5.11 The STREAMS module
adjust-stream-position
Open generic function
Summary
Moves the position of a positionable stream by a specified amount.
Signature
adjust-stream-position positionable-stream delta #key from => new-position
Arguments
- positionable-stream
-
An instance of
<positionable-stream>. - delta
- An instance of
<integer>. - from
- One of
#"current",#"start", or#"end". Default value:#"current".
Values
- new-position
- An instance of
<stream-position>.
Library
io
Module
streams
Library
io
Module
streams
Description
Moves the position of positionable-stream to be offset delta elements from the position indicated by from. The new position is returned.
When from is #"start", the stream is positioned relative to the beginning of the stream. When from is #"end", the stream is positioned relative to its end. When from is #"current", the current position is used.
Using adjust-stream-position to set the position of a stream to be beyond its current last element causes the underlying aggregate to be grown to a new size. When extending the underlying aggregate for a stream, the contents of the unwritten elements are the fill character for the underlying sequence.
Example
The following example returns a string, the first ten characters of which are the space character, which is the fill character for the sequence <string>.
let stream = make(<string-stream>, direction: #"output"); adjust-stream-position(stream, 10); write(stream, "whoa!"); stream-contents(stream);