Common: Add a NullAudioStream implementation

src/common/CMakeLists.txt

@@ -20,6 +20,8 @@ add_library(common
   iso_reader.h
   jit_code_buffer.cpp
   jit_code_buffer.h
+  null_audio_stream.cpp
+  null_audio_stream.h
   rectangle.h
   state_wrapper.cpp
   state_wrapper.h

src/common/audio_stream.cpp

@@ -97,6 +97,7 @@ void AudioStream::WriteSamples(const SampleType* samples, u32 num_samples)
       m_num_free_buffers--;
       m_first_free_buffer = (m_first_free_buffer + 1) % m_buffers.size();
       m_num_available_buffers++;
+      BufferAvailable();
     }
   }
 }
@@ -116,6 +117,7 @@ void AudioStream::EndWrite(u32 num_samples)
     m_num_free_buffers--;
     m_first_free_buffer = (m_first_free_buffer + 1) % m_buffers.size();
     m_num_available_buffers++;
+    BufferAvailable();
   }
 
   m_buffer_mutex.unlock();

src/common/audio_stream.h

@@ -45,11 +45,14 @@ protected:
   virtual bool OpenDevice() = 0;
   virtual void PauseDevice(bool paused) = 0;
   virtual void CloseDevice() = 0;
+  virtual void BufferAvailable() = 0;
 
   bool IsDeviceOpen() const { return (m_output_sample_rate > 0); }
 
   u32 ReadSamples(SampleType* samples, u32 num_samples);
 
+  void DropBuffer();
+
   u32 m_output_sample_rate = 0;
   u32 m_channels = 0;
   u32 m_buffer_size = 0;
@@ -64,7 +67,6 @@ private:
 
   void AllocateBuffers(u32 buffer_count);
   void EnsureBuffer();
-  void DropBuffer();
 
   std::vector<Buffer> m_buffers;
   std::mutex m_buffer_mutex;

src/common/common.vcxproj

@@ -49,6 +49,7 @@
     <ClInclude Include="heap_array.h" />
     <ClInclude Include="iso_reader.h" />
     <ClInclude Include="jit_code_buffer.h" />
+    <ClInclude Include="null_audio_stream.h" />
     <ClInclude Include="rectangle.h" />
     <ClInclude Include="cd_subchannel_replacement.h" />
     <ClInclude Include="state_wrapper.h" />
@@ -70,6 +71,7 @@
     <ClCompile Include="iso_reader.cpp" />
     <ClCompile Include="jit_code_buffer.cpp" />
     <ClCompile Include="cd_subchannel_replacement.cpp" />
+    <ClCompile Include="null_audio_stream.cpp" />
     <ClCompile Include="state_wrapper.cpp" />
     <ClCompile Include="cd_xa.cpp" />
   </ItemGroup>

src/common/common.vcxproj.filters

@@ -34,6 +34,7 @@
     <ClInclude Include="iso_reader.h" />
     <ClInclude Include="cd_image.h" />
     <ClInclude Include="cd_subchannel_replacement.h" />
+    <ClInclude Include="null_audio_stream.h" />
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="jit_code_buffer.cpp" />
@@ -66,6 +67,7 @@
     </ClCompile>
     <ClCompile Include="iso_reader.cpp" />
     <ClCompile Include="cd_subchannel_replacement.cpp" />
+    <ClCompile Include="null_audio_stream.cpp" />
   </ItemGroup>
   <ItemGroup>
     <Natvis Include="bitfield.natvis" />

src/common/null_audio_stream.cpp

@@ -0,0 +1,20 @@
+#include "null_audio_stream.h"
+
+NullAudioStream::NullAudioStream() = default;
+
+NullAudioStream::~NullAudioStream() = default;
+
+bool NullAudioStream::OpenDevice()
+{
+  return true;
+}
+
+void NullAudioStream::PauseDevice(bool paused) {}
+
+void NullAudioStream::CloseDevice() {}
+
+void NullAudioStream::BufferAvailable()
+{
+  // drop any buffer as soon as they're available
+  DropBuffer();
+}

src/common/null_audio_stream.h

@@ -0,0 +1,17 @@
+#pragma once
+#include "audio_stream.h"
+
+class NullAudioStream final : public AudioStream
+{
+public:
+  NullAudioStream();
+  ~NullAudioStream();
+
+  static std::unique_ptr<AudioStream> Create();
+
+protected:
+  bool OpenDevice() override;
+  void PauseDevice(bool paused) override;
+  void CloseDevice() override;
+  void BufferAvailable() override;
+};

src/duckstation/sdl_audio_stream.cpp

@@ -59,3 +59,5 @@ void SDLAudioStream::AudioCallback(void* userdata, uint8_t* stream, int len)
                 silence_samples * this_ptr->m_channels * sizeof(SampleType));
   }
 }
+
+void SDLAudioStream::BufferAvailable() {}

src/duckstation/sdl_audio_stream.h

@@ -12,6 +12,7 @@ protected:
   bool OpenDevice() override;
   void PauseDevice(bool paused) override;
   void CloseDevice() override;
+  void BufferAvailable() override;
 
   static void AudioCallback(void* userdata, uint8_t* stream, int len);