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hardwood

Erlang style concurrency for CHICKEN Scheme, heavily inspired by termite.

All the Termite API is currently not implemented and probably never will. Also, some incompatibilities are to be expected.

Requirements

Bugs and Limitations

Source code

The code is available in a mercurial repository

You can clone it with:

hg clone http://hg.upyum.com/hardwood

Author

Adrien Ramos, heavily inspired by the Termite project of Guillaume Germain.

Documentation

Notes

TIMEOUT in the following definitions can be (as per srfi-18) either of the following:

If DEFAULT is specified when TIMEOUT is, it is returned in case of timeout. Otherwise timeout-condition is signaled.

Constants

timeout-condition

Condition object raised when a timeout is reached.

Predicates

timeout-condition?

[procedure] (timeout-condition? OBJ)

Whether OBJ is timeout-condition or not.

pid?

[procedure] (pid? OBJ)

Whether OBJ is a pid object or not.

Fundamental Operations

spawn

[procedure] (spawn THUNK)

Create a process running thunk and returns its pid.

self

[procedure] (self)

Return the current process' pid.

setup-thread

[procedure] (setup-thread THREAD)

Thread must be a srfi-18 thread.

Make thread a hardwood process.

!

[procedure] (! PID MSG)

Send msg to process pid.

?

[syntax] (? [TIMEOUT [DEFAULT]])

Fetch the first message from the mailbox.

??

[procedure] (?? PRED [TIMEOUT [DEFAULT]])

Fetch the next message that matches pred.

make-tag

[procedure] (make-tag)

Return a new tag.

Tags are guaranteed to be universally unique.

!?

[procedure] (!? PID MSG [TIMEOUT [DEFAULT]])

Send msg to process pid and wait for a reply.

The actual message sent to pid is (list (self) tag msg).

This procedure wait for a reply of the form (list tag reply) and returns reply.

recv

[syntax] (recv PAT [...] [(after TIMEOUT TMO-ACTION)])

Match incoming messages against PAT ....

Each pattern must be a valid pattern for match.

Optionally, do tmo-action after timeout.

This version of recv is incompatible with the one defined in the Termite paper and implementation as it uses the syntax of the matchable egg.

Examples

Making the REPL process a hardwood process

Inside csi:

(setup-thread (current-process))

This can be useful to communicate with other processes from the REPL, as in the following examples.

Making a "server" process

(define pong-server
  (spawn
    (lambda ()
      (let loop ()
        (recv
          (((? pid? pid) 'ping)  (! pid 'pong)
                                 (loop))
          (else  (loop))))

(! pong-server (list (self) 'ping))

(?)                 --> pong

Selective message retrieval

(! (self) 1)
(! (self) 2)
(! (self) 3)

(?)                 --> 1
(?? odd?)           --> 3
(?)                 --> 2

RPC service

(define rpc-server
  (spawn
    (lambda ()
      (let loop ()
        (recv
          ((from tag ('add a b))
           (! from (list tag (+ a b)))))
        (loop)))))

(!? rpc-server '(add 21 21))      ---> 42

Version History

0.1
Initial release

License

Copyright (c) 2014, Adrien Ramos <kooda@upyum.com>
All rights reserved.

Redistribution and use in source and binary forms, with or without
modification, are permitted provided that the following conditions are
met:

1. Redistributions of source code must retain the above copyright
notice, this list of conditions and the following disclaimer.

2. 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.

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
HOLDER 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.