Implement deno.readlink() (#797)

1 files changed, 46 insertions, 0 deletions

diff --git a/js/read_link.ts b/js/read_link.ts
new file mode 100644
index 000000000..6bd613389
--- /dev/null
+++ b/js/read_link.ts
@@ -0,0 +1,46 @@
+// Copyright 2018 the Deno authors. All rights reserved. MIT license.
+import * as fbs from "gen/msg_generated";
+import { flatbuffers } from "flatbuffers";
+import { assert } from "./util";
+import * as dispatch from "./dispatch";
+
+/**
+ * Returns the destination of the named symbolic link synchronously.
+ *
+ *     import { readlinkSync } from "deno";
+ *     const targetPath = readlinkSync("symlink/path");
+ */
+export function readlinkSync(name: string): string {
+  return res(dispatch.sendSync(...req(name)));
+}
+
+/**
+ * Returns the destination of the named symbolic link.
+ *
+ *     import { readlink } from "deno";
+ *     const targetPath = await readlink("symlink/path");
+ */
+export async function readlink(name: string): Promise<string> {
+  return res(await dispatch.sendAsync(...req(name)));
+}
+
+function req(
+  name: string
+): [flatbuffers.Builder, fbs.Any, flatbuffers.Offset] {
+  const builder = new flatbuffers.Builder();
+  const name_ = builder.createString(name);
+  fbs.Readlink.startReadlink(builder);
+  fbs.Readlink.addName(builder, name_);
+  const msg = fbs.Readlink.endReadlink(builder);
+  return [builder, fbs.Any.Readlink, msg];
+}
+
+function res(baseRes: null | fbs.Base): string {
+  assert(baseRes !== null);
+  assert(fbs.Any.ReadlinkRes === baseRes!.msgType());
+  const res = new fbs.ReadlinkRes();
+  assert(baseRes!.msg(res) !== null);
+  const path = res.path();
+  assert(path !== null);
+  return path!;
+}