The Tor Browser: addon-sdk/source/lib/sdk/io/fs.js@129ffea94266 (annotated)

addon-sdk/source/lib/sdk/io/fs.js@129ffea94266 (annotated)

addon-sdk/source/lib/sdk/io/fs.js

Sat, 03 Jan 2015 20:18:00 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Sat, 03 Jan 2015 20:18:00 +0100
branch: TOR_BUG_3246
changeset 7: 129ffea94266
permissions: -rw-r--r--

Conditionally enable double key logic according to:
private browsing mode or privacy.thirdparty.isolate preference and
implement in GetCookieStringCommon and FindCookie where it counts...
With some reservations of how to convince FindCookie users to test
condition and pass a nullptr when disabling double key logic.

 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 "use strict";
 module.metadata = {
   "stability": "experimental"
 };
 const { Cc, Ci, CC } = require("chrome");
 const { setTimeout } = require("../timers");
 const { Stream, InputStream, OutputStream } = require("./stream");
 const { emit, on } = require("../event/core");
 const { Buffer } = require("./buffer");
 const { ns } = require("../core/namespace");
 const { Class } = require("../core/heritage");
 const nsILocalFile = CC("@mozilla.org/file/local;1", "nsILocalFile",
                         "initWithPath");
 const FileOutputStream = CC("@mozilla.org/network/file-output-stream;1",
                             "nsIFileOutputStream", "init");
 const FileInputStream = CC("@mozilla.org/network/file-input-stream;1",
                            "nsIFileInputStream", "init");
 const BinaryInputStream = CC("@mozilla.org/binaryinputstream;1",
                              "nsIBinaryInputStream", "setInputStream");
 const BinaryOutputStream = CC("@mozilla.org/binaryoutputstream;1",
                               "nsIBinaryOutputStream", "setOutputStream");
 const StreamPump = CC("@mozilla.org/network/input-stream-pump;1",
                       "nsIInputStreamPump", "init");
 const { createOutputTransport, createInputTransport } =
   Cc["@mozilla.org/network/stream-transport-service;1"].
   getService(Ci.nsIStreamTransportService);
 const { OPEN_UNBUFFERED } = Ci.nsITransport;
 const { REOPEN_ON_REWIND, DEFER_OPEN } = Ci.nsIFileInputStream;
 const { DIRECTORY_TYPE, NORMAL_FILE_TYPE } = Ci.nsIFile;
 const { NS_SEEK_SET, NS_SEEK_CUR, NS_SEEK_END } = Ci.nsISeekableStream;
 const FILE_PERMISSION = parseInt("0666", 8);
 const PR_UINT32_MAX = 0xfffffff;
 // Values taken from:
 // http://mxr.mozilla.org/mozilla-central/source/nsprpub/pr/include/prio.h#615
 const PR_RDONLY =       0x01;
 const PR_WRONLY =       0x02;
 const PR_RDWR =         0x04;
 const PR_CREATE_FILE =  0x08;
 const PR_APPEND =       0x10;
 const PR_TRUNCATE =     0x20;
 const PR_SYNC =         0x40;
 const PR_EXCL =         0x80;
 const FLAGS = {
   "r":                  PR_RDONLY,
   "r+":                 PR_RDWR,
   "w":                  PR_CREATE_FILE | PR_TRUNCATE | PR_WRONLY,
   "w+":                 PR_CREATE_FILE | PR_TRUNCATE | PR_RDWR,
   "a":                  PR_APPEND | PR_CREATE_FILE | PR_WRONLY,
   "a+":                 PR_APPEND | PR_CREATE_FILE | PR_RDWR
 };
 function accessor() {
   let map = new WeakMap();
   return function(fd, value) {
     if (value === null) map.delete(fd);
     if (value !== undefined) map.set(fd, value);
     return map.get(fd);
   }
 }
 let nsIFile = accessor();
 let nsIFileInputStream = accessor();
 let nsIFileOutputStream = accessor();
 let nsIBinaryInputStream = accessor();
 let nsIBinaryOutputStream = accessor();
 // Just a contstant object used to signal that all of the file
 // needs to be read.
