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fs: add writev() promises version

#25925 added fs.writev()
and fs.writevSync(), but did not include a Promises based
equivalent. This commit adds the missing method.

Refs: #25925
PR-URL: #29186
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
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cjihrig authored and targos committed Aug 17, 2019
1 parent 4356836 commit 81f3eb5bb1899fbc0f0418440b0ba0cc1a70ae6a
Showing with 108 additions and 0 deletions.
  1. +26 −0 doc/api/fs.md
  2. +17 −0 lib/internal/fs/promises.js
  3. +14 −0 lib/internal/fs/utils.js
  4. +51 −0 test/parallel/test-fs-writev-promises.js
@@ -4212,6 +4212,32 @@ If one or more `filehandle.write()` calls are made on a file handle and then a
current position till the end of the file. It doesn't always write from the
beginning of the file.

#### filehandle.writev(buffers[, position])
<!-- YAML
added: REPLACEME
-->

* `buffers` {ArrayBufferView[]}
* `position` {integer}
* Returns: {Promise}

Write an array of `ArrayBufferView`s to the file.

The `Promise` is resolved with an object containing a `bytesWritten` property
identifying the number of bytes written, and a `buffers` property containing
a reference to the `buffers` input.

`position` is the offset from the beginning of the file where this data
should be written. If `typeof position !== 'number'`, the data will be written
at the current position.

It is unsafe to call `writev()` multiple times on the same file without waiting
for the previous operation to complete.

On Linux, positional writes don't work when the file is opened in append mode.
The kernel ignores the position argument and always appends the data to
the end of the file.

### fsPromises.access(path[, mode])
<!-- YAML
added: v10.0.0
@@ -29,6 +29,7 @@ const {
stringToFlags,
stringToSymlinkType,
toUnixTimestamp,
validateBufferArray,
validateOffsetLengthRead,
validateOffsetLengthWrite,
warnOnNonPortableTemplate
@@ -104,6 +105,10 @@ class FileHandle {
return write(this, buffer, offset, length, position);
}

writev(buffers, position) {
return writev(this, buffers, position);
}

writeFile(data, options) {
return writeFile(this, data, options);
}
@@ -255,6 +260,18 @@ async function write(handle, buffer, offset, length, position) {
return { bytesWritten, buffer };
}

async function writev(handle, buffers, position) {
validateFileHandle(handle);
validateBufferArray(buffers);

if (typeof position !== 'number')
position = null;

const bytesWritten = (await binding.writeBuffers(handle.fd, buffers, position,
kUsePromises)) || 0;
return { bytesWritten, buffers };
}

async function rename(oldPath, newPath) {
oldPath = getValidatedPath(oldPath, 'oldPath');
newPath = getValidatedPath(newPath, 'newPath');
@@ -15,6 +15,7 @@ const {
hideStackFrames
} = require('internal/errors');
const {
isArrayBufferView,
isUint8Array,
isDate
} = require('internal/util/types');
@@ -439,6 +440,18 @@ const getValidatedPath = hideStackFrames((fileURLOrPath, propName = 'path') => {
return path;
});

const validateBufferArray = hideStackFrames((buffers, propName = 'buffers') => {
if (!Array.isArray(buffers))
throw new ERR_INVALID_ARG_TYPE(propName, 'ArrayBufferView[]', buffers);

for (let i = 0; i < buffers.length; i++) {
if (!isArrayBufferView(buffers[i]))
throw new ERR_INVALID_ARG_TYPE(propName, 'ArrayBufferView[]', buffers);
}

return buffers;
});

let nonPortableTemplateWarn = true;

function warnOnNonPortableTemplate(template) {
@@ -466,6 +479,7 @@ module.exports = {
stringToSymlinkType,
Stats,
toUnixTimestamp,
validateBufferArray,
validateOffsetLengthRead,
validateOffsetLengthWrite,
validatePath,
@@ -0,0 +1,51 @@
'use strict';

require('../common');
const assert = require('assert');
const path = require('path');
const fs = require('fs').promises;
const tmpdir = require('../common/tmpdir');
const expected = 'ümlaut. Лорем 運務ホソモ指及 आपको करने विकास 紙読決多密所 أضف';
let cnt = 0;

function getFileName() {
return path.join(tmpdir.path, `writev_promises_${++cnt}.txt`);
}

tmpdir.refresh();

(async () => {
{
const filename = getFileName();
const handle = await fs.open(filename, 'w');
const buffer = Buffer.from(expected);
const bufferArr = [buffer, buffer];
const expectedLength = bufferArr.length * buffer.byteLength;
let { bytesWritten, buffers } = await handle.writev([Buffer.from('')],
null);
assert.deepStrictEqual(bytesWritten, 0);
assert.deepStrictEqual(buffers, [Buffer.from('')]);
({ bytesWritten, buffers } = await handle.writev(bufferArr, null));
assert.deepStrictEqual(bytesWritten, expectedLength);
assert.deepStrictEqual(buffers, bufferArr);
assert(Buffer.concat(bufferArr).equals(await fs.readFile(filename)));
handle.close();
}

// fs.promises.writev() with an array of buffers without position.
{
const filename = getFileName();
const handle = await fs.open(filename, 'w');
const buffer = Buffer.from(expected);
const bufferArr = [buffer, buffer, buffer];
const expectedLength = bufferArr.length * buffer.byteLength;
let { bytesWritten, buffers } = await handle.writev([Buffer.from('')]);
assert.deepStrictEqual(bytesWritten, 0);
assert.deepStrictEqual(buffers, [Buffer.from('')]);
({ bytesWritten, buffers } = await handle.writev(bufferArr));
assert.deepStrictEqual(bytesWritten, expectedLength);
assert.deepStrictEqual(buffers, bufferArr);
assert(Buffer.concat(bufferArr).equals(await fs.readFile(filename)));
handle.close();
}
})();

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