Use Stream extension to ensure read operations return the requested number of bytes (unless EOF arrives first).

Adler32Context.cs

@@ -334,12 +334,12 @@ public sealed class Adler32Context : IChecksum
         ushort localSum2 = 0;
 
         var buffer = new byte[65536];
-        int read   = fileStream.Read(buffer, 0, 65536);
+        int read   = fileStream.EnsureRead(buffer, 0, 65536);
 
         while(read > 0)
         {
             Step(ref localSum1, ref localSum2, buffer, (uint)read, useNative, nativeContext);
-            read = fileStream.Read(buffer, 0, 65536);
+            read = fileStream.EnsureRead(buffer, 0, 65536);
         }
 
         var finalSum = (uint)((localSum2 << 16) | localSum1);