From 78c8fcbda16670e597fb1417732f1d4adebb9b37 Mon Sep 17 00:00:00 2001
From: hogliux <fabian.renn@gmail.com>
Date: Tue, 20 Jun 2017 16:09:22 +0100
Subject: [PATCH] VST2 Hosting:  Always ensure that the buffer passed to the
 plug-in has at least the maximum number of channels that the VST2 plug-in
 supports

---
 .../format_types/juce_VSTPluginFormat.cpp     | 67 +++++++++++++++----
 1 file changed, 55 insertions(+), 12 deletions(-)

diff --git a/modules/juce_audio_processors/format_types/juce_VSTPluginFormat.cpp b/modules/juce_audio_processors/format_types/juce_VSTPluginFormat.cpp
index d2b7a25989..329fb48fe7 100644
--- a/modules/juce_audio_processors/format_types/juce_VSTPluginFormat.cpp
+++ b/modules/juce_audio_processors/format_types/juce_VSTPluginFormat.cpp
@@ -864,7 +864,15 @@ struct VSTPluginInstance     : public AudioPluginInstance,
                 dispatch (plugInOpcodeSetSampleFloatType, 0, (pointer_sized_int) vstPrecision, 0, 0);
             }
 
-            tempBuffer.setSize (jmax (1, vstEffect->numInputChannels), samplesPerBlockExpected);
+            auto maxChannels = jmax (1, jmax (vstEffect->numInputChannels, vstEffect->numOutputChannels));
+
+            tmpBufferFloat .setSize (maxChannels, samplesPerBlockExpected);
+            tmpBufferDouble.setSize (maxChannels, samplesPerBlockExpected);
+
+            channelBufferFloat .calloc (static_cast<size_t> (maxChannels));
+            channelBufferDouble.calloc (static_cast<size_t> (maxChannels));
+
+            outOfPlaceBuffer.setSize (jmax (1, vstEffect->numOutputChannels), samplesPerBlockExpected);
 
             if (! isPowerOn)
                 setPower (true);
@@ -891,7 +899,13 @@ struct VSTPluginInstance     : public AudioPluginInstance,
             setPower (false);
         }
 
-        tempBuffer.setSize (1, 1);
+        channelBufferFloat.free();
+        tmpBufferFloat.setSize (0, 0);
+
+        channelBufferDouble.free();
+        tmpBufferDouble.setSize (0, 0);
+
+        outOfPlaceBuffer.setSize (1, 1);
         incomingMidi.clear();
 
         midiEventsToSend.freeEvents();
@@ -909,13 +923,13 @@ struct VSTPluginInstance     : public AudioPluginInstance,
     void processBlock (AudioBuffer<float>& buffer, MidiBuffer& midiMessages) override
     {
         jassert (! isUsingDoublePrecision());
-        processAudio (buffer, midiMessages);
+        processAudio (buffer, midiMessages, tmpBufferFloat, channelBufferFloat);
     }
 
     void processBlock (AudioBuffer<double>& buffer, MidiBuffer& midiMessages) override
     {
         jassert (isUsingDoublePrecision());
-        processAudio (buffer, midiMessages);
+        processAudio (buffer, midiMessages, tmpBufferDouble, channelBufferDouble);
     }
 
     bool supportsDoublePrecisionProcessing() const override
@@ -1462,12 +1476,19 @@ private:
     CriticalSection lock;
     bool wantsMidiMessages = false, initialised = false, isPowerOn = false;
     mutable StringArray programNames;
-    AudioBuffer<float> tempBuffer;
+    AudioBuffer<float> outOfPlaceBuffer;
+
     CriticalSection midiInLock;
     MidiBuffer incomingMidi;
     VSTMidiEventList midiEventsToSend;
     VstTimingInformation vstHostTime;
 
+    AudioBuffer<float> tmpBufferFloat;
+    HeapBlock<float*> channelBufferFloat;
+
+    AudioBuffer<double> tmpBufferDouble;
+    HeapBlock<double*> channelBufferDouble;
+
     static pointer_sized_int handleCanDo (const char* name)
     {
         static const char* canDos[] = { "supplyIdle",
@@ -1648,9 +1669,12 @@ private:
 
     //==============================================================================
     template <typename FloatType>
-    void processAudio (AudioBuffer<FloatType>& buffer, MidiBuffer& midiMessages)
+    void processAudio (AudioBuffer<FloatType>& buffer, MidiBuffer& midiMessages,
+                       AudioBuffer<FloatType>& tmpBuffer,
+                       HeapBlock<FloatType*>& channelBuffer)
     {
-        auto numSamples = buffer.getNumSamples();
+        auto numSamples  = buffer.getNumSamples();
+        auto numChannels = buffer.getNumChannels();
 
         if (initialised)
         {
@@ -1729,7 +1753,26 @@ private:
 
             _clearfp();
 
-            invokeProcessFunction (buffer, numSamples);
+            // always ensure that the buffer is at least as large as the maximum number of channels
+            auto maxChannels = jmax (vstEffect->numInputChannels, vstEffect->numOutputChannels);
+            auto channels = channelBuffer.getData();
+
+            if (numChannels < maxChannels)
+            {
+                if (numSamples > tmpBuffer.getNumSamples())
+                    tmpBuffer.setSize (tmpBuffer.getNumChannels(), numSamples);
+
+                tmpBuffer.clear();
+            }
+
+            for (int ch = 0; ch < maxChannels; ++ch)
+                channels[ch] = (ch < numChannels ? buffer.getWritePointer (ch) : tmpBuffer.getWritePointer (ch));
+
+            {
+                AudioBuffer<FloatType> processBuffer (channels, maxChannels, numSamples);
+
+                invokeProcessFunction (processBuffer, numSamples);
+            }
         }
         else
         {
@@ -1757,14 +1800,14 @@ private:
         }
         else
         {
-            tempBuffer.setSize (vstEffect->numOutputChannels, sampleFrames);
-            tempBuffer.clear();
+            outOfPlaceBuffer.setSize (vstEffect->numOutputChannels, sampleFrames);
+            outOfPlaceBuffer.clear();
 
             vstEffect->processAudioFunction (vstEffect, buffer.getArrayOfWritePointers(),
-                                             tempBuffer.getArrayOfWritePointers(), sampleFrames);
+                                             outOfPlaceBuffer.getArrayOfWritePointers(), sampleFrames);
 
             for (int i = vstEffect->numOutputChannels; --i >= 0;)
-                buffer.copyFrom (i, 0, tempBuffer.getReadPointer (i), sampleFrames);
+                buffer.copyFrom (i, 0, outOfPlaceBuffer.getReadPointer (i), sampleFrames);
         }
     }