peekByteOff

Read a value from a memory location given by a base address and offset. The following equality holds:
peekByteOff addr off = peek (addr `plusPtr` off)
Get the current ByteOffset in the input byte sequence of the Decoder. The Decoder does not provide any facility to get at the input data directly (since that is tricky with an incremental decoder). The next best is this primitive which can be used to keep track of the offset within the input bytes that makes up the encoded form of a term. By keeping track of the byte offsets before and after decoding a subterm (a pattern captured by decodeWithByteSpan) and if the overall input data is retained then this is enables later retrieving the span of bytes for the subterm.
Read the variable from a given pointer.
Read the variable from a given pointer.
Read the element at a given offset. Additional information about the offests of the subfields are needed.
Peek the type based on the tag.
View the variable under a pointer, with offset.