Chapter 2. XDR—External Data Representation

The NFS protocol data in RPC messages must be represented in a format that can be understood by both the sender and the recipient computer. This chapter explains the need for the common data representation provided by XDR, then examines the representation of primitive values such as integers and strings, followed by structured types such as arrays, linked lists, and discriminated unions. The chapter closes with a description of the XDR language: a notation for describing XDR encoded data. This chapter is not intended to be a complete description of all XDR types. For instance, there is no mention of enum and void types, nor of the XDR floating point data types such as float, double, and quadruple. It describes only the data types used by the NFS protocol and related protocols presented in this book. For a more complete description see [Bloomer92], [RFC 1832], or [X/OpenNFS96] in the References section near the end of the book.