A character input stream can be created by defining a class that includes fundamental-character-input-stream and defining methods for the following generic functions.
stream-read-char Generic Function
stream-read-char stream
Summary: Reads one character from stream, and returns either a character object or the symbol :eof if the stream is at end-of-file. There is no default method for this generic function, so every subclass of fundamental-character-input-stream must define a method.
stream-unread-char Generic Function
stream-unread-char stream character
Summary: Undoes the last call to stream-read-char, as in unread-char, and returns nil. There is no default method for this, so every subclass of fundamental- character-input-stream must define a method.
stream-read-char-no-hang Generic Function
stream-read-char-no-hang stream
Summary: Returns either a character, or nil if no input is currently available, or :eof if end-of-file is reached. This is used to implement read-char-no-hang. The default method provided by fundamental-character-input-stream simply calls stream-read-char; this is sufficient for file streams, but interactive streams should define their own method.
stream-peek-char Generic Function
stream-peek-char stream
Summary: Returns either a character or :eof without removing the character from the stream's input buffer. This is used to implement peek-char; this corresponds to peek-type of nil. The default method calls stream-read-char and stream-unread-char.
stream-listen Generic Function
stream-listen stream
Summary: Returns t if there is any input pending on stream; otherwise, it returns nil. This is used by listen. The default method uses stream-read-char-no-hang and stream-unread-char. Most streams should define their own method, as it will usually be trivial and will generally be more efficient than the default method.
stream-read-line Generic Function
stream-read-line stream
Summary: Returns a string as the first value, and t as the second value if the string was terminated by end-of-file instead of the end of a line. This is used by read-line. The default method uses repeated calls to stream-read-char.
stream-clear-input Generic Function
stream-clear-input stream
Summary: Clears any buffered input associated with stream, and returns nil. This is used to implement clear-input. The default method does nothing.
CLIM 2.0 User Guide - 01 Dec 2021 19:39:02