Use hash stream instead of crypto.createHash

crypto.createHash is a write stream but not a PassThrough stream!

src/hash-stream.js

@@ -0,0 +1,39 @@
+'use strict';
+
+const crypto = require('crypto'),
+    stream = require('stream'),
+    TransformStream = stream.Transform;
+
+class HashStream extends TransformStream {
+    #hasher;
+    #digest;
+    #size;
+
+    constructor() {
+        super();
+        this.#hasher = crypto.createHash('sha256');
+        this.#digest = null;
+        this.#size = 0;
+    }
+
+    digest() {
+        return this.#digest;
+    }
+
+    size() {
+        return this.#size;
+    }
+
+    _transform(chunk, encoding, callback) {
+        this.#hasher.update(chunk);
+        this.#size += chunk.length;
+        callback(null, chunk);
+    }
+
+    _flush(callback) {
+        this.#digest = this.#hasher.digest('hex');
+        callback(null);
+    }
+}
+
+exports = module.exports = HashStream;