 const ALL = new String("Read all of the file");
 function isWritable(mode) !!(mode & PR_WRONLY || mode & PR_RDWR)
 function isReadable(mode) !!(mode & PR_RDONLY || mode & PR_RDWR)
 function isString(value) typeof(value) === "string"
 function isFunction(value) typeof(value) === "function"
 function toArray(enumerator) {
   let value = [];
   while(enumerator.hasMoreElements())
     value.push(enumerator.getNext())
   return value
 }
 function getFileName(file) file.QueryInterface(Ci.nsIFile).leafName
 function remove(path, recursive) {
   let fd = new nsILocalFile(path)
   if (fd.exists()) {
     fd.remove(recursive || false);
   }
   else {
     throw FSError("remove", "ENOENT", 34, path);
   }
 }
 /**
  * Utility function to convert either an octal number or string
  * into an octal number
  * 0777 => 0777
  * "0644" => 0644
  */
 function Mode(mode, fallback) {
   return isString(mode) ? parseInt(mode, 8) : mode || fallback;
 }
 function Flags(flag) {
   return !isString(flag) ? flag :
          FLAGS[flag] || Error("Unknown file open flag: " + flag);
 }
 function FSError(op, code, errno, path, file, line) {
   let error = Error(code + ", " + op + " " + path, file, line);
   error.code = code;
   error.path = path;
   error.errno = errno;
   return error;
 }
 const ReadStream = Class({
   extends: InputStream,
   initialize: function initialize(path, options) {
     this.position = -1;
     this.length = -1;
     this.flags = "r";
     this.mode = FILE_PERMISSION;
     this.bufferSize = 64 * 1024;
     options = options || {};
     if ("flags" in options && options.flags)
       this.flags = options.flags;
     if ("bufferSize" in options && options.bufferSize)
       this.bufferSize = options.bufferSize;
     if ("length" in options && options.length)
       this.length = options.length;
     if ("position" in options && options.position !== undefined)
       this.position = options.position;
     let { flags, mode, position, length } = this;
     let fd = isString(path) ? openSync(path, flags, mode) : path;
     this.fd = fd;
     let input = nsIFileInputStream(fd);
     // Setting a stream position, unless it"s `-1` which means current position.
     if (position >= 0)
       input.QueryInterface(Ci.nsISeekableStream).seek(NS_SEEK_SET, position);
     // We use `nsIStreamTransportService` service to transform blocking
     // file input stream into a fully asynchronous stream that can be written
     // without blocking the main thread.
     let transport = createInputTransport(input, position, length, false);
     // Open an input stream on a transport. We don"t pass flags to guarantee
     // non-blocking stream semantics. Also we use defaults for segment size &
     // count.
     InputStream.prototype.initialize.call(this, {
       asyncInputStream: transport.openInputStream(null, 0, 0)
     });
     // Close file descriptor on end and destroy the stream.
     on(this, "end", _ => {
       this.destroy();
       emit(this, "close");
     });
     this.read();
   },
   destroy: function() {
     closeSync(this.fd);
     InputStream.prototype.destroy.call(this);
   }
 });
 exports.ReadStream = ReadStream;
 exports.createReadStream = function createReadStream(path, options) {
   return new ReadStream(path, options);
 };
 const WriteStream = Class({
   extends: OutputStream,
   initialize: function initialize(path, options) {
     this.drainable = true;
     this.flags = "w";
     this.position = -1;
     this.mode = FILE_PERMISSION;
     options = options || {};
     if ("flags" in options && options.flags)
       this.flags = options.flags;
     if ("mode" in options && options.mode)
       this.mode = options.mode;
     if ("position" in options && options.position !== undefined)
       this.position = options.position;
     let { position, flags, mode } = this;
     // If pass was passed we create a file descriptor out of it. Otherwise
     // we just use given file descriptor.
     let fd = isString(path) ? openSync(path, flags, mode) : path;
     this.fd = fd;
     let output = nsIFileOutputStream(fd);
     // Setting a stream position, unless it"s `-1` which means current position.
     if (position >= 0)
       output.QueryInterface(Ci.nsISeekableStream).seek(NS_SEEK_SET, position);
     // We use `nsIStreamTransportService` service to transform blocking
     // file output stream into a fully asynchronous stream that can be written
     // without blocking the main thread.
     let transport = createOutputTransport(output, position, -1, false);
     // Open an output stream on a transport. We don"t pass flags to guarantee
     // non-blocking stream semantics. Also we use defaults for segment size &
     // count.
