49 lines
1.1 KiB
JavaScript
49 lines
1.1 KiB
JavaScript
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'use strict';
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var toPosInt = require('es5-ext/number/to-pos-integer')
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, create = Object.create, hasOwnProperty = Object.prototype.hasOwnProperty;
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module.exports = function (limit) {
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var size = 0, base = 1, queue = create(null), map = create(null), index = 0, del;
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limit = toPosInt(limit);
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return {
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hit: function (id) {
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var oldIndex = map[id], nuIndex = ++index;
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queue[nuIndex] = id;
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map[id] = nuIndex;
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if (!oldIndex) {
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++size;
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if (size <= limit) return;
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id = queue[base];
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del(id);
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return id;
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}
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delete queue[oldIndex];
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if (base !== oldIndex) return;
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while (!hasOwnProperty.call(queue, ++base)) continue; //jslint: skip
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},
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delete: del = function (id) {
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var oldIndex = map[id];
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if (!oldIndex) return;
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delete queue[oldIndex];
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delete map[id];
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--size;
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if (base !== oldIndex) return;
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if (!size) {
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index = 0;
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base = 1;
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return;
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}
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while (!hasOwnProperty.call(queue, ++base)) continue; //jslint: skip
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},
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clear: function () {
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size = 0;
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base = 1;
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queue = create(null);
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map = create(null);
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index = 0;
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}
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};
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};
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