feat(runtime): add truncate and truncateSync methods to Deno.File

cli/dts/lib.deno.ns.d.ts

@@ -781,6 +781,8 @@ declare namespace Deno {
  constructor(rid: number);
  write(p: Uint8Array): Promise<number>;
  writeSync(p: Uint8Array): number;
+ truncate(len?: number): void;
+ truncateSync(len?: number): Promise<void>;
  read(p: Uint8Array): Promise<number | null>;
  readSync(p: Uint8Array): number | null;
  seek(offset: number, whence: SeekMode): Promise<number>;

cli/tests/unit/file_test.ts

@@ -103,3 +103,47 @@ unitTest(function fileUsingNumberFileName(): void {
 unitTest(function fileUsingEmptyStringFileName(): void {
  testSecondArgument("", "");
 });
+
+unitTest(
+ { perms: { read: true, write: true } },
+ function fileTruncateSyncSuccess(): void {
+ const filename = Deno.makeTempDirSync() + "/test_fileTruncateSync.txt";
+ const file = Deno.openSync(filename, {
+ create: true,
+ read: true,
+ write: true,
+ });
+
+ file.truncateSync(20);
+ assertEquals(Deno.readFileSync(filename).byteLength, 20);
+ file.truncateSync(5);
+ assertEquals(Deno.readFileSync(filename).byteLength, 5);
+ file.truncateSync(-5);
+ assertEquals(Deno.readFileSync(filename).byteLength, 0);
+
+ file.close();
+ Deno.removeSync(filename);
+ },
+);
+
+unitTest(
+ { perms: { read: true, write: true } },
+ async function fileTruncateSuccess(): Promise<void> {
+ const filename = Deno.makeTempDirSync() + "/test_fileTruncate.txt";
+ const file = await Deno.open(filename, {
+ create: true,
+ read: true,
+ write: true,
+ });
+
+ await file.truncate(20);
+ assertEquals((await Deno.readFile(filename)).byteLength, 20);
+ await file.truncate(5);
+ assertEquals((await Deno.readFile(filename)).byteLength, 5);
+ await file.truncate(-5);
+ assertEquals((await Deno.readFile(filename)).byteLength, 0);
+
+ file.close();
+ await Deno.remove(filename);
+ },
+);

runtime/js/30_files.js → runtime/js/40_files.js

@@ -4,6 +4,7 @@
 ((window) => {
  const core = window.Deno.core;
  const { read, readSync, write, writeSync } = window.__bootstrap.io;
+ const { ftruncate, ftruncateSync } = window.__bootstrap.fs;
  const { pathFromURL } = window.__bootstrap.util;
 
  function seekSync(
@@ -87,6 +88,14 @@
  return writeSync(this.rid, p);
  }
 
+ truncate(len) {
+ return ftruncate(this.rid, len);
+ }
+
+ truncateSync(len) {
+ return ftruncateSync(this.rid, len);
+ }
+
  read(p) {
  return read(this.rid, p);
  }