     OutputStream.prototype.initialize.call(this, {
       asyncOutputStream: transport.openOutputStream(OPEN_UNBUFFERED, 0, 0),
       output: output
     });
     // For write streams "finish" basically means close.
     on(this, "finish", _ => {
        this.destroy();
        emit(this, "close");
     });
   },
   destroy: function() {
     OutputStream.prototype.destroy.call(this);
     closeSync(this.fd);
   }
 });
 exports.WriteStream = WriteStream;
 exports.createWriteStream = function createWriteStream(path, options) {
   return new WriteStream(path, options);
 };
 const Stats = Class({
   initialize: function initialize(path) {
     let file = new nsILocalFile(path);
     if (!file.exists()) throw FSError("stat", "ENOENT", 34, path);
     nsIFile(this, file);
   },
   isDirectory: function() nsIFile(this).isDirectory(),
   isFile: function() nsIFile(this).isFile(),
   isSymbolicLink: function() nsIFile(this).isSymlink(),
   get mode() nsIFile(this).permissions,
   get size() nsIFile(this).fileSize,
   get mtime() nsIFile(this).lastModifiedTime,
   isBlockDevice: function() nsIFile(this).isSpecial(),
   isCharacterDevice: function() nsIFile(this).isSpecial(),
   isFIFO: function() nsIFile(this).isSpecial(),
   isSocket: function() nsIFile(this).isSpecial(),
   // non standard
   get exists() nsIFile(this).exists(),
   get hidden() nsIFile(this).isHidden(),
   get writable() nsIFile(this).isWritable(),
   get readable() nsIFile(this).isReadable()
 });
 exports.Stats = Stats;
 const LStats = Class({
   extends: Stats,
   get size() this.isSymbolicLink() ? nsIFile(this).fileSizeOfLink :
                                      nsIFile(this).fileSize,
   get mtime() this.isSymbolicLink() ? nsIFile(this).lastModifiedTimeOfLink :
                                       nsIFile(this).lastModifiedTime,
   // non standard
   get permissions() this.isSymbolicLink() ? nsIFile(this).permissionsOfLink :
                                             nsIFile(this).permissions
 });
 const FStat = Class({
   extends: Stats,
   initialize: function initialize(fd) {
     nsIFile(this, nsIFile(fd));
   }
 });
 function noop() {}
 function Async(wrapped) {
   return function (path, callback) {
     let args = Array.slice(arguments);
     callback = args.pop();
     // If node is not given a callback argument
     // it just does not calls it.
     if (typeof(callback) !== "function") {
       args.push(callback);
       callback = noop;
     }
     setTimeout(function() {
       try {
         var result = wrapped.apply(this, args);
         if (result === undefined) callback(null);
         else callback(null, result);
       } catch (error) {
         callback(error);
       }
     }, 0);
   }
 }
 /**
  * Synchronous rename(2)
  */
 function renameSync(oldPath, newPath) {
   let source = new nsILocalFile(oldPath);
   let target = new nsILocalFile(newPath);
   if (!source.exists()) throw FSError("rename", "ENOENT", 34, oldPath);
   return source.moveTo(target.parent, target.leafName);
 };
 exports.renameSync = renameSync;
 /**
  * Asynchronous rename(2). No arguments other than a possible exception are
  * given to the completion callback.
  */
 let rename = Async(renameSync);
 exports.rename = rename;
 /**
  * Test whether or not the given path exists by checking with the file system.
  */
 function existsSync(path) {
   return new nsILocalFile(path).exists();
 }
 exports.existsSync = existsSync;
 let exists = Async(existsSync);
 exports.exists = exists;
 /**
  * Synchronous ftruncate(2).
  */
 function truncateSync(path, length) {
   let fd = openSync(path, "w");
   ftruncateSync(fd, length);
   closeSync(fd);
 }
 exports.truncateSync = truncateSync;
 /**
  * Asynchronous ftruncate(2). No arguments other than a possible exception are
  * given to the completion callback.
