device-extend

Generic Function

Package: excl

Arguments: stream need action

Returns true for success, nil for failure, to extend the underlying device allocation and/or connection. The need argument is the number of bytes that will be read or written if the extension is successful, and the action argument describes the operation being performed; typical values for action are :input, :input-check, :output, and :output-check.

Note that Allegro CL offers calls to device-extend for the following circumstances:

string-output-simple-stream: The action argument is always :output or :output-check. If device-extend returns nil, an error is generated.
string-input-simple-stream: The action argument is always :input or :input-check. The primary method on this stream simply returns nil, which causes end-of-file processing to occur.
mapped-file-simple-stream: Read operations pass an :input or :input-check action. A nil return for a read will cause end-of-file processing by the read operation. Writes pass an :output action. If device-extend returns nil, an error is generated.

Defined methods

On class: direct-simple-stream: returns nil.
On class: string-input-simple-stream: returns nil.
On class: string-output-simple-stream: :output allocates and copies a new string twice the current size.
On class: fill-pointer-output-simple-stream: :output extends the array using adjust-array.
On class: mapped-file-simple-stream: returns nil.

See streams.htm for information on the simple-streams implementation in Allegro CL. The older but still supported Gray streams implementation is described in gray-streams.htm.

The documentation is described in introduction.htm and the index is in index.htm.

Created 2000.10.5.