Add deno.truncate (#805)

1 files changed, 73 insertions, 0 deletions

diff --git a/js/truncate_test.ts b/js/truncate_test.ts
new file mode 100644
index 000000000..4b9cae445
--- /dev/null
+++ b/js/truncate_test.ts
@@ -0,0 +1,73 @@
+// Copyright 2018 the Deno authors. All rights reserved. MIT license.
+import { testPerm, assertEqual } from "./test_util.ts";
+import * as deno from "deno";
+
+function readDataSync(name: string): string {
+  const data = deno.readFileSync(name);
+  const decoder = new TextDecoder("utf-8");
+  const text = decoder.decode(data);
+  return text;
+}
+
+async function readData(name: string): Promise<string> {
+  const data = await deno.readFile(name);
+  const decoder = new TextDecoder("utf-8");
+  const text = decoder.decode(data);
+  return text;
+}
+
+testPerm({ write: true }, function truncateSyncSuccess() {
+  const enc = new TextEncoder();
+  const d = enc.encode("Hello");
+  const filename = deno.makeTempDirSync() + "/test_truncateSync.txt";
+  deno.writeFileSync(filename, d);
+  deno.truncateSync(filename, 20);
+  let data = readDataSync(filename);
+  assertEqual(data.length, 20);
+  deno.truncateSync(filename, 5);
+  data = readDataSync(filename);
+  assertEqual(data.length, 5);
+  deno.truncateSync(filename, -5);
+  data = readDataSync(filename);
+  assertEqual(data.length, 0);
+  deno.removeSync(filename);
+});
+
+testPerm({ write: true }, async function truncateSuccess() {
+  const enc = new TextEncoder();
+  const d = enc.encode("Hello");
+  const filename = deno.makeTempDirSync() + "/test_truncate.txt";
+  await deno.writeFile(filename, d);
+  await deno.truncate(filename, 20);
+  let data = await readData(filename);
+  assertEqual(data.length, 20);
+  await deno.truncate(filename, 5);
+  data = await readData(filename);
+  assertEqual(data.length, 5);
+  await deno.truncate(filename, -5);
+  data = await readData(filename);
+  assertEqual(data.length, 0);
+  await deno.remove(filename);
+});
+
+testPerm({ write: false }, function truncateSyncPerm() {
+  let err;
+  try {
+    deno.mkdirSync("/test_truncateSyncPermission.txt");
+  } catch (e) {
+    err = e;
+  }
+  assertEqual(err.kind, deno.ErrorKind.PermissionDenied);
+  assertEqual(err.name, "PermissionDenied");
+});
+
+testPerm({ write: false }, async function truncatePerm() {
+  let err;
+  try {
+    await deno.mkdir("/test_truncatePermission.txt");
+  } catch (e) {
+    err = e;
+  }
+  assertEqual(err.kind, deno.ErrorKind.PermissionDenied);
+  assertEqual(err.name, "PermissionDenied");
+});