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1 | /*
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2 | MIT License http://www.opensource.org/licenses/mit-license.php
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3 | Author Tobias Koppers @sokra
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4 | */
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5 |
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6 | "use strict";
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7 |
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8 | /**
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9 | * @template T
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10 | * @template {Error} E
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11 | * @param {Iterable<T>} items initial items
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12 | * @param {number} concurrency number of items running in parallel
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13 | * @param {function(T, function(T): void, function(E=): void): void} processor worker which pushes more items
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14 | * @param {function(E=): void} callback all items processed
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15 | * @returns {void}
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16 | */
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17 | const processAsyncTree = (items, concurrency, processor, callback) => {
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18 | const queue = Array.from(items);
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19 | if (queue.length === 0) return callback();
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20 | let processing = 0;
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21 | let finished = false;
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22 | let processScheduled = true;
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23 |
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24 | const push = item => {
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25 | queue.push(item);
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26 | if (!processScheduled && processing < concurrency) {
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27 | processScheduled = true;
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28 | process.nextTick(processQueue);
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29 | }
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30 | };
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31 |
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32 | const processorCallback = err => {
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33 | processing--;
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34 | if (err && !finished) {
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35 | finished = true;
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36 | callback(err);
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37 | return;
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38 | }
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39 | if (!processScheduled) {
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40 | processScheduled = true;
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41 | process.nextTick(processQueue);
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42 | }
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43 | };
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44 |
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45 | const processQueue = () => {
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46 | if (finished) return;
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47 | while (processing < concurrency && queue.length > 0) {
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48 | processing++;
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49 | const item = queue.pop();
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50 | processor(item, push, processorCallback);
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51 | }
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52 | processScheduled = false;
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53 | if (queue.length === 0 && processing === 0 && !finished) {
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54 | finished = true;
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55 | callback();
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56 | }
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57 | };
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58 |
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59 | processQueue();
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60 | };
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61 |
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62 | module.exports = processAsyncTree;
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