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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
- There is currently no support for nodes
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
Hardwood processes are implemented as simple srfi-18 threads so they behave in the same ways. The name process was chosen as per Erlang's nomenclature.
As a general rule, mutation should be avoided when using hardwood, especially inside messages themselves as there is no copy involved.
TIMEOUT in the following definitions can be (as per srfi-18) either of the following:
- an srfi-18 time object, which represents an absolute point in time
- a number, which represents a relative time in seconds
- #f for no timeout
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.
process-exist?
[procedure] (process-exist? PID)Whether pid is a running process 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.
monitor
[procedure] (monitor PID)Start monitoring the pid process and return pid back.
If it exits, either normally or not, the caller process will be informed with a message of the form:
('DOWN pid reason)
where reason can be one of the following:
- symbol exited
- the process exited normally
- symbol no-process
- the process didn't exist
- list ('condition c)
- the process exited because of condition c
!
[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
Monitoring processes
(define monitored-server (monitor (spawn (lambda () (recv (x (/ 0))))))) (! monitored-server 'msg) (?) --> ('DOWN monitored-server ('condition exn))
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.