  */
 function truncate(path, length, callback) {
   open(path, "w", function(error, fd) {
     if (error) return callback(error);
     ftruncate(fd, length, function(error) {
       if (error) {
         closeSync(fd);
         callback(error);
       }
       else {
         close(fd, callback);
       }
     });
   });
 }
 exports.truncate = truncate;
 function ftruncate(fd, length, callback) {
   write(fd, new Buffer(length), 0, length, 0, function(error) {
     callback(error);
   });
 }
 exports.ftruncate = ftruncate;
 function ftruncateSync(fd, length = 0) {
   writeSync(fd, new Buffer(length), 0, length, 0);
 }
 exports.ftruncateSync = ftruncateSync;
 function chownSync(path, uid, gid) {
   throw Error("Not implemented yet!!");
 }
 exports.chownSync = chownSync;
 let chown = Async(chownSync);
 exports.chown = chown;
 function lchownSync(path, uid, gid) {
   throw Error("Not implemented yet!!");
 }
 exports.lchownSync = chownSync;
 let lchown = Async(lchown);
 exports.lchown = lchown;
 /**
  * Synchronous chmod(2).
  */
 function chmodSync (path, mode) {
   let file;
   try {
     file = new nsILocalFile(path);
   } catch(e) {
     throw FSError("chmod", "ENOENT", 34, path);
   }
   file.permissions = Mode(mode);
 }
 exports.chmodSync = chmodSync;
 /**
  * Asynchronous chmod(2). No arguments other than a possible exception are
  * given to the completion callback.
  */
 let chmod = Async(chmodSync);
 exports.chmod = chmod;
 /**
  * Synchronous chmod(2).
  */
 function fchmodSync(fd, mode) {
   throw Error("Not implemented yet!!");
 };
 exports.fchmodSync = fchmodSync;
 /**
  * Asynchronous chmod(2). No arguments other than a possible exception are
  * given to the completion callback.
  */
 let fchmod = Async(fchmodSync);
 exports.fchmod = fchmod;
 /**
  * Synchronous stat(2). Returns an instance of `fs.Stats`
  */
 function statSync(path) {
   return new Stats(path);
 };
 exports.statSync = statSync;
 /**
  * Asynchronous stat(2). The callback gets two arguments (err, stats) where
  * stats is a `fs.Stats` object. It looks like this:
  */
 let stat = Async(statSync);
 exports.stat = stat;
 /**
  * Synchronous lstat(2). Returns an instance of `fs.Stats`.
  */
 function lstatSync(path) {
   return new LStats(path);
 };
 exports.lstatSync = lstatSync;
 /**
  * Asynchronous lstat(2). The callback gets two arguments (err, stats) where
  * stats is a fs.Stats object. lstat() is identical to stat(), except that if
  * path is a symbolic link, then the link itself is stat-ed, not the file that
  * it refers to.
  */
 let lstat = Async(lstatSync);
 exports.lstat = lstat;
 /**
  * Synchronous fstat(2). Returns an instance of `fs.Stats`.
  */
 function fstatSync(fd) {
   return new FStat(fd);
 };
 exports.fstatSync = fstatSync;
 /**
  * Asynchronous fstat(2). The callback gets two arguments (err, stats) where
  * stats is a fs.Stats object.
  */
 let fstat = Async(fstatSync);
 exports.fstat = fstat;
 /**
  * Synchronous link(2).
  */
 function linkSync(source, target) {
   throw Error("Not implemented yet!!");
 };
 exports.linkSync = linkSync;
 /**
  * Asynchronous link(2). No arguments other than a possible exception are given
  * to the completion callback.
  */
 let link = Async(linkSync);
 exports.link = link;
 /**
  * Synchronous symlink(2).
  */
 function symlinkSync(source, target) {
   throw Error("Not implemented yet!!");
 };
 exports.symlinkSync = symlinkSync;
 /**
  * Asynchronous symlink(2). No arguments other than a possible exception are
  * given to the completion callback.
  */
 let symlink = Async(symlinkSync);
 exports.symlink = symlink;
 /**
  * Synchronous readlink(2). Returns the resolved path.
