Implement deno.readFile()

As an example of how to implement ops that have both sync and async
versions.

1 files changed, 50 insertions, 0 deletions

diff --git a/js/read_file.ts b/js/read_file.ts
new file mode 100644
index 000000000..2afea42f1
--- /dev/null
+++ b/js/read_file.ts
@@ -0,0 +1,50 @@
+// 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";
+
+/**
+ * Read the entire contents of a file synchronously.
+ *
+ *     import { readFileSync } from "deno";
+ *     const decoder = new TextDecoder("utf-8");
+ *     const data = readFileSync("hello.txt");
+ *     console.log(decoder.decode(data));
+ */
+export function readFileSync(filename: string): Uint8Array {
+  return res(dispatch.sendSync(...req(filename)));
+}
+
+/**
+ * Read the entire contents of a file.
+ *
+ *     import { readFile } from "deno";
+ *     const decoder = new TextDecoder("utf-8");
+ *     const data = await readFile("hello.txt");
+ *     console.log(decoder.decode(data));
+ */
+export async function readFile(filename: string): Promise<Uint8Array> {
+  return res(await dispatch.sendAsync(...req(filename)));
+}
+
+function req(
+  filename: string
+): [flatbuffers.Builder, fbs.Any, flatbuffers.Offset] {
+  const builder = new flatbuffers.Builder();
+  const filename_ = builder.createString(filename);
+  fbs.ReadFile.startReadFile(builder);
+  fbs.ReadFile.addFilename(builder, filename_);
+  const msg = fbs.ReadFile.endReadFile(builder);
+  return [builder, fbs.Any.ReadFile, msg];
+}
+
+function res(baseRes: null | fbs.Base): Uint8Array {
+  assert(baseRes != null);
+  assert(fbs.Any.ReadFileRes === baseRes!.msgType());
+  const msg = new fbs.ReadFileRes();
+  assert(baseRes!.msg(msg) != null);
+  const dataArray = msg.dataArray();
+  assert(dataArray != null);
+  return new Uint8Array(dataArray!);
+}