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pipe.js
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pipe.js
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/**
* Pipe calls the same function with different parameters;
* it allows for asynchronous but single threaded activity.
*
* action has a profile:
* action(param_array_element, this.static_params, this._act_done_callback, this._pipe_done_callback);
*
* note that the last two parameters are functions PRODUCED by local functions.
*/
function Pipe(callback, action, param_array, static_params) {
this.callback = callback;
if (typeof action != 'function') {
throw new Error(__filename + ': non function passed as action');
}
if (typeof callback != 'function') {
throw new Error(__filename + ': non function passed as callback');
}
this.action = action;
this.param_array = param_array ? param_array : [];
this.stop_on_end_of_param_array = false;
this.static_params = static_params ? static_params : false;
this.idle = true;
this.done = false;
this.iv = null;
}
module.exports = Pipe;
Pipe.prototype = {
_iv: function() {
var self = this;
return function() {
self.check_pipe();
};
},
start: function() {
var self = this;
this._pipe_done_callback = function() {
// console.log('pipe done callback called');
self.finish();
};
this._act_done_callback = function(){
// console.log('act done callback called');
self.act();
}
this.act();
},
check_pipe: function() {
if (this.idle) {
this.idle = false;
// console.log('acting');
this.act();
}
},
/**
* Pipe allows for an array of changing parameters,passed in param_array
* -- howver they are optional.
* The param_array running out of params
* doesn't trigger finish unless stop_on_end_of_param_array is set to true.
* If not, then stopping the loop has to be done inside action
* by calling pipe.finish(); this is why pipe is the first parameter
* of action.
*/
act: function() {
if (this.param_array.length) {
var params = this.param_array.shift();
} else if (this.stop_on_end_of_param_array) {
// console.log('out of params - finishing');
return this.finish();
} else {
params = false;
}
// console.log('acting on ', params, this.static_params);
this.action(params, this.static_params, this._act_done_callback, this._pipe_done_callback);
},
_act_done_callback: false,
_pipe_done_callback: false,
/**
* Finish will prevent further functions from being launched.
* It won't abort the execution of a function being executied.
*/
finish: function() {
this.callback(this);
this.done = true;
}
}