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Update: Add BoundedCache for Thumbnails Sidebar (box#917)
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Conrad Chan
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Conrad Chan
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Feb 19, 2019
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,62 @@ | ||
| import Cache from './Cache'; | ||
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| class BoundedCache extends Cache { | ||
| /** @property {Array} - Maintains the list of cache keys in order in which they were added to the cache */ | ||
| cacheQueue; | ||
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| /** @property {number} - The maximum number of entries in the cache */ | ||
| maxEntries; | ||
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| /** | ||
| * [constructor] | ||
| * | ||
| * @param {number} [maxEntries] - Override the maximum number of cache entries | ||
| */ | ||
| constructor(maxEntries) { | ||
| super(); | ||
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| this.maxEntries = maxEntries || 500; | ||
| this.cache = {}; | ||
| this.cacheQueue = []; | ||
| } | ||
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| /** | ||
| * Destroys the bounded cache | ||
| * | ||
| * @return {void} | ||
| */ | ||
| destroy() { | ||
| this.cache = null; | ||
| this.cacheQueue = null; | ||
| } | ||
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| /** | ||
| * Caches a simple object in memory. If the number of cache entries | ||
| * then exceeds the maxEntries value, then the earliest key in cacheQueue | ||
| * will be removed from the cache. | ||
| * | ||
| * @param {string} key - The cache key | ||
| * @param {*} value - The cache value | ||
| * @return {void} | ||
| */ | ||
| set(key, value) { | ||
| // If this key is not already in the cache, then add it | ||
| // to the cacheQueue. This avoids adding the same key to | ||
| // the cacheQueue multiple times if the cache entry gets updated | ||
| if (!this.inCache(key)) { | ||
| this.cacheQueue.push(key); | ||
| } | ||
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| super.set(key, value); | ||
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| // If the cacheQueue exceeds the maxEntries then remove the first | ||
| // key from the front of the cacheQueue and unset that entry | ||
| // from the cache | ||
| if (this.cacheQueue.length > this.maxEntries) { | ||
| const deleteKey = this.cacheQueue.shift(); | ||
| this.unset(deleteKey); | ||
| } | ||
| } | ||
| } | ||
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| export default BoundedCache; |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,59 @@ | ||
| /* eslint-disable no-unused-expressions */ | ||
| import BoundedCache from '../BoundedCache'; | ||
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| const sandbox = sinon.sandbox.create(); | ||
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| describe('BoundedCache', () => { | ||
| let cache; | ||
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| beforeEach(() => { | ||
| cache = new BoundedCache(2); | ||
| }); | ||
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| afterEach(() => { | ||
| sandbox.verifyAndRestore(); | ||
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| cache = null; | ||
| }); | ||
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| describe('constructor()', () => { | ||
| it('should initialize properties', () => { | ||
| cache = new BoundedCache(); | ||
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| expect(cache.maxEntries).to.be.equal(500); | ||
| expect(cache.cache).to.be.empty; | ||
| expect(cache.cacheQueue.length).to.be.equal(0); | ||
| }); | ||
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| it('should handle maxEntries', () => { | ||
| expect(cache.maxEntries).to.be.equal(2); | ||
| }); | ||
| }); | ||
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| describe('set()', () => { | ||
| it('should add the entry to the cache', () => { | ||
| cache.set('foo', 'bar'); | ||
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| expect(cache.inCache('foo')).to.be.true; | ||
| expect(cache.cacheQueue).to.be.eql(['foo']); | ||
| }); | ||
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| it('should not update the cacheQueue if key already exists', () => { | ||
| cache.set('foo', 'bar'); | ||
| cache.set('foo', 'bar2'); | ||
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| expect(cache.inCache('foo')).to.be.true; | ||
| expect(cache.get('foo')).to.be.equal('bar2'); | ||
| expect(cache.cacheQueue).to.be.eql(['foo']); | ||
| }); | ||
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| it('should remove the earliest added entry when entries exceed maxEntries', () => { | ||
| cache.set('foo', 'bar'); | ||
| cache.set('hello', 'world'); | ||
| cache.set('goodnight', 'moon'); | ||
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| expect(cache.inCache('foo')).to.be.false; | ||
| expect(cache.cacheQueue).to.be.eql(['hello', 'goodnight']); | ||
| }); | ||
| }); | ||
| }); |
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