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133 lines
3.1 KiB
133 lines
3.1 KiB
/**
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* An async collection / item stream.
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* @param {Array} from Optional array to begin reading from.
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*/
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function Stage(from) {
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var base = this;
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this.array = from || [];
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this.over = false;
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this.acceptInvalid = false;
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var next = {
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waiters: [],
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wait: function() {
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return new Promise(resolve => next.waiters.push(function() { resolve(); }));
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},
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signal: function() {
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if(next.waiters.length>0) {
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next.waiters.shift()();
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}
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},
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flush: function() {
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while(next.waiters.length>0) {
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next.waiters.shift()();
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}
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}
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};
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/**
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* Returns true if there are any values left in the stream, or if the stream is still open.
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*/
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this.hasValues = () => {
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return !(base.over && base.array.length==0);
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};
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/**
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* Take one item off then end. Function will yield if none available to produce yet.
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* @return {} undefined if there is no more items to produce (`commit` was called), otherwise the next item in the stream.
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*/
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this.take = async function() {
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if(base.over && base.array.length<=0)
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return undefined;
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if(base.array.length<=0)
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await next.wait();
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if(base.over && base.array.length<=0)
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return undefined;
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return base.array.shift();
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};
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/**
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Get all current items not yet produced.
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*/
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this.poll = function() {
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return base.array;
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};
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/**
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* Take without blocking. Returns `null` if there are no items to take.
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*/
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this.takeNB = function() {
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if(base.array.length<=0)
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return null;
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return base.array.shift();
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};
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/**
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* Await and take the rest of the items in this stream until `commit` is called.
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*/
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this.swallow0 = async function() {
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var ar = [];
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var token;
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while((token = await base.take())) {
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ar.push(token);
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}
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return ar;
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};
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/**
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* Returns a promise that resolves to `swallow0`. Optionally takes a timeout that will reject the promise if it does not complete before the stream is closed with `commit`.
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*/
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this.swallow = function(timeout) {
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if(!timeout) return base.swallow0();
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else {
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return new Promise(function(_resolve,_reject) {
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var running=true;
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var resolve = function(v) {
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if(running) _resolve(v);
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running=false;
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};
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var reject= function(v) {
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if(running) _reject(v);
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running=false;
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};
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base.swallow0().then(resolve);
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if(timeout>0)
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setTimeout(()=> reject(new Error("swallow timeout reached ("+timeout+")")), timeout);
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});
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}
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};
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/**
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* Send a collection of values to the stream.
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*/
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this.giveMany= function(values) {
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for(let value of values)
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base.give(value);
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};
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/**
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* Send a single value to the stream
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*/
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this.give = function(value) {
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if(!value && !base.acceptInvalid)
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return;
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base.array.push(value);
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next.signal();
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};
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/**
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* Close the stream. After this is called, once all elements already in the stream have been consumed, `take` will resolve immediately to `undefined` for any more consumers. It cannot be opened again.
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*/
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this.commit = function() {
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base.over = true;
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next.flush();
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return base;
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};
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};
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if(module)
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module.exports = Stage;
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