fs: Fix default params for fs.write(Sync)

Add support for fs.write(fd, buffer, cb) and fs.write(fd, buffer, offset, cb)
as documented at
https://nodejs.org/api/fs.html#fs_fs_write_fd_data_position_encoding_callback
and equivalently for fs.writeSync

Update docs and code comments to reflect the implementation.

PR-URL: https://github.com/nodejs/node/pull/7856
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Brian White <mscdex@mscdex.net>
Reviewed-By: Yorkie Liu <yorkiefixer@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>

1 files changed, 99 insertions, 21 deletions

diff --git a/test/parallel/test-fs-write-buffer.js b/test/parallel/test-fs-write-buffer.js
index b6404a036a..ed77d697b3 100644
--- a/test/parallel/test-fs-write-buffer.js
+++ b/test/parallel/test-fs-write-buffer.js
@@ -2,29 +2,107 @@
 const common = require('../common');
 const assert = require('assert');
 const path = require('path');
-const Buffer = require('buffer').Buffer;
 const fs = require('fs');
-const filename = path.join(common.tmpDir, 'write.txt');
 const expected = Buffer.from('hello');
 
 common.refreshTmpDir();
 
-fs.open(filename, 'w', 0o644, common.mustCall(function(err, fd) {
-  if (err) throw err;
-
-  fs.write(fd,
-           expected,
-           0,
-           expected.length,
-           null,
-           common.mustCall(function(err, written) {
-             if (err) throw err;
-
-             assert.equal(expected.length, written);
-             fs.closeSync(fd);
-
-             var found = fs.readFileSync(filename, 'utf8');
-             assert.deepStrictEqual(expected.toString(), found);
-             fs.unlinkSync(filename);
-           }));
-}));
+// fs.write with all parameters provided:
+{
+  const filename = path.join(common.tmpDir, 'write1.txt');
+  fs.open(filename, 'w', 0o644, common.mustCall(function(err, fd) {
+    assert.ifError(err);
+
+    const cb = common.mustCall(function(err, written) {
+      assert.ifError(err);
+
+      assert.strictEqual(expected.length, written);
+      fs.closeSync(fd);
+
+      var found = fs.readFileSync(filename, 'utf8');
+      assert.deepStrictEqual(expected.toString(), found);
+    });
+
+    fs.write(fd, expected, 0, expected.length, null, cb);
+  }));
+}
+
+// fs.write with a buffer, without the length parameter:
+{
+  const filename = path.join(common.tmpDir, 'write2.txt');
+  fs.open(filename, 'w', 0o644, common.mustCall(function(err, fd) {
+    assert.ifError(err);
+
+    const cb = common.mustCall(function(err, written) {
+      assert.ifError(err);
+
+      assert.strictEqual(2, written);
+      fs.closeSync(fd);
+
+      const found = fs.readFileSync(filename, 'utf8');
+      assert.deepStrictEqual('lo', found);
+    });
+
+    fs.write(fd, Buffer.from('hello'), 3, cb);
+  }));
+}
+
+// fs.write with a buffer, without the offset and length parameters:
+{
+  const filename = path.join(common.tmpDir, 'write3.txt');
+  fs.open(filename, 'w', 0o644, common.mustCall(function(err, fd) {
+    assert.ifError(err);
+
+    const cb = common.mustCall(function(err, written) {
+      assert.ifError(err);
+
+      assert.strictEqual(expected.length, written);
+      fs.closeSync(fd);
+
+      const found = fs.readFileSync(filename, 'utf8');
+      assert.deepStrictEqual(expected.toString(), found);
+    });
+
+    fs.write(fd, expected, cb);
+  }));
+}
+
+// fs.write with the offset passed as undefined followed by the callback:
+{
+  const filename = path.join(common.tmpDir, 'write4.txt');
+  fs.open(filename, 'w', 0o644, common.mustCall(function(err, fd) {
+    assert.ifError(err);
+
+    const cb = common.mustCall(function(err, written) {
+      assert.ifError(err);
+
+      assert.strictEqual(expected.length, written);
+      fs.closeSync(fd);
+
+      const found = fs.readFileSync(filename, 'utf8');
+      assert.deepStrictEqual(expected.toString(), found);
+    });
+
+    fs.write(fd, expected, undefined, cb);
+  }));
+}
+
+// fs.write with offset and length passed as undefined followed by the callback:
+{
+  const filename = path.join(common.tmpDir, 'write5.txt');
+  fs.open(filename, 'w', 0o644, common.mustCall(function(err, fd) {
+    assert.ifError(err);
+
+    const cb = common.mustCall(function(err, written) {
+      assert.ifError(err);
+
+      assert.strictEqual(expected.length, written);
+      fs.closeSync(fd);
+
+      const found = fs.readFileSync(filename, 'utf8');
+      assert.deepStrictEqual(expected.toString(), found);
+    });
+
+    fs.write(fd, expected, undefined, undefined, cb);
+  }));
+}