Introduce sizeUtils helper

Author: dcsaszar

src/sizeUtils.js

@@ -0,0 +1,8 @@
+const zlib = require('zlib');
+
+export function getCompressedSize(compressionAlgorithm, input) {
+  if (compressionAlgorithm === 'gzip') return zlib.gzipSync(input, {level: 9}).length;
+  if (compressionAlgorithm === 'brotli') return zlib.brotliCompressSync(input).length;
+
+  throw new Error(`Unsupported compression algorithm: ${compressionAlgorithm}.`);
+}