src: refactor require('constants')

The require('constants') module is currently undocumented and mashes
together unrelated constants. This refactors the require('constants')
in favor of distinct os.constants, fs.constants, and crypto.constants
that are specific to the modules for which they are relevant. The
next step is to document those within the specific modules.

PR-URL: #6534
Reviewed-By: Anna Henningsen <[email protected]>
Reviewed-By: Robert Lindstaedt <[email protected]>

 Conflicts:
	doc/api/fs.md

Author: jasnell

doc/api/crypto.md

@@ -315,21 +315,21 @@ checks to be performed. The following constants define the possible values of
 `mode`. It is possible to create a mask consisting of the bitwise OR of two or
 more values.
 
-- `fs.F_OK` - `path` is visible to the calling process. This is useful
+- `fs.constants.F_OK` - `path` is visible to the calling process. This is useful
 for determining if a file exists, but says nothing about `rwx` permissions.
 Default if no `mode` is specified.
-- `fs.R_OK` - `path` can be read by the calling process.
-- `fs.W_OK` - `path` can be written by the calling process.
-- `fs.X_OK` - `path` can be executed by the calling process. This has
-no effect on Windows (will behave like `fs.F_OK`).
+- `fs.constants.R_OK` - `path` can be read by the calling process.
+- `fs.constants.W_OK` - `path` can be written by the calling process.
+- `fs.constants.X_OK` - `path` can be executed by the calling process. This has
+no effect on Windows (will behave like `fs.constants.F_OK`).
 
 The final argument, `callback`, is a callback function that is invoked with
 a possible error argument. If any of the accessibility checks fail, the error
 argument will be populated. The following example checks if the file
 `/etc/passwd` can be read and written by the current process.
 
 ```js
-fs.access('/etc/passwd', fs.R_OK | fs.W_OK, (err) => {
+fs.access('/etc/passwd', fs.constants.R_OK | fs.constants.W_OK, (err) => {
   console.log(err ? 'no access!' : 'can read/write');
 });
 ```
@@ -342,8 +342,8 @@ added: v0.11.15
 * `path` {String | Buffer}
 * `mode` {Integer}
 
-Synchronous version of [`fs.access()`][]. This throws if any accessibility checks
-fail, and does nothing otherwise.
+Synchronous version of [`fs.access()`][]. This throws if any accessibility
+checks fail, and does nothing otherwise.
 
 ## fs.appendFile(file, data[, options], callback)
 <!-- YAML
@@ -460,6 +460,12 @@ added: v0.1.21
 
 Synchronous close(2). Returns `undefined`.
 
+## fs.constants
+
+Returns an object containing commonly used constants for file system
+operations. The specific constants currently defined are described in
+[FS Constants][].
+
 ## fs.createReadStream(path[, options])
 <!-- YAML
 added: v0.1.31
@@ -498,9 +504,9 @@ the file instead of the entire file.  Both `start` and `end` are inclusive and
 start at 0. The `encoding` can be any one of those accepted by [`Buffer`][].
 
 If `fd` is specified, `ReadStream` will ignore the `path` argument and will use
-the specified file descriptor. This means that no `'open'` event will be emitted.
-Note that `fd` should be blocking; non-blocking `fd`s should be passed to
-[`net.Socket`][].
+the specified file descriptor. This means that no `'open'` event will be
+emitted. Note that `fd` should be blocking; non-blocking `fd`s should be passed
+to [`net.Socket`][].
 
 If `autoClose` is false, then the file descriptor won't be closed, even if
 there's an error.  It is your responsibility to close it and make sure
@@ -550,7 +556,8 @@ Returns a new [`WriteStream`][] object. (See [Writable Stream][]).
 `options` may also include a `start` option to allow writing data at
 some position past the beginning of the file.  Modifying a file rather
 than replacing it may require a `flags` mode of `r+` rather than the
-default mode `w`. The `defaultEncoding` can be any one of those accepted by [`Buffer`][].
+default mode `w`. The `defaultEncoding` can be any one of those accepted by
+[`Buffer`][].
 
