_cast<u32>(m_buffers.size()); }
+
+  bool Reconfigure(u32 output_sample_rate = DefaultOutputSampleRate, u32 channels = 1,
+                   u32 buffer_size = DefaultBufferSize, u32 buffer_count = DefaultBufferCount);
+
+  void PauseOutput(bool paused);
+  void EmptyBuffers();
+
+  void Shutdown();
+
+  void BeginWrite(SampleType** buffer_ptr, u32* num_samples);
+  void WriteSamples(const SampleType* samples, u32 num_samples);
+  void EndWrite(u32 num_samples);
+
+protected:
+  virtual bool OpenDevice() = 0;
+  virtual void PauseDevice(bool paused) = 0;
+  virtual void CloseDevice() = 0;
+
+  bool IsDeviceOpen() const { return (m_output_sample_rate > 0); }
+
+  u32 ReadSamples(SampleType* samples, u32 num_samples);
+
+  u32 m_output_sample_rate = 0;
+  u32 m_channels = 0;
+  u32 m_buffer_size = 0;
+
+private:
+  struct Buffer
+  {
+    std::vector<SampleType> data;
+    u32 write_position;
+    u32 read_position;
+  };
+
+  void AllocateBuffers(u32 buffer_count);
+  void DropBuffer();
+
+  std::vector<Buffer> m_buffers;
+  std::mutex m_buffer_lock;
+
+  // For input.
+  u32 m_first_free_buffer = 0;
+  u32 m_num_free_buffers = 0;
+
+  // For output.
+  u32 m_num_available_buffers = 0;
+  u32 m_first_available_buffer = 0;
+
+  bool m_output_paused = true;
+};