1 files changed, 33 insertions, 0 deletions
diff --git a/cli/js/ops/fs/truncate.ts b/cli/js/ops/fs/truncate.ts
new file mode 100644
index 000000000..578e37aa3
--- /dev/null
+++ b/cli/js/ops/fs/truncate.ts
@@ -0,0 +1,33 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import { sendSync, sendAsync } from "../dispatch_json.ts";
+
+function coerceLen(len?: number): number {
+  if (!len) {
+    return 0;
+  }
+
+  if (len < 0) {
+    return 0;
+  }
+
+  return len;
+}
+
+/** Synchronously truncates or extends the specified file, to reach the
+ * specified `len`.
+ *
+ *       Deno.truncateSync("hello.txt", 10);
+ *
+ * Requires `allow-write` permission. */
+export function truncateSync(path: string, len?: number): void {
+  sendSync("op_truncate", { path, len: coerceLen(len) });
+}
+
+/** Truncates or extends the specified file, to reach the specified `len`.
+ *
+ *       await Deno.truncate("hello.txt", 10);
+ *
+ * Requires `allow-write` permission. */
+export async function truncate(path: string, len?: number): Promise<void> {
+  await sendAsync("op_truncate", { path, len: coerceLen(len) });
+}