1 files changed, 34 insertions, 0 deletions
diff --git a/cli/js/truncate.ts b/cli/js/truncate.ts
new file mode 100644
index 000000000..5ce7b5158
--- /dev/null
+++ b/cli/js/truncate.ts
@@ -0,0 +1,34 @@
+// Copyright 2018-2019 the Deno authors. All rights reserved. MIT license.
+import { sendSync, sendAsync } from "./dispatch_json.ts";
+import * as dispatch from "./dispatch.ts";
+
+function coerceLen(len?: number): number {
+  if (!len) {
+    return 0;
+  }
+
+  if (len < 0) {
+    return 0;
+  }
+
+  return len;
+}
+
+/** Truncates or extends the specified file synchronously, updating the size of
+ * this file to become size.
+ *
+ *       Deno.truncateSync("hello.txt", 10);
+ */
+export function truncateSync(name: string, len?: number): void {
+  sendSync(dispatch.OP_TRUNCATE, { name, len: coerceLen(len) });
+}
+
+/**
+ * Truncates or extends the specified file, updating the size of this file to
+ * become size.
+ *
+ *       await Deno.truncate("hello.txt", 10);
+ */
+export async function truncate(name: string, len?: number): Promise<void> {
+  await sendAsync(dispatch.OP_TRUNCATE, { name, len: coerceLen(len) });
+}