diff --git a/src/SharpCompress/Compressors/Rar/UnpackV2017/Unpack.cs b/src/SharpCompress/Compressors/Rar/UnpackV2017/Unpack.cs
index fdcd0df6..54c877e7 100644
--- a/src/SharpCompress/Compressors/Rar/UnpackV2017/Unpack.cs
+++ b/src/SharpCompress/Compressors/Rar/UnpackV2017/Unpack.cs
@@ -30,6 +30,15 @@ namespace SharpCompress.Compressors.Rar.UnpackV2017
             }
         }
 
+        private int UnpIO_UnpRead(byte[] buf, int offset, int count) {
+            // NOTE: caller has logic to check for -1 for error we throw instead.
+            return this.readStream.Read(buf, offset, count);
+        }
+
+        private void UnpIO_UnpWrite(byte[] buf, size_t offset, uint count) {
+            this.writeStream.Write(buf, checked((int)offset), checked((int)count));
+        }
+
         public void DoUnpack(FileHeader fileHeader, Stream readStream, Stream writeStream)
         {
             // as of 12/2017 .NET limits array indexing to using a signed integer
@@ -95,6 +104,7 @@ namespace SharpCompress.Compressors.Rar.UnpackV2017
         public static byte[] EnsureCapacity(byte[] array, int length) {
             return array.Length < length ? new byte[length] : array;
         }
+
     }
 }
 #endif
\ No newline at end of file
diff --git a/src/SharpCompress/Compressors/Rar/UnpackV2017/Unpack.unpack50_cpp.cs b/src/SharpCompress/Compressors/Rar/UnpackV2017/Unpack.unpack50_cpp.cs
index b5eda3de..b362dae0 100644
--- a/src/SharpCompress/Compressors/Rar/UnpackV2017/Unpack.unpack50_cpp.cs
+++ b/src/SharpCompress/Compressors/Rar/UnpackV2017/Unpack.unpack50_cpp.cs
@@ -258,7 +258,7 @@ bool UnpReadBuf()
     DataSize=ReadTop;
   int ReadCode=0;
   if (BitInput.MAX_SIZE!=DataSize)
-    ReadCode=UnpIO->UnpRead(Inp.InBuf+DataSize,BitInput.MAX_SIZE-DataSize);
+    ReadCode=UnpIO_UnpRead(Inp.InBuf,DataSize,BitInput.MAX_SIZE-DataSize);
   if (ReadCode>0) // Can be also -1.
     ReadTop+=ReadCode;
   ReadBorder=ReadTop-30;
@@ -359,7 +359,7 @@ void UnpWriteBuf()
           Filters[I].Type=FILTER_NONE;
 
           if (OutMem!=null)
-            UnpIO->UnpWrite(OutMem,BlockLength);
+            UnpIO_UnpWrite(OutMem,0,BlockLength);
 
           UnpSomeRead=true;
           WrittenFileSize+=BlockLength;
@@ -549,7 +549,7 @@ void UnpWriteData(byte[] Data, size_t offset, size_t Size)
   int64 LeftToWrite=DestUnpSize-WrittenFileSize;
   if ((int64)WriteSize>LeftToWrite)
     WriteSize=(size_t)LeftToWrite;
-  UnpIO->UnpWrite(Data, offset, WriteSize);
+  UnpIO_UnpWrite(Data, offset, WriteSize);
   WrittenFileSize+=Size;
 }