perf: cache buffer form of CID when created

refs ipfs/js-ipfs#1788

License: MIT
Signed-off-by: Alan Shaw <[email protected]>

Author: Alan Shaw

src/index.js

@@ -122,18 +122,26 @@ class CID {
    * @memberOf CID
    */
   get buffer () {
-    switch (this.version) {
-      case 0:
-        return this.multihash
-      case 1:
-        return Buffer.concat([
+    let buffer = this._buffer
+
+    if (!buffer) {
+      if (this.version === 0) {
+        buffer = this.multihash
+      } else if (this.version === 1) {
+        buffer = Buffer.concat([
           Buffer.from('01', 'hex'),
           multicodec.getCodeVarint(this.codec),
           this.multihash
         ])
-      default:
+      } else {
         throw new Error('unsupported version')
+      }
+
+      // Cache this buffer so it doesn't have to be recreated
+      Object.defineProperty(this, '_buffer', { value: buffer })
     }
+
+    return buffer
   }
 
   /**

test/index.spec.js

@@ -300,4 +300,15 @@ describe('CID', () => {
       })
     })
   })
+
+  describe('buffer reuse', () => {
+    it('should cache CID as buffer', done => {
+      multihashing(Buffer.from(`TEST${Date.now()}`), 'sha2-256', (err, hash) => {
+        if (err) return done(err)
+        const cid = new CID(1, 'dag-pb', hash)
+        expect(cid.buffer).to.equal(cid.buffer)
+        done()
+      })
+    })
+  })
 })