feature(fs-copy-file) add mask support introduce in node v10

README.md

@@ -3,7 +3,12 @@ fs-copy-file [![License][LicenseIMGURL]][LicenseURL] [![NPM version][NPMIMGURL]]
 Node.js v8.5.0 [fs.copyFile](https://nodejs.org/dist/latest-v8.x/docs/api/fs.html#fs_fs_copyfile_src_dest_flags_callback) [ponyfill](https://ponyfill.com).
 
 Asynchronously copies `src` to `dest`. By default, `dest` is overwritten if it already exists. No arguments other than a possible exception are given to the callback function.
-`flags` is an optional integer that specifies the behavior of the copy operation. The only supported flag is `COPYFILE_EXCL`, which causes the copy operation to fail if dest already exists.
+
+`flags` is an optional integer that specifies the behavior 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.
 
 ## Install
 

lib/fs-copy-file.js

@@ -4,11 +4,19 @@ const fs = require('fs');
 const _copyFile = require('@cloudcmd/copy-file');
 
 const COPYFILE_EXCL = 1;
+const COPYFILE_FICLONE = 2;
+const COPYFILE_FICLONE_FORCE = 4;
 
 module.exports = fs.copyFile ? fs.copyFile : copyFile;
 
 module.exports.constants = {
-    COPYFILE_EXCL
+    COPYFILE_EXCL,
+    COPYFILE_FICLONE,
+    COPYFILE_FICLONE_FORCE,
+};
+
+const isExcl = (flags) => {
+    return flags & COPYFILE_EXCL;
 };
 
 function copyFile(src, dest, flags, callback) {
@@ -19,7 +27,7 @@ function copyFile(src, dest, flags, callback) {
 
     check(src, dest, flags, callback);
 
-    if (flags !== COPYFILE_EXCL)
+    if (isExcl(flags) !== COPYFILE_EXCL)
         return _copyFile(src, dest, callback);
 
     fs.stat(dest, (error) => {