perf: reduce number of native calls from fetch.body (nodejs#1792)

Author: anonrig

lib/fetch/body.js

@@ -150,22 +150,18 @@ function extractBody (object, keepalive = false) {
         if (typeof value === 'string') {
           bodyLength +=
             prefixLength +
-            Buffer.byteLength(`; name="${escape(normalizeLinefeeds(name))}"`) +
-            Buffer.byteLength(`\r\n\r\n${normalizeLinefeeds(value)}\r\n`)
+            Buffer.byteLength(`; name="${escape(normalizeLinefeeds(name))}"\r\n\r\n${normalizeLinefeeds(value)}\r\n`)
         } else {
           bodyLength +=
             prefixLength +
-            Buffer.byteLength(`; name="${escape(normalizeLinefeeds(name))}"`) +
-            (value.name ? Buffer.byteLength(`; filename="${escape(value.name)}"`) : 0) +
+            Buffer.byteLength(`; name="${escape(normalizeLinefeeds(name))}"` + (value.name ? `; filename="${escape(value.name)}"` : '')) +
             2 + // \r\n
             `Content-Type: ${
               value.type || 'application/octet-stream'
             }\r\n\r\n`.length
 
-          // value is a Blob or File
-          bodyLength += value.size
-
-          bodyLength += 2 // \r\n
+          // value is a Blob or File, and \r\n
+          bodyLength += value.size + 2
         }
       }
 
@@ -393,7 +389,7 @@ function bodyMixinMethods (instance) {
           const { filename, encoding, mimeType } = info
           const chunks = []
 
-          if (encoding.toLowerCase() === 'base64') {
+          if (encoding === 'base64' || encoding.toLowerCase() === 'base64') {
             let base64chunk = ''
 
             value.on('data', (chunk) => {