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fs: expose copy-on-write flags for fs.copyFile()
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This commit exposes the UV_FS_COPYFILE_FICLONE and
UV_FS_COPYFILE_FICLONE_FORCE flags added in libuv 1.20.0.

Fixes: #19152
PR-URL: #19759
Fixes: #19152
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
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cjihrig committed Apr 6, 2018
1 parent 6179467 commit a16d88d
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Showing 4 changed files with 107 additions and 9 deletions.
70 changes: 64 additions & 6 deletions doc/api/fs.md
Original file line number Diff line number Diff line change
Expand Up @@ -1175,8 +1175,18 @@ operation. If an error occurs after the destination file has been opened for
writing, Node.js will attempt to remove the destination.

`flags` is an optional integer that specifies the behavior
of the copy operation. The only supported flag is `fs.constants.COPYFILE_EXCL`,
which causes the copy operation to fail if `dest` already exists.
of the copy operation. It is possible to create a mask consisting of the bitwise
OR of two or more values (e.g.
`fs.constants.COPYFILE_EXCL | fs.constants.COPYFILE_FICLONE`).

* `fs.constants.COPYFILE_EXCL` - The copy operation will fail if `dest` already
exists.
* `fs.constants.COPYFILE_FICLONE` - The copy operation will attempt to create a
copy-on-write reflink. If the platform does not support copy-on-write, then a
fallback copy mechanism is used.
* `fs.constants.COPYFILE_FICLONE_FORCE` - The copy operation will attempt to
create a copy-on-write reflink. If the platform does not support copy-on-write,
then the operation will fail.

Example:

Expand Down Expand Up @@ -1216,8 +1226,18 @@ atomicity of the copy operation. If an error occurs after the destination file
has been opened for writing, Node.js will attempt to remove the destination.

`flags` is an optional integer that specifies the behavior
of the copy operation. The only supported flag is `fs.constants.COPYFILE_EXCL`,
which causes the copy operation to fail if `dest` already exists.
of the copy operation. It is possible to create a mask consisting of the bitwise
OR of two or more values (e.g.
`fs.constants.COPYFILE_EXCL | fs.constants.COPYFILE_FICLONE`).

* `fs.constants.COPYFILE_EXCL` - The copy operation will fail if `dest` already
exists.
* `fs.constants.COPYFILE_FICLONE` - The copy operation will attempt to create a
copy-on-write reflink. If the platform does not support copy-on-write, then a
fallback copy mechanism is used.
* `fs.constants.COPYFILE_FICLONE_FORCE` - The copy operation will attempt to
create a copy-on-write reflink. If the platform does not support copy-on-write,
then the operation will fail.

Example:

Expand Down Expand Up @@ -3814,8 +3834,18 @@ error occurs after the destination file has been opened for writing, Node.js
will attempt to remove the destination.

`flags` is an optional integer that specifies the behavior
of the copy operation. The only supported flag is `fs.constants.COPYFILE_EXCL`,
which causes the copy operation to fail if `dest` already exists.
of the copy operation. It is possible to create a mask consisting of the bitwise
OR of two or more values (e.g.
`fs.constants.COPYFILE_EXCL | fs.constants.COPYFILE_FICLONE`).

* `fs.constants.COPYFILE_EXCL` - The copy operation will fail if `dest` already
exists.
* `fs.constants.COPYFILE_FICLONE` - The copy operation will attempt to create a
copy-on-write reflink. If the platform does not support copy-on-write, then a
fallback copy mechanism is used.
* `fs.constants.COPYFILE_FICLONE_FORCE` - The copy operation will attempt to
create a copy-on-write reflink. If the platform does not support copy-on-write,
then the operation will fail.

Example:

Expand Down Expand Up @@ -4449,6 +4479,34 @@ The following constants are meant for use with [`fs.access()`][].
</tr>
</table>

### File Copy Constants

The following constants are meant for use with [`fs.copyFile()`][].

<table>
<tr>
<th>Constant</th>
<th>Description</th>
</tr>
<tr>
<td><code>COPYFILE_EXCL</code></td>
<td>If present, the copy operation will fail with an error if the
destination path already exists.</td>
</tr>
<tr>
<td><code>COPYFILE_FICLONE</code></td>
<td>If present, the copy operation will attempt to create a
copy-on-write reflink. If the underlying platform does not support
copy-on-write, then a fallback copy mechanism is used.</td>
</tr>
<tr>
<td><code>COPYFILE_FICLONE_FORCE</code></td>
<td>If present, the copy operation will attempt to create a
copy-on-write reflink. If the underlying platform does not support
copy-on-write, then the operation will fail with an error.</td>
</tr>
</table>

