Add "decompressStream" utility

lib/web/fetch/decompress.js

@@ -10,20 +10,7 @@ const { createInflate } = require('./util')
  * @returns {ReadableStream<Uint8Array> | null}
  */
 function decompress (request, response) {
-  const contentEncoding = response.headers.get('content-encoding')
-
-  if (!contentEncoding) {
-    return response.body
-  }
-
-  // https://www.rfc-editor.org/rfc/rfc7231#section-3.1.2.1
-  // "All content-coding values are case-insensitive..."
-  const codings = contentEncoding
-    .toLowerCase()
-    .split(',')
-    .map((coding) => coding.trim())
-
-  if (codings.length === 0) {
+  if (response.body === null) {
     return response.body
   }
 
@@ -41,6 +28,33 @@ function decompress (request, response) {
     return response.body
   }
 
+  return decompressStream(
+    response.body,
+    response.headers.get('content-encoding')
+  )
+}
+
+/**
+ * Decompress the given stream based on the "Content-Encoding" response header.
+ * @param {ReadableStream<Uint8Array>} stream
+ * @param {string | null} contentEncoding The value of the "Content-Encoding" response header.
+ */
+function decompressStream (stream, contentEncoding) {
+  if (!contentEncoding) {
+    return stream
+  }
+
+  // https://www.rfc-editor.org/rfc/rfc7231#section-3.1.2.1
+  // "All content-coding values are case-insensitive..."
+  const codings = contentEncoding
+    .toLowerCase()
+    .split(',')
+    .map((coding) => coding.trim())
+
+  if (codings.length === 0) {
+    return stream
+  }
+
   const decoders = []
 
   for (let i = codings.length - 1; i >= 0; --i) {
@@ -69,12 +83,13 @@ function decompress (request, response) {
   }
 
   if (decoders.length === 0) {
-    return response.body
+    return stream
   }
 
-  return pipeline(response.body, ...decoders, () => {})
+  return pipeline(stream, ...decoders, () => {})
 }
 
 module.exports = {
-  decompress
+  decompress,
+  decompressStream
 }