libascd
libascd is the library that asc uses to communicate with a local
running ASC daemon (ascd). However, since it supplies very general
functionality for communicating with an ASC daemon, libascd can be
used by small utility programs, whose purpose may not at all involve
running programs speculatively. For example, the ASC shell (ascsh)
uses libascd to allow humans to access the database an ASC daemon
maintains, or to instruct an ASC daemon to shut down.
In a sense, libascd defines an application protocol that describes
how any asc-like client may communicate with an ASC daemon over its
UNIX control socket. It also describes how common ASC data structures
are serlialized. (As far as I understand it, this is similar in function
to D-Bus, for example.)
This library and the protocol it defines is used "locally" (i.e., on a single host). It is entirely different from the application protocol that ASC daemons use to communicate with each other over the Internet. (That protocol is known as the ASC network protocol.)
libascd messages
A libascd message can be one of the following types:
- a lookup message (sent from a client to a daemon), which specifies some information about a program and represents a request by the client for learning data about that program,
- a store message (sent from a client to a daemon), which allows a client to send learning data about a particular program to a daemon,
- a dump message (sent from a client to a daemon) which instructs a daemon to prepare a complete "dump" of the database it maintains, or
- a quit message (sent from a client to a daemon), which allows a client to instruct the daemon to shut down.
This information is sent as plain ASCII text over the UNIX control socket,
and is simple enough to be human-readable. A message consists of one or
more parts, each separated by a newline. The entire message ends with
a NUL byte. The first part must be one of the following: lookup,
store, dump, or quit, depending on the type of the message.
Then zero or more parts may follow.
Any binary data, if absolutely necessary to send, is encoded using Base64.