mailbox

  1. mailbox
    1. Description
    2. Author
    3. Requirements
    4. Download
    5. Documentation
    6. Example
    7. Changelog
    8. License

Description

Thread-safe queues with timeout

Author

felix winkelmann and Kon Lovett

Requirements

None

Download

mailbox.egg

Documentation

[procedure] (make-mailbox [NAME])

Returns a new mailbox object. NAME is an optional name for this mailbox and defaults to some gensym'd symbol.

[procedure] (mailbox? OBJECT)

Is the OBJECT a mailbox?

[procedure] (mailbox-name MAILBOX)

Returns the name of the MAILBOX.

[procedure] (mailbox-empty? MAILBOX)

If there is no data waiting to be transmitted in the MAILBOX, then this procedure returns #t, otherwise it returns #f.

[procedure] (mailbox-timeout-exception? OBJECT)

Is the OBJECT a mailbox timeout exception?

A mailbox timeout exception is a composite condition of 'exn, 'mailbox, and 'timeout, with properties of 'location and 'arguments.

[procedure] (mailbox-send! MAILBOX X)

Stores the data object X. If any threads exist that are waiting for input on MAILBOX, the execution of the first one will be resumed. The data will be read out of a mailbox in the same order in which is written in (in FIFO manner).

[procedure] (mailbox-receive! MAILBOX [TIMEOUT-SECONDS [TIMEOUT-DEFAULT]])

If there is any data in the MAILBOX, then the first object will be removed and returned as the result. If the mailbox is currently empty, the current thread will suspended until data is available.

Should a timeout be specified and occur the TIMEOUT-DEFAULT will be returned. Otherwise a mailbox timeout exception will be signaled for the calling thread.

The TIMEOUT-DEFAULT value cannot be (void).

[procedure] (mailbox-wait! MAILBOX [TIMEOUT-SECONDS])

Similar to mailbox-receive!, but does not remove the received result from the queue of pending data.

Should a timeout be specified and occur a mailbox timeout exception will be signaled for the calling thread.

[procedure] (mailbox-push-back! MAILBOX ITEM)

Pushes an item into the first position of a mailbox.

[procedure] (mailbox-push-back-list! MAILBOX LIST)

Pushes the items in item-list back into the mailbox, so that (car LIST) becomes the next receivable item.

[procedure] (make-mailbox-cursor MAILBOX)

Returns an object which can enumerate a mailbox.

Multiple cursors can scan, and mutate, the same mailbox.

[procedure] (mailbox-cursor? OBJECT)

Is the OBJECT a mailbox-cursor?

[procedure] (mailbox-cursor-mailbox MAILBOX-CURSOR)

Returns the mailbox object associated with the mailbox cursor.

[procedure] (mailbox-cursor-next MAILBOX-CURSOR [TIMEOUT-SECONDS [TIMEOUT-DEFAULT]])

Returns the next object in the mailbox queue, waiting if necessary.

The mailbox queue is scanned from oldest to newest.

Should a timeout be specified and occur the TIMEOUT-DEFAULT will be returned. Otherwise a mailbox timeout exception will be signaled for the calling thread.

The TIMEOUT-DEFAULT value cannot be (void).

[procedure] (mailbox-cursor-rewind MAILBOX-CURSOR)

Position the cursor at the oldest message in the mailbox.

[procedure] (mailbox-cursor-extract-and-rewind MAILBOX-CURSOR)

Remove from the associated mailbox queue the last object returned by mailbox-cursor-next and position the cursor at the oldest message in the mailbox.

The extraction is not performed without a previous call to mailbox-cursor-next.

Example

(require-extension mailbox)

(define (consumer ch)
  (make-thread
    (lambda ()
      (let loop () 
        (print (current-thread) ": reading " (mailbox-receive! ch))
        (loop) ) ) ) )

(define ch (make-mailbox))
(thread-start! (consumer ch))
(for-each
  (lambda (x)
    (print (current-thread) ": writing " x)
    (mailbox-send! ch x) )
  '(33 44 55 hello) )

Changelog

License

 Copyright (c) 2003, Felix L. Winkelmann
 All rights reserved.
 
 Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following
 conditions are met:
 
   Redistributions of source code must retain the above copyright notice, this list of conditions and the following
     disclaimer. 
   Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following
     disclaimer in the documentation and/or other materials provided with the distribution. 
   Neither the name of the author nor the names of its contributors may be used to endorse or promote
     products derived from this software without specific prior written permission. 
 
 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS
 OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY
 AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR
 CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
 SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR
 OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 POSSIBILITY OF SUCH DAMAGE.