Deno Roadmap

deno.readFileSync(filename: string): ArrayBuffer;
deno.writeFileSync(filename: string, data: Uint8Array, perm: number): void;

setTimeout(cb: TimerCallback, delay: number, ...args: any[]): number;
setInterval(cb: TimerCallbac, duration: number, ...args: any[]): number;
clearTimeout(timerId: number);
clearInterval(timerId: number);

declare var console: {
  log(...args: any[]): void;
  error(...args: any[]): void;
  assert(assertion: boolean, ...msg: any[]): void;
}

URL(url: string, base?: string): URL;

declare var TextEncoder: {
  new (utfLabel?: string, options?: TextEncoderOptions): TextEncoder;
  (utfLabel?: string, options?: TextEncoderOptions): TextEncoder;
  encoding: string;
};

declare var TextDecoder: {
  new (label?: string, options?: TextDecoderOptions): TextDecoder;
  (label?: string, options?: TextDecoderOptions): TextDecoder;
  encoding: string;
};

fetch(input?: Request | string, init?: RequestInit): Promise<Response>;

// The bytes read during an I/O call and a boolean indicating EOF.
interface ReadResult {
  nread: number;
  eof: boolean;
}

// Reader is the interface that wraps the basic read() method.
// https://golang.org/pkg/io/#Reader
interface Reader {
  // read() reads up to p.byteLength bytes into p. It returns the number of bytes
  // read (0 <= n <= p.byteLength) and any error encountered. Even if read()
  // returns n < p.byteLength, it may use all of p as scratch space during the
  // call. If some data is available but not p.byteLength bytes, read()
  // conventionally returns what is available instead of waiting for more.
  //
  // When read() encounters an error or end-of-file condition after successfully
  // reading n > 0 bytes, it returns the number of bytes read. It may return the
  // (non-nil) error from the same call or return the error (and n == 0) from a
  // subsequent call. An instance of this general case is that a Reader
  // returning a non-zero number of bytes at the end of the input stream may
  // return either err == EOF or err == nil. The next read() should return 0, EOF.
  //
  // Callers should always process the n > 0 bytes returned before considering
  // the error err. Doing so correctly handles I/O errors that happen after
  // reading some bytes and also both of the allowed EOF behaviors.
  //
  // Implementations of read() are discouraged from returning a zero byte count
  // with a nil error, except when p.byteLength == 0. Callers should treat a
  // return of 0 and nil as indicating that nothing happened; in particular it
  // does not indicate EOF.
  //
  // Implementations must not retain p.
  async read(p: ArrayBufferView): Promise<ReadResult>;
}

// Writer is the interface that wraps the basic write() method.
// https://golang.org/pkg/io/#Writer
interface Writer {
  // write() writes p.byteLength bytes from p to the underlying data stream. It
  // returns the number of bytes written from p (0 <= n <= p.byteLength) and any
  // error encountered that caused the write to stop early. write() must return a
  // non-nil error if it returns n < p.byteLength. write() must not modify the
  // slice data, even temporarily.
  //
  // Implementations must not retain p.
  async write(p: ArrayBufferView): Promise<number>;
}

// https://golang.org/pkg/io/#Closer
interface Closer {
  // The behavior of Close after the first call is undefined. Specific
  // implementations may document their own behavior.
  close(): void;
}

// https://golang.org/pkg/io/#Seeker
interface Seeker {
  // Seek sets the offset for the next read() or write() to offset, interpreted
  // according to whence: SeekStart means relative to the start of the file,
  // SeekCurrent means relative to the current offset, and SeekEnd means
  // relative to the end. Seek returns the new offset relative to the start of
  // the file and an error, if any.
  //
  // Seeking to an offset before the start of the file is an error. Seeking to
  // any positive offset is legal, but the behavior of subsequent I/O operations
  // on the underlying object is implementation-dependent.
  async seek(offset: number, whence: number): Promise<void>;
}

// https://golang.org/pkg/io/#ReadCloser
interface ReaderCloser extends Reader, Closer { }

// https://golang.org/pkg/io/#WriteCloser
interface WriteCloser extends Writer, Closer { }

// https://golang.org/pkg/io/#ReadSeeker
interface ReadSeeker extends Reader, Seeker { }

// https://golang.org/pkg/io/#WriteSeeker
interface WriteSeeker extends Writer, Seeker { }

// https://golang.org/pkg/io/#ReadWriteCloser
interface ReadWriteCloser extends Reader, Writer, Closer { }

// https://golang.org/pkg/io/#ReadWriteSeeker
interface ReadWriteSeeker extends Reader, Writer, Seeker { }

// copy() copies from src to dst until either EOF is reached on src or an error
// occurs. It returns the number of bytes copied and the first error encountered
// while copying, if any.
//
// Because copy() is defined to read from src until EOF, it does not treat an EOF
// from read() as an error to be reported.
//
// https://golang.org/pkg/io/#Copy
async function copy(dst: Writer, src: Reader): Promise<number> {
  let n = 0;
  const b = new ArrayBufferView(1024);
  let got_eof = false;
  while (got_eof === false) {
     let result = await src.read(b);
     if (result.eof) got_eof = true;
     n += await dst.write(b.subarray(0, result.nread));
  }
  return n;
}

// MultiWriter creates a writer that duplicates its writes to all the provided
// writers, similar to the Unix tee(1) command.
//
// Each write is written to each listed writer, one at a time. If a listed
// writer returns an error, that overall write operation stops and returns the
// error; it does not continue down the list.
//
// https://golang.org/pkg/io/#MultiWriter
function multiWriter(writers: ...Writer): Writer {
  return {
    write: async (p: ArrayBufferView) => Promise<number> {
      let n;
      let nwritten = await Promise.all(writers.map((w) => w.write(p)));
      return nwritten[0];
      // TODO unsure of proper semantics for return value..
   }
  };
}

function readerIterator(r: deno.Reader): AsyncIterator<ArrayBufferView>;
// Example
for await (let buf of readerIterator(socket)) {
  console.log(`read ${buf.byteLength} from socket`);
}