tart-host/index.js

Tart core scheduling

/*

index.js - "tart-host": Actor-based core scheduling for guest configurations

The MIT License (MIT)

Copyright (c) 2013 Dale Schumacher

Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documentation
files (the "Software"), to deal in the Software without
restriction, including without limitation the rights to use,
copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following
conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.

*/
"use strict";

var host = module.exports;

/*
Default exception handler simply throws the exception.
*/
host.defaultFail = function fail(exception) {
    throw exception;
};

/*
Default error logger simply writes to the console.
*/
host.errorLog = function log(message) {
    console.log(message);
};

/*
Create an actor behavior that calls a synchronous object method
using `message.arguments` as the argument list
and sending the return value to `message.ok`.
If an exception is thrown, it is sent to `message.fail`.
*/
host.adapter = function adapter(obj, fn) {
    return function applyBeh(message) {
        var ok = message.ok;
        var fail = message.fail || host.defaultFail;
        try {
            ok(fn.apply(obj, message.arguments));
        } catch (ex) {
            fail(ex);
        }
    };
};

/*
Create an actor behavior that cycles through a list of guest configurations,
dispatching one event at a time until no events remain.
*/
host.dispatchRing = function dispatchRing(guests, errorLog) {
    errorLog = errorLog || host.errorLog;
    var m = guests.length;
    var n = m;  // countdown to idle
    var i = 0;  // current guest index
    var dispatchBeh = function dispatchBeh() {
        var self = this.self;
        var fail = function fail(ex) {
            errorLog(ex);
            self(false);  // treat exception as no events
        };
        var guest = guests[i];
        guest({
            arguments: [],
            ok: self,
            fail: fail
        });
        this.behavior = effectBeh;  // wait for dispatch effect
    };
    var effectBeh = function effectBeh(effect) {
        if (effect) {
            n = m;  // reset idle countdown
        } else {
            --n;  // countdown idle guests
        }
        if (n > 0) {
            ++i;  // advance to next guest
            if (i >= m) {
                i = 0;
            }
            this.behavior = dispatchBeh;  // dispatch next event
            this.self();
        }
    };
    return dispatchBeh;
};

/*
Create an actor behavior that cycles through a list of guest configurations,
calling `eventLoop(options)` for each until all event queues are exhausted.
*/
host.eventLoopRing = function eventLoopRing(guests, errorLog) {
    errorLog = errorLog || host.errorLog;
    var m = guests.length;
    var n = m;  // countdown to idle
    var i = 0;  // current guest index
    var dispatchBeh = function dispatchBeh() {
        var self = this.self;
        var fail = function fail(ex) {
            errorLog(ex);
            self(true);  // treat exception as queue empty
        };
        var guest = guests[i];
        guest.eventLoop({
            arguments: [ guest.options ],
            ok: self,
            fail: fail
        });
        this.behavior = statusBeh;  // wait for eventLoop status
    };
    var statusBeh = function statusBeh(empty) {
        if (empty) {
            --n;  // countdown idle guests
        } else {
            n = m;  // reset idle countdown
        }
        if (n > 0) {
            ++i;  // advance to next guest
            if (i >= m) {
                i = 0;
            }
            this.behavior = dispatchBeh;  // dispatch next event
            this.self();
        }
    };
    return dispatchBeh;
};