fs: make parameters optional for readSync

lholmquist · targos · commit 991aca329d13 · 2020-04-11T10:05:42.000+02:00
This makes the offset, length and position parameters optional by passing in an options object. PR-URL: #32460 Reviewed-By: Anna Henningsen <anna@addaleax.net>
diff --git a/doc/api/fs.md b/doc/api/fs.md
@@ -3080,6 +3080,32 @@ Returns the number of `bytesRead`.
 For detailed information, see the documentation of the asynchronous version of
 this API: [`fs.read()`][].
 
+## `fs.readSync(fd, buffer, [options])`
+<!-- YAML
+added: REPLACEME
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/32460
+    description: Options object can be passed in
+                 to make offset, length and position optional
+-->
+
+* `fd` {integer}
+* `buffer` {Buffer|TypedArray|DataView}
+* `options` {Object}
+  * `offset` {integer} **Default:** `0`
+  * `length` {integer} **Default:** `buffer.length`
+  * `position` {integer} **Default:** `null`
+* Returns: {number}
+
+Returns the number of `bytesRead`.
+
+Similar to the above `fs.readSync` function, this version takes an optional `options` object.
+If no `options` object is specified, it will default with the above values.
+
+For detailed information, see the documentation of the asynchronous version of
+this API: [`fs.read()`][].
+
 ## `fs.readv(fd, buffers[, position], callback)`
 <!-- YAML
 added: REPLACEME
diff --git a/lib/fs.js b/lib/fs.js
@@ -534,8 +534,20 @@ function read(fd, buffer, offset, length, position, callback) {
 ObjectDefineProperty(read, internalUtil.customPromisifyArgs,
                      { value: ['bytesRead', 'buffer'], enumerable: false });
 
+// usage:
+// fs.readSync(fd, buffer, offset, length, position);
+// OR
+// fs.readSync(fd, buffer, {}) or fs.readSync(fd, buffer)
 function readSync(fd, buffer, offset, length, position) {
   validateInt32(fd, 'fd', 0);
+
+  if (arguments.length <= 3) {
+    // Assume fs.read(fd, buffer, options)
+    const options = offset || {};
+
+    ({ offset = 0, length = buffer.length, position } = options);
+  }
+
   validateBuffer(buffer);
 
   if (offset == null) {
diff --git a/test/parallel/test-fs-readSync-optional-params.js b/test/parallel/test-fs-readSync-optional-params.js
@@ -0,0 +1,27 @@
+'use strict';
+
+require('../common');
+const fixtures = require('../common/fixtures');
+const fs = require('fs');
+const assert = require('assert');
+const filepath = fixtures.path('x.txt');
+const fd = fs.openSync(filepath, 'r');
+
+const expected = Buffer.from('xyz\n');
+
+function runTest(defaultBuffer, options) {
+  const result = fs.readSync(fd, defaultBuffer, options);
+  assert.strictEqual(result, expected.length);
+  assert.deepStrictEqual(defaultBuffer, expected);
+}
+
+// Test passing in an empty options object
+runTest(Buffer.allocUnsafe(expected.length), { position: 0 });
+
+// Test not passing in any options object
+runTest(Buffer.allocUnsafe(expected.length));
+
+// Test passing in options
+runTest(Buffer.allocUnsafe(expected.length), { offset: 0,
+                                               length: expected.length,
+                                               position: 0 });