 If `autoClose` is set to true (default behavior) on `error` or `end`
 the file descriptor will be closed automatically. If `autoClose` is false,
@@ -597,7 +604,8 @@ added: v0.1.21
 deprecated: v1.0.0
 -->
 
-    Stability: 0 - Deprecated: Use [`fs.statSync()`][] or [`fs.accessSync()`][] instead.
+    Stability: 0 - Deprecated: Use [`fs.statSync()`][] or [`fs.accessSync()`][]
+    instead.
 
 * `path` {String | Buffer}
 
@@ -991,7 +999,7 @@ to a non-existent file. The exclusive flag may or may not work with network file
 systems.
 
 `flags` can also be a number as documented by open(2); commonly used constants
-are available from `require('constants')`.  On Windows, flags are translated to
+are available from `fs.constants`.  On Windows, flags are translated to
 their equivalent ones where applicable, e.g. `O_WRONLY` to `FILE_GENERIC_WRITE`,
 or `O_EXCL|O_CREAT` to `CREATE_NEW`, as accepted by CreateFileW.
 
@@ -1294,11 +1302,11 @@ added: v0.1.31
 * `callback` {Function}
 
 Asynchronous symlink(2). No arguments other than a possible exception are given
-to the completion callback.
-The `type` argument can be set to `'dir'`, `'file'`, or `'junction'` (default
-is `'file'`) and is only available on Windows (ignored on other platforms).
-Note that Windows junction points require the destination path to be absolute.  When using
-`'junction'`, the `target` argument will automatically be normalized to absolute path.
+to the completion callback. The `type` argument can be set to `'dir'`,
+`'file'`, or `'junction'` (default is `'file'`) and is only available on
+Windows (ignored on other platforms). Note that Windows junction points require
+the destination path to be absolute. When using `'junction'`, the `target`
+argument will automatically be normalized to absolute path.
 
 Here is an example below:
 
@@ -1543,9 +1551,9 @@ _Note: when an `fs.watchFile` operation results in an `ENOENT` error, it will
  of zero. If the file is created later on, the listener will be called again,
  with the latest stat objects. This is a change in functionality since v0.10._
 
-_Note: [`fs.watch()`][] is more efficient than `fs.watchFile` and `fs.unwatchFile`.
-`fs.watch` should be used instead of `fs.watchFile` and `fs.unwatchFile`
-when possible._
+_Note: [`fs.watch()`][] is more efficient than `fs.watchFile` and
+`fs.unwatchFile`. `fs.watch` should be used instead of `fs.watchFile` and
+`fs.unwatchFile` when possible._
 
 ## fs.write(fd, buffer, offset, length[, position], callback)
 <!-- YAML
@@ -1693,6 +1701,226 @@ added: v0.11.5
 
 Synchronous versions of [`fs.write()`][]. Returns the number of bytes written.
 
