RFC 1014 (rfc1014) - Page 2 of 20
XDR: External Data Representation standard
Alternative Format: Original Text Document
RFC 1014 External Data Representation June 1987 residual zero bytes, r, to make the total byte count a multiple of 4. We include the familiar graphic box notation for illustration and comparison. In most illustrations, each box (delimited by a plus sign at the 4 corners and vertical bars and dashes) depicts a byte. Ellipses (...) between boxes show zero or more additional bytes where required. +--------+--------+...+--------+--------+...+--------+ | byte 0 | byte 1 |...|byte n-1| 0 |...| 0 | BLOCK +--------+--------+...+--------+--------+...+--------+ |<-----------n bytes---------->|<------r bytes------>| |<-----------n+r (where (n+r) mod 4 = 0)>----------->| 3. XDR DATA TYPES Each of the sections that follow describes a data type defined in the XDR standard, shows how it is declared in the language, and includes a graphic illustration of its encoding. For each data type in the language we show a general paradigm declaration. Note that angle brackets (< and >) denote variablelength sequences of data and square brackets ([ and ]) denote fixed-length sequences of data. "n", "m" and "r" denote integers. For the full language specification and more formal definitions of terms such as "identifier" and "declaration", refer to section 5: "The XDR Language Specification". For some data types, more specific examples are included. A more extensive example of a data description is in section 6: "An Example of an XDR Data Description". 3.1 Integer An XDR signed integer is a 32-bit datum that encodes an integer in the range [-2147483648,2147483647]. The integer is represented in two's complement notation. The most and least significant bytes are 0 and 3, respectively. Integers are declared as follows: int identifier; (MSB) (LSB) +-------+-------+-------+-------+ |byte 0 |byte 1 |byte 2 |byte 3 | INTEGER +-------+-------+-------+-------+ <------------32 bits------------> SUN Microsystems
