== 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.''' [[toc:]] == Requirements * [[matchable]] * [[uuid]] == Bugs and Limitations * There is currently no support for nodes == Source code The code is available in a [[http://hg.upyum.com/hardwood|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 ==== monitor-ref? (monitor-ref? OBJ) Whether {{obj}} is a monitor reference or not. ==== pid? (pid? OBJ) Whether {{obj}} is a {{pid}} object or not. ==== process-exist? (process-exist? PID) Whether {{pid}} is a running process or not. ==== timeout-condition? (timeout-condition? OBJ) Whether {{obj}} is {{timeout-condition}} or not. === Fundamental Operations ==== spawn (spawn PROC . ARGS) Create a process running {{(proc args ...)}} and returns its {{pid}}. ==== self (self) Return the current process' {{pid}}. ==== setup-thread (setup-thread THREAD) {{Thread}} must be a srfi-18 thread. Make {{thread}} a hardwood process. ==== make-tag (make-tag) Return a new {{tag}}. Tags are guaranteed to be universally unique. ==== monitor (monitor PID) The calling process starts monitoring the {{pid}} process. Return a monitor reference {{ref}}. If that process exits, either normally or not, the caller process will be informed with a message of the form: {{('DOWN ref 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}} ==== demonitor (demonitor ref) Stop the monitor associated with {{ref}}. ==== ! (! PID MSG) Send {{msg}} to process {{pid}}. ==== !! (!! LIST MSG) {{List}} must be a list of pids. Send {{msg}} to all pids in {{list}} ==== ? (? [TIMEOUT [DEFAULT]]) Fetch the first message from the mailbox. ==== ?? (?? PRED [TIMEOUT [DEFAULT]]) Fetch the next message that matches {{pred}}. ==== !? (!? 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 (recv PAT [...] [(after TIMEOUT TMO-ACTION)]) Match incoming messages against {{PAT ...}}. Each pattern must be a valid pattern for '''[[/egg/matchable|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 pid (spawn (lambda () (recv (x (/ 0))))))) (define ref (monitor pid)) (! pid 'msg) (?) --> ('DOWN ref pid ('condition exn)) == Version History ; 0.3 : Bug fix; `!!` function; spawn accepts procedure arguments; monitor references ; 0.2 : Implement process monitoring ; 0.1 : Initial release == License Copyright (c) 2014, Adrien Ramos 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.