XDR defines fixed-length uninterpreted data as opaque.
Fixed-length opaque data is declared as follows:
opaque identifier[n];
The constant n is the static number of bytes
necessary to contain the opaque data. If n is not a multiple
of 4, then the n bytes are followed by enough (0
to 3) residual 0 bytes, r, to make the total byte
count of the opaque object a multiple of 4. See the Fixed-Length
Opaque figure (Figure 1).
Figure 1. Fixed-Length Opaque. This diagram contains 4 lines of information. The second line
of the diagram is the main line, listing bytes as follows: byte 0,
byte 1, dots signifying the bytes between byte 1 and byte n-1.
The next byte is labeled: byte n-1, and is followed by residual
byte 0. Dots signify more residual bytes that end in a final byte
0. The remaining lines of the diagram describe this main line of bytes.
The first line assigns numbers to the bytes as follows: number 0 for
byte 0, number 1 for byte 1, and dots signifying a continuing sequence.
The third line assigns byte values to the bytes in the main line as
follows: byte 0 through byte n-1 yield n bytes. All
the residual bytes together equal r bytes. The fourth line,
which spans the entire diagram, shows the following equation:n+r (where
(n+r) mod 4 = 0).