+## FS Constants
+
+The following constants are exported by `fs.constants`. **Note:** Not every
+constant will be available on every operating system.
+
+### File Access Constants
+
+The following constants are meant for use with [`fs.access()`][].
+
+<table>
+  <tr>
+    <th>Constant</th>
+    <th>Description</th>
+  </tr>
+  <tr>
+    <td><code>F_OK</code></td>
+    <td>Flag indicating that the file is visible to the calling process.</td>
+  </tr>
+  <tr>
+    <td><code>R_OK</code></td>
+    <td>Flag indicating that the file can be read by the calling process.</td>
+  </tr>
+  <tr>
+    <td><code>W_OK</code></td>
+    <td>Flag indicating that the file can be written by the calling
+    process.</td>
+  </tr>
+  <tr>
+    <td><code>X_OK</code></td>
+    <td>Flag indicating that the file can be executed by the calling
+    process.</td>
+  </tr>
+</table>
+
+### File Open Constants
+
+The following constants are meant for use with `fs.open()`.
+
+<table>
+  <tr>
+    <th>Constant</th>
+    <th>Description</th>
+  </tr>
+  <tr>
+    <td><code>O_RDONLY</code></td>
+    <td>Flag indicating to open a file for read-only access.</td>
+  </tr>
+  <tr>
+    <td><code>O_WRONLY</code></td>
+    <td>Flag indicating to open a file for write-only access.</td>
+  </tr>
+  <tr>
+    <td><code>O_RDWR</code></td>
+    <td>Flag indicating to open a file for read-write access.</td>
+  </tr>
+  <tr>
+    <td><code>O_CREAT</code></td>
+    <td>Flag indicating to create the file if it does not already exist.</td>
+  </tr>
+  <tr>
+    <td><code>O_EXCL</code></td>
+    <td>Flag indicating that opening a file should fail if the
+    <code>O_CREAT</code> flag is set and the file already exists.</td>
+  </tr>
+  <tr>
+    <td><code>O_NOCTTY</code></td>
+    <td>Flag indicating that if path identifies a terminal device, opening the
+    path shall not cause that terminal to become the controlling terminal for
+    the process (if the process does not already have one).</td>
+  </tr>
+  <tr>
+    <td><code>O_TRUNC</code></td>
+    <td>Flag indicating that if the file exists and is a regular file, and the
+    file is opened successfully for write access, its length shall be truncated
+    to zero.</td>
+  </tr>
+  <tr>
+    <td><code>O_APPEND</code></td>
+    <td>Flag indicating that data will be appended to the end of the file.</td>
+  </tr>
+  <tr>
+    <td><code>O_DIRECTORY</code></td>
+    <td>Flag indicating that the open should fail if the path is not a
+    directory.</td>
+  </tr>
+  <tr>
+  <td><code>O_NOATIME</code></td>
+    <td>Flag indicating reading accesses to the file system will no longer
+    result in an update to the `atime` information associated with the file.
+    This flag is available on Linux operating systems only.</td>
+  </tr>
+  <tr>
+    <td><code>O_NOFOLLOW</code></td>
+    <td>Flag indicating that the open should fail if the path is a symbolic
+    link.</td>
+  </tr>
+  <tr>
+    <td><code>O_SYNC</code></td>
+    <td>Flag indicating that the file is opened for synchronous I/O.</td>
+  </tr>
+  <tr>
+    <td><code>O_SYMLINK</code></td>
+    <td>Flag indicating to open the symbolic link itself rather than the
+    resource it is pointing to.</td>
+  </tr>
+  <tr>
+    <td><code>O_DIRECT</code></td>
+    <td>When set, an attempt will be made to minimize caching effects of file
+    I/O.</td>
+  </tr>
+  <tr>
+    <td><code>O_NONBLOCK</code></td>
+    <td>Flag indicating to open the file in nonblocking mode when possible.</td>
+  </tr>
+</table>
+
+### File Type Constants
+
+The following constants are meant for use with the [`fs.Stats`][] object's
