anchor.diff:      /// After that call, the characters at and before the span might be freed from memory, so this function must not be used twice.
       let unpinSpanAndGenerate symbol (fPostProcess: CharStreamCallback<'symbol>) cs (CharSpan (idxStart, idxEnd) as csp) =
           if cs.StartingIndex <= idxStart && cs.LengthSoFar > idxEnd then
  -            match cs.Source with
  -            | StaticBlock sb ->
  -                cs.StartingIndex <- idxEnd + 1UL
  -                let length = idxEnd - idxStart + 1UL |> int
  -                let span = sb.Span.Slice(int idxStart, length)
  -                fPostProcess.Invoke(symbol, cs.Position, span), cs.Position
  +            cs.StartingIndex <- idxEnd + 1UL
  +            let length = idxEnd - idxStart + 1UL |> int
  +            let span =
  +                match cs.Source with
  +                | StaticBlock sb -> sb.Span.Slice(int idxStart, length)
  +                | DynamicBlock db -> ReadOnlySpan(db.Buffer).Slice(int <| idxStart - db.BufferStartingIndex, length)
  +            fPostProcess.Invoke(symbol, cs.Position, span), cs.Position
           else
               failwithf "Trying to read the character span %O, from a stream that was last read at %d." csp cs.StartingIndex
   
  
positive.code:     /// [omit]
      member x.LengthSoFar =
          match x with
          | StaticBlock x -> uint64 x.Length
          | DynamicBlock db -> db.BufferEndingIndex + GenericOne
  
  /// A data structure that supports efficient and copy-free access to a read-only sequence of characters.
  /// It is not thread-safe.
  
negative.code:         mutable Buffer: char[]
          /// The index of the first element in the buffer.
          mutable BufferStartingIndex: uint64
          /// The index of the next character to be read.
          mutable NextReadIndex: uint64
      }
      /// The real length of the buffer, excluding the unpinned characters at the end.
      member x.BufferContentLength = x.NextReadIndex - x.BufferStartingIndex |> int
  
  /// A representation of a `CharStream`.
  type private CharStreamSource =
  