  */
 function readlinkSync(path) {
   return new nsILocalFile(path).target;
 };
 exports.readlinkSync = readlinkSync;
 /**
  * Asynchronous readlink(2). The callback gets two arguments
  * `(error, resolvedPath)`.
  */
 let readlink = Async(readlinkSync);
 exports.readlink = readlink;
 /**
  * Synchronous realpath(2). Returns the resolved path.
  */
 function realpathSync(path) {
   return new nsILocalFile(path).path;
 };
 exports.realpathSync = realpathSync;
 /**
  * Asynchronous realpath(2). The callback gets two arguments
  * `(err, resolvedPath)`.
  */
 let realpath = Async(realpathSync);
 exports.realpath = realpath;
 /**
  * Synchronous unlink(2).
  */
 let unlinkSync = remove;
 exports.unlinkSync = unlinkSync;
 /**
  * Asynchronous unlink(2). No arguments other than a possible exception are
  * given to the completion callback.
  */
 let unlink = Async(remove);
 exports.unlink = unlink;
 /**
  * Synchronous rmdir(2).
  */
 let rmdirSync = remove;
 exports.rmdirSync = rmdirSync;
 /**
  * Asynchronous rmdir(2). No arguments other than a possible exception are
  * given to the completion callback.
  */
 let rmdir = Async(rmdirSync);
 exports.rmdir = rmdir;
 /**
  * Synchronous mkdir(2).
  */
 function mkdirSync(path, mode) {
   try {
     return nsILocalFile(path).create(DIRECTORY_TYPE, Mode(mode));
   } catch (error) {
     // Adjust exception thorw to match ones thrown by node.
     if (error.name === "NS_ERROR_FILE_ALREADY_EXISTS") {
       let { fileName, lineNumber } = error;
       error = FSError("mkdir", "EEXIST", 47, path, fileName, lineNumber);
     }
     throw error;
   }
 };
 exports.mkdirSync = mkdirSync;
 /**
  * Asynchronous mkdir(2). No arguments other than a possible exception are
  * given to the completion callback.
  */
 let mkdir = Async(mkdirSync);
 exports.mkdir = mkdir;
 /**
  * Synchronous readdir(3). Returns an array of filenames excluding `"."` and
  * `".."`.
  */
 function readdirSync(path) {
   try {
     return toArray(new nsILocalFile(path).directoryEntries).map(getFileName);
   }
   catch (error) {
     // Adjust exception thorw to match ones thrown by node.
     if (error.name === "NS_ERROR_FILE_TARGET_DOES_NOT_EXIST" ||
         error.name === "NS_ERROR_FILE_NOT_FOUND")
     {
       let { fileName, lineNumber } = error;
       error = FSError("readdir", "ENOENT", 34, path, fileName, lineNumber);
     }
     throw error;
   }
 };
 exports.readdirSync = readdirSync;
 /**
  * Asynchronous readdir(3). Reads the contents of a directory. The callback
  * gets two arguments `(error, files)` where `files` is an array of the names
  * of the files in the directory excluding `"."` and `".."`.
  */
 let readdir = Async(readdirSync);
 exports.readdir = readdir;
 /**
  * Synchronous close(2).
  */
  function closeSync(fd) {
    let input = nsIFileInputStream(fd);
    let output = nsIFileOutputStream(fd);
    // Closing input stream and removing reference.
    if (input) input.close();
    // Closing output stream and removing reference.
    if (output) output.close();
    nsIFile(fd, null);
    nsIFileInputStream(fd, null);
    nsIFileOutputStream(fd, null);
    nsIBinaryInputStream(fd, null);
    nsIBinaryOutputStream(fd, null);
 };
 exports.closeSync = closeSync;
 /**
  * Asynchronous close(2). No arguments other than a possible exception are
  * given to the completion callback.
  */
 let close = Async(closeSync);
 exports.close = close;
 /**
  * Synchronous open(2).
