The RenderMan Interface - Paul Bourke

In the following sections the syntax for each encoding is presented as a sequence of bytes
separated by ‘|’ symbols. Numeric values should interpreted as octal values (base 8) if
they have a leading ‘0’ digit, otherwise as decimal values. Items shown in angle brackets
‘< >’ represent varying items, such as a numeric value or string that is being encoded.
Integers and fixed-point numbers. Integer and fixed-point values can be transmitted in
2-5 bytes. The encoded token has the form:
0200 + (d · 4) + w |
where the next w + 1 bytes form a signed integer taken from the most significant byte to
the least significant byte, and the bottom d bytes are after the decimal point.
Strings. Strings shorter than 16 bytes, say w bytes, can be transmitted with a prefixing
token:
0220 + w |
Other strings must use a prefixing token followed by a variable length string length, and
then followed by the string itself:
0240 + l | |
where l + 1 is the number of bytes needed to specify the length of the string, 0 ≤ l ≤ 3. The
string length is an unsigned value and is transmitted from most significant byte to least
significant byte. Unlike unencoded strings, there are no escape or special characters in an
encoded string.
Defining strings. For strings that are to be transmitted repeatedly, a string token can be
defined with:
0315 + w | |
where w + 1 is the number of bytes needed to specify the token, (1 or 2), and the string
being defined is transmitted in an encoded or unencoded form. The token is an unsigned
value and is transmitted from most significant byte to least significant byte. For efficiency,
the range of tokens defined should be as compact as possible.
Referencing defined strings. To interpolate a string that has previously been defined (as
described above), the following is used:
0317 + w |
where the token refers to the string to be interpolated.
Floating-point values. Floating-point values are transmitted in single-precision or doubleprecision
IEEE format from most significant byte to least significant byte. Single-precision
floating-point values occupy four bytes in the input stream and double-precision values
occupy eight bytes.
Floating point arrays. Aggregates of single-precision floating-point values can be transmitted
with a prefixing token byte. Variable sized arrays are transmitted as a token byte
followed by a variable length array size, and then followed by the array itself:
0310 + l | |
The array length is an unsigned value, l + 1 bytes long, and is transmitted from most
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