Adds basic File I/O and FD table.

Adds deno.stdin, deno.stdout, deno.stderr, deno.open(), deno.write(),
deno.read(), deno.Reader, deno.Writer, deno.copy().

Fixes #721. tests/cat.ts works.

js/files.ts

@@ -0,0 +1,89 @@
+// Copyright 2018 the Deno authors. All rights reserved. MIT license.
+
+import { Reader, Writer, Closer, ReadResult } from "./io";
+import * as dispatch from "./dispatch";
+import * as fbs from "gen/msg_generated";
+import { assert } from "./util";
+import { flatbuffers } from "flatbuffers";
+
+export class File implements Reader, Writer, Closer {
+  constructor(readonly fd: number) {}
+
+  write(p: ArrayBufferView): Promise<number> {
+    return write(this.fd, p);
+  }
+
+  read(p: ArrayBufferView): Promise<ReadResult> {
+    return read(this.fd, p);
+  }
+
+  close(): void {
+    return close(this.fd);
+  }
+}
+
+export const stdin = new File(0);
+export const stdout = new File(1);
+export const stderr = new File(2);
+
+// TODO This is just a placeholder - not final API.
+export type OpenMode = "r" | "w" | "w+" | "x";
+
+export function create(filename: string): Promise<File> {
+  return open(filename, "x");
+}
+
+export async function open(
+  filename: string,
+  mode: OpenMode = "r"
+): Promise<File> {
+  const builder = new flatbuffers.Builder();
+  const filename_ = builder.createString(filename);
+  fbs.Open.startOpen(builder);
+  fbs.Open.addFilename(builder, filename_);
+  const msg = fbs.Open.endOpen(builder);
+  const baseRes = await dispatch.sendAsync(builder, fbs.Any.Open, msg);
+  assert(baseRes != null);
+  assert(fbs.Any.OpenRes === baseRes!.msgType());
+  const res = new fbs.OpenRes();
+  assert(baseRes!.msg(res) != null);
+  const fd = res.fd();
+  return new File(fd);
+}
+
+export async function read(
+  fd: number,
+  p: ArrayBufferView
+): Promise<ReadResult> {
+  const builder = new flatbuffers.Builder();
+  fbs.Read.startRead(builder);
+  fbs.Read.addFd(builder, fd);
+  const msg = fbs.Read.endRead(builder);
+  const baseRes = await dispatch.sendAsync(builder, fbs.Any.Read, msg, p);
+  assert(baseRes != null);
+  assert(fbs.Any.ReadRes === baseRes!.msgType());
+  const res = new fbs.ReadRes();
+  assert(baseRes!.msg(res) != null);
+  return { nread: res.nread(), eof: res.eof() };
+}
+
+export async function write(fd: number, p: ArrayBufferView): Promise<number> {
+  const builder = new flatbuffers.Builder();
+  fbs.Write.startWrite(builder);
+  fbs.Write.addFd(builder, fd);
+  const msg = fbs.Write.endWrite(builder);
+  const baseRes = await dispatch.sendAsync(builder, fbs.Any.Write, msg, p);
+  assert(baseRes != null);
+  assert(fbs.Any.WriteRes === baseRes!.msgType());
+  const res = new fbs.WriteRes();
+  assert(baseRes!.msg(res) != null);
+  return res.nbyte();
+}
+
+export function close(fd: number): void {
+  const builder = new flatbuffers.Builder();
+  fbs.Close.startClose(builder);
+  fbs.Close.addFd(builder, fd);
+  const msg = fbs.Close.endClose(builder);
+  dispatch.sendSync(builder, fbs.Any.Close, msg);
+}