### File Open Constants

The following constants are meant for use with `fs.open()`.
Expand Down
10 changes: 9 additions & 1 deletion lib/fs.js
Original file line number Diff line number Diff line change
Expand Up @@ -1916,7 +1916,15 @@ fs.mkdtempSync = function(prefix, options) {

// Define copyFile() flags.
Object.defineProperties(fs.constants, {
COPYFILE_EXCL: { enumerable: true, value: constants.UV_FS_COPYFILE_EXCL }
COPYFILE_EXCL: { enumerable: true, value: constants.UV_FS_COPYFILE_EXCL },
COPYFILE_FICLONE: {
enumerable: true,
value: constants.UV_FS_COPYFILE_FICLONE
},
COPYFILE_FICLONE_FORCE: {
enumerable: true,
value: constants.UV_FS_COPYFILE_FICLONE_FORCE
}
});


Expand Down
2 changes: 2 additions & 0 deletions src/node_constants.cc
Original file line number Diff line number Diff line change
Expand Up @@ -1314,6 +1314,8 @@ void DefineConstants(v8::Isolate* isolate, Local<Object> target) {
// Define libuv constants.
NODE_DEFINE_CONSTANT(os_constants, UV_UDP_REUSEADDR);
NODE_DEFINE_CONSTANT(fs_constants, UV_FS_COPYFILE_EXCL);
NODE_DEFINE_CONSTANT(fs_constants, UV_FS_COPYFILE_FICLONE);
NODE_DEFINE_CONSTANT(fs_constants, UV_FS_COPYFILE_FICLONE_FORCE);

os_constants->Set(OneByteString(isolate, "dlopen"), dlopen_constants);
os_constants->Set(OneByteString(isolate, "errno"), err_constants);
Expand Down
34 changes: 32 additions & 2 deletions test/parallel/test-fs-copyfile.js
Original file line number Diff line number Diff line change
Expand Up @@ -8,7 +8,14 @@ const uv = process.binding('uv');
const path = require('path');
const src = fixtures.path('a.js');
const dest = path.join(tmpdir.path, 'copyfile.out');
const { COPYFILE_EXCL, UV_FS_COPYFILE_EXCL } = fs.constants;
const {
COPYFILE_EXCL,
COPYFILE_FICLONE,
COPYFILE_FICLONE_FORCE,
UV_FS_COPYFILE_EXCL,
UV_FS_COPYFILE_FICLONE,
UV_FS_COPYFILE_FICLONE_FORCE
} = fs.constants;

function verify(src, dest) {
const srcData = fs.readFileSync(src, 'utf8');
Expand All @@ -25,8 +32,14 @@ tmpdir.refresh();

// Verify that flags are defined.
assert.strictEqual(typeof COPYFILE_EXCL, 'number');
assert.strictEqual(typeof COPYFILE_FICLONE, 'number');
assert.strictEqual(typeof COPYFILE_FICLONE_FORCE, 'number');
assert.strictEqual(typeof UV_FS_COPYFILE_EXCL, 'number');
assert.strictEqual(typeof UV_FS_COPYFILE_FICLONE, 'number');
assert.strictEqual(typeof UV_FS_COPYFILE_FICLONE_FORCE, 'number');
assert.strictEqual(COPYFILE_EXCL, UV_FS_COPYFILE_EXCL);
assert.strictEqual(COPYFILE_FICLONE, UV_FS_COPYFILE_FICLONE);
assert.strictEqual(COPYFILE_FICLONE_FORCE, UV_FS_COPYFILE_FICLONE_FORCE);

// Verify that files are overwritten when no flags are provided.
fs.writeFileSync(dest, '', 'utf8');
Expand All @@ -38,9 +51,26 @@ verify(src, dest);
fs.copyFileSync(src, dest, 0);
verify(src, dest);

// Verify that UV_FS_COPYFILE_FICLONE can be used.
fs.unlinkSync(dest);
fs.copyFileSync(src, dest, UV_FS_COPYFILE_FICLONE);
verify(src, dest);

// Verify that COPYFILE_FICLONE_FORCE can be used.
try {
fs.unlinkSync(dest);
fs.copyFileSync(src, dest, COPYFILE_FICLONE_FORCE);
verify(src, dest);
} catch (err) {
assert.strictEqual(err.syscall, 'copyfile');
assert(err.code === 'ENOTSUP' || err.code === 'ENOTTY' ||
err.code === 'ENOSYS');
assert.strictEqual(err.path, src);
assert.strictEqual(err.dest, dest);
}

// Copies asynchronously.
fs.unlinkSync(dest);
tmpdir.refresh(); // Don't use unlinkSync() since the last test may fail.
fs.copyFile(src, dest, common.mustCall((err) => {
assert.ifError(err);
verify(src, dest);
Expand Down

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