Add chmod/chmodSync on unix (and fix Cargo.toml) (#1088)

Initial implementation by Srijan Reddy (@srijanreddy98, #672).

js/chmod.ts

@@ -0,0 +1,36 @@
+// Copyright 2018 the Deno authors. All rights reserved. MIT license.
+import * as msg from "gen/msg_generated";
+import * as flatbuffers from "./flatbuffers";
+import * as dispatch from "./dispatch";
+
+/** Changes the permission of a specific file/directory of specified path
+ * synchronously.
+ *
+ *       import { chmodSync } from "deno";
+ *       chmodSync("/path/to/file", 0o666);
+ */
+export function chmodSync(path: string, mode: number): void {
+  dispatch.sendSync(...req(path, mode));
+}
+
+/** Changes the permission of a specific file/directory of specified path.
+ *
+ *       import { chmod } from "deno";
+ *       await chmod("/path/to/file", 0o666);
+ */
+export async function chmod(path: string, mode: number): Promise<void> {
+  await dispatch.sendAsync(...req(path, mode));
+}
+
+function req(
+  path: string,
+  mode: number
+): [flatbuffers.Builder, msg.Any, flatbuffers.Offset] {
+  const builder = flatbuffers.createBuilder();
+  const path_ = builder.createString(path);
+  msg.Chmod.startChmod(builder);
+  msg.Chmod.addPath(builder, path_);
+  msg.Chmod.addMode(builder, mode);
+  const inner = msg.Chmod.endChmod(builder);
+  return [builder, msg.Any.Chmod, inner];
+}