  */
 function openSync(path, flags, mode) {
   let [ fd, flags, mode, file ] =
       [ { path: path }, Flags(flags), Mode(mode), nsILocalFile(path) ];
   nsIFile(fd, file);
   // If trying to open file for just read that does not exists
   // need to throw exception as node does.
   if (!file.exists() && !isWritable(flags))
     throw FSError("open", "ENOENT", 34, path);
   // If we want to open file in read mode we initialize input stream.
   if (isReadable(flags)) {
     let input = FileInputStream(file, flags, mode, DEFER_OPEN);
     nsIFileInputStream(fd, input);
   }
   // If we want to open file in write mode we initialize output stream for it.
   if (isWritable(flags)) {
     let output = FileOutputStream(file, flags, mode, DEFER_OPEN);
     nsIFileOutputStream(fd, output);
   }
   return fd;
 }
 exports.openSync = openSync;
 /**
  * Asynchronous file open. See open(2). Flags can be
  * `"r", "r+", "w", "w+", "a"`, or `"a+"`. mode defaults to `0666`.
  * The callback gets two arguments `(error, fd).
  */
 let open = Async(openSync);
 exports.open = open;
 /**
  * Synchronous version of buffer-based fs.write(). Returns the number of bytes
  * written.
  */
 function writeSync(fd, buffer, offset, length, position) {
   if (length + offset > buffer.length) {
     throw Error("Length is extends beyond buffer");
   }
   else if (length + offset !== buffer.length) {
     buffer = buffer.slice(offset, offset + length);
   }
   let writeStream = new WriteStream(fd, { position: position,
                                           length: length });
   let output = BinaryOutputStream(nsIFileOutputStream(fd));
   nsIBinaryOutputStream(fd, output);
   // We write content as a byte array as this will avoid any transcoding
   // if content was a buffer.
   output.writeByteArray(buffer.valueOf(), buffer.length);
   output.flush();
 };
 exports.writeSync = writeSync;
 /**
  * Write buffer to the file specified by fd.
  *
  * `offset` and `length` determine the part of the buffer to be written.
  *
  * `position` refers to the offset from the beginning of the file where this
  * data should be written. If `position` is `null`, the data will be written
  * at the current position. See pwrite(2).
  *
  * The callback will be given three arguments `(error, written, buffer)` where
  * written specifies how many bytes were written into buffer.
  *
  * Note that it is unsafe to use `fs.write` multiple times on the same file
  * without waiting for the callback.
  */
 function write(fd, buffer, offset, length, position, callback) {
   if (!Buffer.isBuffer(buffer)) {
     // (fd, data, position, encoding, callback)
     let encoding = null;
     [ position, encoding, callback ] = Array.slice(arguments, 1);
     buffer = new Buffer(String(buffer), encoding);
     offset = 0;
   } else if (length + offset > buffer.length) {
     throw Error("Length is extends beyond buffer");
   } else if (length + offset !== buffer.length) {
     buffer = buffer.slice(offset, offset + length);
   }
   let writeStream = new WriteStream(fd, { position: position,
                                           length: length });
   writeStream.on("error", callback);
   writeStream.write(buffer, function onEnd() {
     writeStream.destroy();
     if (callback)
       callback(null, buffer.length, buffer);
   });
 };
 exports.write = write;
 /**
  * Synchronous version of string-based fs.read. Returns the number of
  * bytes read.
  */
 function readSync(fd, buffer, offset, length, position) {
   let input = nsIFileInputStream(fd);
   // Setting a stream position, unless it"s `-1` which means current position.
   if (position >= 0)
     input.QueryInterface(Ci.nsISeekableStream).seek(NS_SEEK_SET, position);
   // We use `nsIStreamTransportService` service to transform blocking
   // file input stream into a fully asynchronous stream that can be written
   // without blocking the main thread.
   let binaryInputStream = BinaryInputStream(input);
   let count = length === ALL ? binaryInputStream.available() : length;
   if (offset === 0) binaryInputStream.readArrayBuffer(count, buffer.buffer);
   else {
     let chunk = new Buffer(count);
     binaryInputStream.readArrayBuffer(count, chunk.buffer);
     chunk.copy(buffer, offset);
   }
   return buffer.slice(offset, offset + count);
 };
 exports.readSync = readSync;
 /**
  * Read data from the file specified by `fd`.
  *
  * `buffer` is the buffer that the data will be written to.
  * `offset` is offset within the buffer where writing will start.
  *
  * `length` is an integer specifying the number of bytes to read.
  *
  * `position` is an integer specifying where to begin reading from in the file.
