Possible race condition if 2 calls write to the same file

[Soulike]

I think there is a race condition when 2 write() calls write to the same file at almost the same time, like the test case below:

const targetFile = path.join(os.tmpdir(), 'test.txt');

fs.rmSync(targetFile, {force: true});

const content1 = Buffer.alloc(100 * 1024 * 1024); // A will finish writing later than B
const content2 = Buffer.alloc(50 * 1024 * 1024);

crypto.randomFillSync(content1);
crypto.randomFillSync(content2);

process.on('uncaughtException', (e) =>
{
    console.error(e);
});

process.on('beforeExit', () =>
{
    fs.rmSync(targetFile, {force: true});
});

// A
write(targetFile, content1, {overwrite: true}, err =>
{
    if (err)
    {
        console.error(err);
    }
    else
    {
        const targetContent = fs.readFileSync(targetFile);
        assert.ok(targetContent.equals(content1), `The content of targetFile is not content1!`);
    }
});


// B
write(targetFile, content2, {overwrite: true}, err =>
{
    if (err)
    {
        console.error(err);
    }
    else
    {
        const targetContent = fs.readFileSync(targetFile);
        assert.ok(targetContent.equals(content2), `The content of targetFile is not content2!`);
    }
});

And the execution result is:

AssertionError [ERR_ASSERTION]: The content of targetFile is not content2!
...
AssertionError [ERR_ASSERTION]: The content of targetFile is not content1!
...

targetFile may become a corrupted file with content different from either content1 or content2.

I think the bug is caused by the use of stream:

write/index.js

Lines 58 to 61 in f537eb6

	fs.createWriteStream(destpath, opts)
	.on('error', err => reject(err))
	.on('close', resolve)
	.end(ensureNewline(data, opts));

Both A and B can create write streams and write to targetFile at the same time. I think write() should check whether a file is being written before writing to it.