From 14c3d4716fa4abfa7cc70f056676f935ba302c8a Mon Sep 17 00:00:00 2001
From: Michael Maltese <michaeljosephmaltese@gmail.com>
Date: Sun, 23 Apr 2017 19:11:43 -0700
Subject: [PATCH] AudioStretcher: split StretchAudio into ProcessSamples /
 GetStretchedSamples

---
 Source/Core/AudioCommon/AudioStretcher.cpp |  8 ++++++--
 Source/Core/AudioCommon/AudioStretcher.h   |  5 +++--
 Source/Core/AudioCommon/Mixer.cpp          | 17 ++++++++++-------
 Source/Core/AudioCommon/Mixer.h            |  2 +-
 4 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/Source/Core/AudioCommon/AudioStretcher.cpp b/Source/Core/AudioCommon/AudioStretcher.cpp
index 3414934a81..88721b0e35 100644
--- a/Source/Core/AudioCommon/AudioStretcher.cpp
+++ b/Source/Core/AudioCommon/AudioStretcher.cpp
@@ -2,7 +2,9 @@
 // Licensed under GPLv2+
 // Refer to the license.txt file included.
 
+#include <algorithm>
 #include <cmath>
+#include <cstddef>
 
 #include "AudioCommon/AudioStretcher.h"
 #include "Common/Logging/Log.h"
@@ -27,8 +29,7 @@ void AudioStretcher::Clear()
   m_sound_touch.clear();
 }
 
-void AudioStretcher::StretchAudio(const short* in, unsigned int num_in, short* out,
-                                  unsigned int num_out)
+void AudioStretcher::ProcessSamples(const short* in, unsigned int num_in, unsigned int num_out)
 {
   const double time_delta = static_cast<double>(num_out) / m_sample_rate;  // seconds
 
@@ -65,7 +66,10 @@ void AudioStretcher::StretchAudio(const short* in, unsigned int num_in, short* o
             m_stretch_ratio, backlog_fullness, lpf_gain);
 
   m_sound_touch.putSamples(in, num_in);
+}
 
+void AudioStretcher::GetStretchedSamples(short* out, unsigned int num_out)
+{
   const size_t samples_received = m_sound_touch.receiveSamples(out, num_out);
 
   if (samples_received != 0)
diff --git a/Source/Core/AudioCommon/AudioStretcher.h b/Source/Core/AudioCommon/AudioStretcher.h
index 0fdc2f09f5..b914fb924b 100644
--- a/Source/Core/AudioCommon/AudioStretcher.h
+++ b/Source/Core/AudioCommon/AudioStretcher.h
@@ -13,8 +13,9 @@ namespace AudioCommon
 class AudioStretcher
 {
 public:
-  AudioStretcher(unsigned int sample_rate);
-  void StretchAudio(const short* in, unsigned int num_in, short* out, unsigned int num_out);
+  explicit AudioStretcher(unsigned int sample_rate);
+  void ProcessSamples(const short* in, unsigned int num_in, unsigned int num_out);
+  void GetStretchedSamples(short* out, unsigned int num_out);
   void Clear();
 
 private:
diff --git a/Source/Core/AudioCommon/Mixer.cpp b/Source/Core/AudioCommon/Mixer.cpp
index 8d4ef3bc81..659deb819f 100644
--- a/Source/Core/AudioCommon/Mixer.cpp
+++ b/Source/Core/AudioCommon/Mixer.cpp
@@ -129,18 +129,19 @@ unsigned int CMixer::Mix(short* samples, unsigned int num_samples)
     unsigned int available_samples =
         std::min(m_dma_mixer.AvailableSamples(), m_streaming_mixer.AvailableSamples());
 
-    m_stretch_buffer.fill(0);
+    m_scratch_buffer.fill(0);
 
-    m_dma_mixer.Mix(m_stretch_buffer.data(), available_samples, false);
-    m_streaming_mixer.Mix(m_stretch_buffer.data(), available_samples, false);
-    m_wiimote_speaker_mixer.Mix(m_stretch_buffer.data(), available_samples, false);
+    m_dma_mixer.Mix(m_scratch_buffer.data(), available_samples, false);
+    m_streaming_mixer.Mix(m_scratch_buffer.data(), available_samples, false);
+    m_wiimote_speaker_mixer.Mix(m_scratch_buffer.data(), available_samples, false);
 
     if (!m_is_stretching)
     {
       m_stretcher.Clear();
       m_is_stretching = true;
     }
-    m_stretcher.StretchAudio(m_stretch_buffer.data(), available_samples, samples, num_samples);
+    m_stretcher.ProcessSamples(m_scratch_buffer.data(), available_samples, num_samples);
+    m_stretcher.GetStretchedSamples(samples, num_samples);
   }
   else
   {
@@ -160,11 +161,13 @@ unsigned int CMixer::MixSurround(float* samples, unsigned int num_samples)
 
   memset(samples, 0, num_samples * 6 * sizeof(float));
 
-  unsigned int available_samples = Mix(m_stretch_buffer.data(), num_samples);
+  // Mix() may also use m_scratch_buffer internally, but is safe because it alternates reads and
+  // writes.
+  unsigned int available_samples = Mix(m_scratch_buffer.data(), num_samples);
   for (size_t i = 0; i < static_cast<size_t>(available_samples) * 2; ++i)
   {
     m_float_conversion_buffer[i] =
-        m_stretch_buffer[i] / static_cast<float>(std::numeric_limits<short>::max());
+        m_scratch_buffer[i] / static_cast<float>(std::numeric_limits<short>::max());
   }
 
   DPL2Decode(m_float_conversion_buffer.data(), available_samples, samples);
diff --git a/Source/Core/AudioCommon/Mixer.h b/Source/Core/AudioCommon/Mixer.h
index 813268c903..2707df3383 100644
--- a/Source/Core/AudioCommon/Mixer.h
+++ b/Source/Core/AudioCommon/Mixer.h
@@ -81,7 +81,7 @@ private:
 
   bool m_is_stretching = false;
   AudioCommon::AudioStretcher m_stretcher;
-  std::array<short, MAX_SAMPLES * 2> m_stretch_buffer;
+  std::array<short, MAX_SAMPLES * 2> m_scratch_buffer;
   std::array<float, MAX_SAMPLES * 2> m_float_conversion_buffer;
 
   WaveFileWriter m_wave_writer_dtk;