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

CRC64Context.cs

@@ -498,13 +498,13 @@ public sealed class Crc64Context : IChecksum
         ulong[][] localTable = GenerateTable(polynomial);
 
         var buffer = new byte[65536];
-        int read   = fileStream.Read(buffer, 0, 65536);
+        int read   = fileStream.EnsureRead(buffer, 0, 65536);
 
         while(read > 0)
         {
             Step(ref localHashInt, localTable, buffer, (uint)read, useEcma, useNative, nativeContext);
 
-            read = fileStream.Read(buffer, 0, 65536);
+            read = fileStream.EnsureRead(buffer, 0, 65536);
         }
 
         localHashInt ^= seed;