65 lines
1.2 KiB
JavaScript
65 lines
1.2 KiB
JavaScript
/* exported createCache */
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'use strict';
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// create a FIFO limit-size map.
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function createCache(size = 1000) {
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const map = new Map();
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const buffer = Array(size);
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let index = 0;
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let lastIndex = 0;
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return {
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get,
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set,
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delete: delete_,
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clear,
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has: id => map.has(id),
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entries: function *() {
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for (const [id, item] of map) {
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yield [id, item.data];
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}
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},
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values: function *() {
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for (const item of map.values()) {
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yield item.data;
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}
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},
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get size() {
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return map.size;
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}
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};
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function get(id) {
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const item = map.get(id);
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return item && item.data;
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}
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function set(id, data) {
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if (map.size === size) {
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// full
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map.delete(buffer[lastIndex].id);
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lastIndex = (lastIndex + 1) % size;
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}
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const item = {id, data, index};
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map.set(id, item);
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buffer[index] = item;
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index = (index + 1) % size;
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}
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function delete_(id) {
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const item = map.get(id);
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if (!item) {
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return;
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}
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map.delete(item.id);
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const lastItem = buffer[lastIndex];
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lastItem.index = item.index;
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buffer[item.index] = lastItem;
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lastIndex = (lastIndex + 1) % size;
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}
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function clear() {
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map.clear();
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index = lastIndex = 0;
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}
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}
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