  * If `position` is `null`, data will be read from the current file position.
  *
  * The callback is given the three arguments, `(error, bytesRead, buffer)`.
  */
 function read(fd, buffer, offset, length, position, callback) {
   let bytesRead = 0;
   let readStream = new ReadStream(fd, { position: position, length: length });
   readStream.on("data", function onData(data) {
       data.copy(buffer, offset + bytesRead);
       bytesRead += data.length;
   });
   readStream.on("end", function onEnd() {
     callback(null, bytesRead, buffer);
     readStream.destroy();
   });
 };
 exports.read = read;
 /**
  * Asynchronously reads the entire contents of a file.
  * The callback is passed two arguments `(error, data)`, where data is the
  * contents of the file.
  */
 function readFile(path, encoding, callback) {
   if (isFunction(encoding)) {
     callback = encoding
     encoding = null
   }
   let buffer = null;
   try {
     let readStream = new ReadStream(path);
     readStream.on("data", function(data) {
       if (!buffer) buffer = data;
       else buffer = Buffer.concat([buffer, data], 2);
     });
     readStream.on("error", function onError(error) {
       callback(error);
     });
     readStream.on("end", function onEnd() {
       // Note: Need to destroy before invoking a callback
       // so that file descriptor is released.
       readStream.destroy();
       callback(null, buffer);
     });
   } catch (error) {
     setTimeout(callback, 0, error);
   }
 };
 exports.readFile = readFile;
 /**
  * Synchronous version of `fs.readFile`. Returns the contents of the path.
  * If encoding is specified then this function returns a string.
  * Otherwise it returns a buffer.
  */
 function readFileSync(path, encoding) {
   let fd = openSync(path, "r");
   let size = fstatSync(fd).size;
   let buffer = new Buffer(size);
   try {
     readSync(fd, buffer, 0, ALL, 0);
   }
   finally {
     closeSync(fd);
   }
   return buffer;
 };
 exports.readFileSync = readFileSync;
 /**
  * Asynchronously writes data to a file, replacing the file if it already
  * exists. data can be a string or a buffer.
  */
 function writeFile(path, content, encoding, callback) {
   if (!isString(path))
     throw new TypeError('path must be a string');
   try {
     if (isFunction(encoding)) {
       callback = encoding
       encoding = null
     }
     if (isString(content))
       content = new Buffer(content, encoding);
     let writeStream = new WriteStream(path);
     let error = null;
     writeStream.end(content, function() {
       writeStream.destroy();
       callback(error);
     });
     writeStream.on("error", function onError(reason) {
       error = reason;
       writeStream.destroy();
     });
   } catch (error) {
     callback(error);
   }
 };
 exports.writeFile = writeFile;
 /**
  * The synchronous version of `fs.writeFile`.
  */
 function writeFileSync(filename, data, encoding) {
   throw Error("Not implemented");
 };
 exports.writeFileSync = writeFileSync;
 function utimesSync(path, atime, mtime) {
   throw Error("Not implemented");
 }
 exports.utimesSync = utimesSync;
 let utimes = Async(utimesSync);
 exports.utimes = utimes;
 function futimesSync(fd, atime, mtime, callback) {
   throw Error("Not implemented");
 }
 exports.futimesSync = futimesSync;
 let futimes = Async(futimesSync);
 exports.futimes = futimes;
 function fsyncSync(fd, atime, mtime, callback) {
   throw Error("Not implemented");
 }
 exports.fsyncSync = fsyncSync;
 let fsync = Async(fsyncSync);
 exports.fsync = fsync;
 /**
  * Watch for changes on filename. The callback listener will be called each
  * time the file is accessed.
  *
  * The second argument is optional. The options if provided should be an object
  * containing two members a boolean, persistent, and interval, a polling value
  * in milliseconds. The default is { persistent: true, interval: 0 }.
  */
 function watchFile(path, options, listener) {
   throw Error("Not implemented");
 };
 exports.watchFile = watchFile;
 function unwatchFile(path, listener) {
   throw Error("Not implemented");
 }
 exports.unwatchFile = unwatchFile;
 function watch(path, options, listener) {
   throw Error("Not implemented");
 }
 exports.watch = watch;