Turns a Reader, r, into an async iterator.

let f = await Deno.open("/etc/passwd");
for await (const chunk of Deno.iter(f)) {
  console.log(chunk);
}
f.close();

Second argument can be used to tune size of a buffer. Default size of the buffer is 32kB.

let f = await Deno.open("/etc/passwd");
const iter = Deno.iter(f, {
  bufSize: 1024 * 1024
});
for await (const chunk of iter) {
  console.log(chunk);
}
f.close();

Iterator uses an internal buffer of fixed size for efficiency; it returns a view on that buffer on each iteration. It is therefore caller's responsibility to copy contents of the buffer if needed; otherwise the next iteration will overwrite contents of previously returned chunk.