From dea2a8eb9cc34fa4ddcb86f0954985ba7f90a17a Mon Sep 17 00:00:00 2001
From: "Dane Z. Bush" <danebush45@yahoo.com>
Date: Sun, 13 Jan 2019 04:00:45 -0500
Subject: [PATCH] Check for null reference before callback

During high-speed usage, callbacks will throw a null-reference error because the object has been deleted or collected before the callback can be executed on it. Add checks to see if the object is still valid.
---
 Source/SharpDX.XAudio2/VoiceShadow.cs | 32 ++++++++++++++++++++++++++-
 1 file changed, 31 insertions(+), 1 deletion(-)

diff --git a/Source/SharpDX.XAudio2/VoiceShadow.cs b/Source/SharpDX.XAudio2/VoiceShadow.cs
index 85a8e8184..f925ce7e5 100644
--- a/Source/SharpDX.XAudio2/VoiceShadow.cs
+++ b/Source/SharpDX.XAudio2/VoiceShadow.cs
@@ -64,35 +64,57 @@ public VoiceVtbl()
             static private void OnVoiceProcessingPassStartImpl(IntPtr thisObject, int bytes)
             {
                 var shadow = ToShadow<VoiceShadow>(thisObject);
+                if (shadow == null)
+                    return;
                 var callback = (VoiceCallback)shadow.Callback;
+                if (callback == null)
+                    return;
                 callback.OnVoiceProcessingPassStart(bytes);
+              
             }
 
             static private void OnVoiceProcessingPassEndImpl(IntPtr thisObject)
             {
                 var shadow = ToShadow<VoiceShadow>(thisObject);
+                if (shadow == null)
+                    return;
                 var callback = (VoiceCallback)shadow.Callback;
+                if (callback == null)
+                    return;
                 callback.OnVoiceProcessingPassEnd();
+
             }
 
             static private void OnStreamEndImpl(IntPtr thisObject)
             {
                 var shadow = ToShadow<VoiceShadow>(thisObject);
+                if (shadow == null)
+                    return;
                 var callback = (VoiceCallback)shadow.Callback;
+                if (callback == null)
+                    return;
                 callback.OnStreamEnd();
             }
 
             static private void OnBufferStartImpl(IntPtr thisObject, IntPtr address)
             {
                 var shadow = ToShadow<VoiceShadow>(thisObject);
+                if (shadow == null)
+                    return;
                 var callback = (VoiceCallback)shadow.Callback;
+                if (callback == null)
+                    return;
                 callback.OnBufferStart(address);
             }
 
             static private void OnBufferEndImpl(IntPtr thisObject, IntPtr address)
             {
                 var shadow = ToShadow<VoiceShadow>(thisObject);
+                if (shadow == null)
+                    return;
                 var callback = (VoiceCallback)shadow.Callback;
+                if (callback == null)
+                    return;
                 callback.OnBufferEnd(address);
             }
 
@@ -100,14 +122,22 @@ static private void OnBufferEndImpl(IntPtr thisObject, IntPtr address)
             static private void OnLoopEndImpl(IntPtr thisObject, IntPtr address)
             {
                 var shadow = ToShadow<VoiceShadow>(thisObject);
+                if (shadow == null)
+                    return;
                 var callback = (VoiceCallback)shadow.Callback;
+                if (callback == null)
+                    return;
                 callback.OnLoopEnd(address);
             }
 
             static private void OnVoiceErrorImpl(IntPtr thisObject, IntPtr bufferContextRef, int error)
             {
                 var shadow = ToShadow<VoiceShadow>(thisObject);
+                if (shadow == null)
+                    return;
                 var callback = (VoiceCallback)shadow.Callback;
+                if (callback == null)
+                    return;
                 callback.OnVoiceError(bufferContextRef, new Result(error));
             }
         }
@@ -117,4 +147,4 @@ protected override CppObjectVtbl GetVtbl
             get { return Vtbl; }
         }
     }
-}
\ No newline at end of file
+}