CAPS IPC started

Matt Dillon has placed inital IPC support, using a message structure that is described in the extended entry here, taken from his commit message:

“Initial CAPS IPC structural encoding and decoding support. Note that the kernel is uninvolved (other then in supplying the IPC mechanism). After careful consideration I decided that XML was just too much overkill but that a human-readable format is still desireable. The encoding format supports integers, strings, opaque data, arrays, and is extensible and structural.

An example encoding of the struct passwd record for user ‘nobody’:


Class elements include (S)tructure, (F)ield, (D)ata, (A)rray. Data types are free-form numeric (stored as hex), with the source responsible for encoding negative numbers with a ‘-‘, and quoted opaque data (e.g. strings). Any class element may recurse using {}. Structures and Arrays always recurse. Unknown recursions are ignored by the decoder (for future backwards compatibility). Whitespace is allowed but most non-alpha-numeric characters must be %-hex-escaped.

The decoder understands simple integer types, arrays, buffers, embedded sub-structures, and string pointer structural elements. It does not (yet) understand multi-dimensional arrays, sparse element notation, or ** pointers.

This is a nice, compact encoding format that can be used for both packetized messages and persistently-connected streams. The initial commit only supports full-messages, however.”

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