perf: update MultiplyStream to accept ReadableWritablePair

The `MultiplyStream` class and its associated tests have been updated to accept a `ReadableWritablePair` object instead of a direct `WritableStream`. This modification allows for more flexibility and aligns with common patterns in readable and writable stream manipulations. The change entails adjusting both the constructor's input type and the way writers are instantiated within the `MultiplyStream` class. Consequently, this enhances the class's usability by supporting scenarios that may involve additional stream-related features or requirements encapsulated within a `ReadableWritablePair`. The test updates demonstrate this new capability by adjusting the input format accordingly, ensuring continued compatibility and functionality.

src/multiply-stream.spec.ts

@@ -15,12 +15,16 @@ test("", async () => {
     },
   }).pipeThrough(
     new MultiplyStream(
-      new WritableStream({
-        write: (chunk) => obj1.call(chunk),
-      }),
-      new WritableStream({
-        write: (chunk) => obj1.call(chunk),
-      }),
+      {
+        writable: new WritableStream({
+          write: (chunk) => obj1.call(chunk),
+        }),
+      },
+      {
+        writable: new WritableStream({
+          write: (chunk) => obj1.call(chunk),
+        }),
+      },
     ),
   );
 

src/multiply-stream.ts

@@ -5,10 +5,10 @@ export class MultiplyStream<T> implements ReadableWritablePair<T, T> {
   controller: ReadableStreamDefaultController<T>;
   writable: WritableStream<T>;
 
-  constructor(...writables: WritableStream<T>[]) {
-    const writers = writables.map((writable) => ({
-      writable,
-      writer: writable.getWriter(),
+  constructor(...readableWritablePairs: { writable: WritableStream<T> }[]) {
+    const writers = readableWritablePairs.map((readableWritablePair) => ({
+      writable: readableWritablePair.writable,
+      writer: readableWritablePair.writable.getWriter(),
     }));
     const { readable, controller } = readableStreamWithController<T>();
     this.readable = readable;