Add buffer size argument to copy (#4907)

1 files changed, 9 insertions, 2 deletions

diff --git a/cli/js/io.ts b/cli/js/io.ts
index 50ea1216a..833d23874 100644
--- a/cli/js/io.ts
+++ b/cli/js/io.ts
@@ -70,9 +70,16 @@ export interface ReadWriteCloser extends Reader, Writer, Closer {}
 // https://golang.org/pkg/io/#ReadWriteSeeker
 export interface ReadWriteSeeker extends Reader, Writer, Seeker {}
 
-export async function copy(src: Reader, dst: Writer): Promise<number> {
+export async function copy(
+  src: Reader,
+  dst: Writer,
+  options?: {
+    bufSize?: number;
+  }
+): Promise<number> {
   let n = 0;
-  const b = new Uint8Array(DEFAULT_BUFFER_SIZE);
+  const bufSize = options?.bufSize ?? DEFAULT_BUFFER_SIZE;
+  const b = new Uint8Array(bufSize);
   let gotEOF = false;
   while (gotEOF === false) {
     const result = await src.read(b);