feat(size): add optional callback

README.md

@@ -53,4 +53,7 @@ Transform stream that operates in object mode and returns a single `{
 size: 1000 }` object where the size is an integer representing the total
 size in bytes of the stream.
 
-`new SizeStream()`
+`new SizeStream()`
+
+If passed a callback `new SizeStream(cb)` it will just act as a
+PassThrough stream and call the callback when it's done.

package.json

@@ -1,6 +1,6 @@
 {
   "name": "common-streams",
-  "version": "1.0.0",
+  "version": "1.0.1",
   "description": "",
   "main": "./lib/index.js",
   "directories": {
@@ -56,4 +56,4 @@
       "path": "cz-conventional-changelog"
     }
   }
-}
+}

src/SizeStream.js

@@ -1,20 +1,33 @@
 import { Transform } from 'stream'
 
 export default class SizeStream extends Transform {
-  constructor() {
+  constructor(cb) {
     super({ objectMode: true })
     this.streamSize = 0
+    this.cb = cb
   }
 
   _transform(chunk, encoding, cb) {
+    if (this.cb) return this._transformCb(chunk, encoding, cb)
     // Update hash sum objects
     this.streamSize = this.streamSize + chunk.length
     cb()
   }
 
   _flush(cb) {
+    if (this.cb) return this._flushCb(cb)
     const size = this.streamSize
     this.push({ size })
     cb(null)
   }
+
+  _transformCb(chunk, encoding, cb) {
+    this.streamSize = this.streamSize + chunk.length
+    cb(null, chunk)
+  }
+  _flushCb(cb) {
+    const size = this.streamSize
+    this.cb(size)
+    cb(null)
+  }
 }

test/index.test.js

@@ -52,3 +52,20 @@ test('kitchen sink', (t) => {
   }))
   rs.pipe(ws)
 })
+
+test('size stream through', (t) => {
+  const rs = getReadStream()
+  const ws = getWriteStream()
+
+  t.plan(2)
+
+  const sizeStream = new SizeStream((size) => {
+    t.equal(size, 2447774)
+  })
+
+  ws.on('finish', () => {
+    t.ok(true)
+  })
+
+  rs.pipe(sizeStream).pipe(ws)
+})