31.6. Generic streams

31.6. Generic streams
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This interface is CLISP-specific and now obsolete. Please use the Gray streams interface instead.

Generic streams are user programmable streams. The programmer interface:

(gstream:make-generic-stream controller): returns a generic stream.
(gstream:generic-stream-controller stream): returns a private object to which generic stream methods dispatch. The typical usage is to retrieve the object originally provided by the user in gstream:make-generic-stream.
(gstream:generic-stream-p stream): determines whether a stream is a generic stream, returning T if it is, NIL otherwise.

In order to specify the behavior of a generic stream, the user must define CLOS methods on the following CLOS generic functions. The function gstream:generic-stream-x corresponds to the Common Lisp function x. They all take a controller and some number of arguments.

(gstream:generic-stream-read-char controller): Returns and consumes the next character, NIL at end of file. Takes one argument, the controller object.
(gstream:generic-stream-peek-char controller): Returns the next character, NIL at end of file. A second value indicates whether the side effects associated with consuming the character were executed: T means that a full READ-CHAR was done, NIL means that no side effects were done. Takes one argument, the controller object.
(gstream:generic-stream-read-byte controller): Returns and consumes the next integer, NIL at end of file. Takes one argument, the controller object.
(gstream:generic-stream-read-char-will-hang-p controller): This generic function is used to query the stream's input status. It returns NIL if gstream:generic-stream-read-char and gstream:generic-stream-peek-char will certainly return immediately. Otherwise it returns true.
(gstream:generic-stream-write-char controller char): The first argument is the controller object. The second argument is the character to be written.
(gstream:generic-stream-write-byte controller by): The first argument is the controller object. The second argument is the integer to be written.
(gstream:generic-stream-write-string controller string start length): Writes the subsequence of string starting from start of length length. The first argument is the controller object.
(gstream:generic-stream-clear-input controller) (gstream:generic-stream-clear-output controller) (gstream:generic-stream-finish-output controller) (gstream:generic-stream-force-output controller) (gstream:generic-stream-close controller): Take one argument, the controller object.

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