+`mode` property for determining a file's type.
+
+<table>
+  <tr>
+    <th>Constant</th>
+    <th>Description</th>
+  </tr>
+  <tr>
+    <td><code>S_IFMT</code></td>
+    <td>Bit mask used to extract the file type code.</td>
+  </tr>
+  <tr>
+    <td><code>S_IFREG</code></td>
+    <td>File type constant for a regular file.</td>
+  </tr>
+  <tr>
+    <td><code>S_IFDIR</code></td>
+    <td>File type constant for a directory.</td>
+  </tr>
+  <tr>
+    <td><code>S_IFCHR</code></td>
+    <td>File type constant for a character-oriented device file.</td>
+  </tr>
+  <tr>
+    <td><code>S_IFBLK</code></td>
+    <td>File type constant for a block-oriented device file.</td>
+  </tr>
+  <tr>
+    <td><code>S_IFIFO</code></td>
+    <td>File type constant for a FIFO/pipe.</td>
+  </tr>
+  <tr>
+    <td><code>S_IFLNK</code></td>
+    <td>File type constant for a symbolic link.</td>
+  </tr>
+  <tr>
+    <td><code>S_IFSOCK</code></td>
+    <td>File type constant for a socket.</td>
+  </tr>
+</table>
+
+### File Mode Constants
+
+The following constants are meant for use with the [`fs.Stats`][] object's
+`mode` property for determining the access permissions for a file.
+
+<table>
+  <tr>
+    <th>Constant</th>
+    <th>Description</th>
+  </tr>
+  <tr>
+    <td><code>S_IRWXU</code></td>
+    <td>File mode indicating readable, writable and executable by owner.</td>
+  </tr>
+  <tr>
+    <td><code>S_IRUSR</code></td>
+    <td>File mode indicating readable by owner.</td>
+  </tr>
+  <tr>
+    <td><code>S_IWUSR</code></td>
+    <td>File mode indicating writable by owner.</td>
+  </tr>
+  <tr>
+    <td><code>S_IXUSR</code></td>
+    <td>File mode indicating executable by owner.</td>
+  </tr>
+  <tr>
+    <td><code>S_IRWXG</code></td>
+    <td>File mode indicating readable, writable and executable by group.</td>
+  </tr>
+  <tr>
+    <td><code>S_IRGRP</code></td>
+    <td>File mode indicating readable by group.</td>
+  </tr>
+  <tr>
+    <td><code>S_IWGRP</code></td>
+    <td>File mode indicating writable by group.</td>
+  </tr>
+  <tr>
+    <td><code>S_IXGRP</code></td>
+    <td>File mode indicating executable by group.</td>
+  </tr>
+  <tr>
+    <td><code>S_IRWXO</code></td>
+    <td>File mode indicating readable, writable and executable by others.</td>
+  </tr>
+  <tr>
+    <td><code>S_IROTH</code></td>
+    <td>File mode indicating readable by others.</td>
+  </tr>
+  <tr>
+    <td><code>S_IWOTH</code></td>
+    <td>File mode indicating writable by others.</td>
+  </tr>
+  <tr>
+    <td><code>S_IXOTH</code></td>
+    <td>File mode indicating executable by others.</td>
+  </tr>
+</table>
+
 [`Buffer.byteLength`]: buffer.html#buffer_class_method_buffer_bytelength_string_encoding
 [`Buffer`]: buffer.html#buffer_buffer
 [Caveats]: #fs_caveats
@@ -1726,9 +1954,12 @@ Synchronous versions of [`fs.write()`][]. Returns the number of bytes written.
 [Writable Stream]: stream.html#stream_class_stream_writable
 [inode]: http://www.linux.org/threads/intro-to-inodes.4130
 [FS Constants]: #fs_fs_constants
+<<<<<<< HEAD
 [`inotify`]: http://man7.org/linux/man-pages/man7/inotify.7.html
 [`kqueue`]: https://www.freebsd.org/cgi/man.cgi?kqueue
 [`FSEvents`]: https://developer.apple.com/library/mac/documentation/Darwin/Conceptual/FSEvents_ProgGuide/Introduction/Introduction.html#//apple_ref/doc/uid/TP40005289-CH1-SW1
 [`event ports`]: http://illumos.org/man/port_create
 [`ReadDirectoryChangesW`]: https://msdn.microsoft.com/en-us/library/windows/desktop/aa365465%28v=vs.85%29.aspx
 [`AHAFS`]: https://www.ibm.com/developerworks/aix/library/au-aix_event_infrastructure/
+=======
+>>>>>>> dcccbfd... src: refactor require('constants')