Turns a ReaderSync, r, into an iterator.

import { iterateReaderSync } from "https://deno.land/std@0.199.0/streams/iterate_reader.ts";

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

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

import { iterateReaderSync } from "https://deno.land/std@0.199.0/streams/iterate_reader.ts";

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