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var fs = require('fs')
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var polyfills = require('./polyfills.js')
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var legacy = require('./legacy-streams.js')
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var clone = require('./clone.js')
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var util = require('util')
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/* istanbul ignore next - node 0.x polyfill */
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var gracefulQueue
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var previousSymbol
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/* istanbul ignore else - node 0.x polyfill */
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if (typeof Symbol === 'function' && typeof Symbol.for === 'function') {
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  gracefulQueue = Symbol.for('graceful-fs.queue')
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  // This is used in testing by future versions
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  previousSymbol = Symbol.for('graceful-fs.previous')
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} else {
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  gracefulQueue = '___graceful-fs.queue'
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  previousSymbol = '___graceful-fs.previous'
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}
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function noop () {}
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var debug = noop
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if (util.debuglog)
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  debug = util.debuglog('gfs4')
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else if (/\bgfs4\b/i.test(process.env.NODE_DEBUG || ''))
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  debug = function() {
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    var m = util.format.apply(util, arguments)
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    m = 'GFS4: ' + m.split(/\n/).join('\nGFS4: ')
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    console.error(m)
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  }
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// Once time initialization
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if (!global[gracefulQueue]) {
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  // This queue can be shared by multiple loaded instances
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  var queue = []
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  Object.defineProperty(global, gracefulQueue, {
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    get: function() {
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      return queue
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    }
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  })
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  // Patch fs.close/closeSync to shared queue version, because we need
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  // to retry() whenever a close happens *anywhere* in the program.
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  // This is essential when multiple graceful-fs instances are
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  // in play at the same time.
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  fs.close = (function (fs$close) {
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    function close (fd, cb) {
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      return fs$close.call(fs, fd, function (err) {
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        // This function uses the graceful-fs shared queue
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        if (!err) {
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          retry()
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        }
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        if (typeof cb === 'function')
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          cb.apply(this, arguments)
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      })
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    }
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    Object.defineProperty(close, previousSymbol, {
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      value: fs$close
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    })
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    return close
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  })(fs.close)
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  fs.closeSync = (function (fs$closeSync) {
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    function closeSync (fd) {
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      // This function uses the graceful-fs shared queue
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      fs$closeSync.apply(fs, arguments)
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      retry()
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    }
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    Object.defineProperty(closeSync, previousSymbol, {
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      value: fs$closeSync
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    })
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    return closeSync
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  })(fs.closeSync)
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  if (/\bgfs4\b/i.test(process.env.NODE_DEBUG || '')) {
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    process.on('exit', function() {
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      debug(global[gracefulQueue])
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      require('assert').equal(global[gracefulQueue].length, 0)
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    })
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  }
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}
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module.exports = patch(clone(fs))
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if (process.env.TEST_GRACEFUL_FS_GLOBAL_PATCH && !fs.__patched) {
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    module.exports = patch(fs)
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    fs.__patched = true;
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}
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function patch (fs) {
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  // Everything that references the open() function needs to be in here
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  polyfills(fs)
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  fs.gracefulify = patch
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  fs.createReadStream = createReadStream
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  fs.createWriteStream = createWriteStream
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  var fs$readFile = fs.readFile
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  fs.readFile = readFile
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  function readFile (path, options, cb) {
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    if (typeof options === 'function')
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      cb = options, options = null
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    return go$readFile(path, options, cb)
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    function go$readFile (path, options, cb) {
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      return fs$readFile(path, options, function (err) {
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        if (err && (err.code === 'EMFILE' || err.code === 'ENFILE'))
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          enqueue([go$readFile, [path, options, cb]])
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        else {
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          if (typeof cb === 'function')
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            cb.apply(this, arguments)
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          retry()
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        }
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      })
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    }
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  }
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  var fs$writeFile = fs.writeFile
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  fs.writeFile = writeFile
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  function writeFile (path, data, options, cb) {
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    if (typeof options === 'function')
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      cb = options, options = null
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    return go$writeFile(path, data, options, cb)
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    function go$writeFile (path, data, options, cb) {
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      return fs$writeFile(path, data, options, function (err) {
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        if (err && (err.code === 'EMFILE' || err.code === 'ENFILE'))
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          enqueue([go$writeFile, [path, data, options, cb]])
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        else {
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          if (typeof cb === 'function')
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            cb.apply(this, arguments)
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          retry()
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        }
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      })
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    }
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  }
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  var fs$appendFile = fs.appendFile
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  if (fs$appendFile)
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    fs.appendFile = appendFile
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  function appendFile (path, data, options, cb) {
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    if (typeof options === 'function')
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      cb = options, options = null
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    return go$appendFile(path, data, options, cb)
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    function go$appendFile (path, data, options, cb) {
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      return fs$appendFile(path, data, options, function (err) {
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        if (err && (err.code === 'EMFILE' || err.code === 'ENFILE'))
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          enqueue([go$appendFile, [path, data, options, cb]])
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        else {
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          if (typeof cb === 'function')
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            cb.apply(this, arguments)
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          retry()
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        }
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      })
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    }
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  }
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  var fs$readdir = fs.readdir
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  fs.readdir = readdir
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  function readdir (path, options, cb) {
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    var args = [path]
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    if (typeof options !== 'function') {
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      args.push(options)
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    } else {
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      cb = options
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    }
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    args.push(go$readdir$cb)
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    return go$readdir(args)
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    function go$readdir$cb (err, files) {
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      if (files && files.sort)
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        files.sort()
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      if (err && (err.code === 'EMFILE' || err.code === 'ENFILE'))
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        enqueue([go$readdir, [args]])
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      else {
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        if (typeof cb === 'function')
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          cb.apply(this, arguments)
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        retry()
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      }
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    }
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  }
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  function go$readdir (args) {
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    return fs$readdir.apply(fs, args)
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  }
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  if (process.version.substr(0, 4) === 'v0.8') {
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    var legStreams = legacy(fs)
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    ReadStream = legStreams.ReadStream
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    WriteStream = legStreams.WriteStream
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  }
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  var fs$ReadStream = fs.ReadStream
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  if (fs$ReadStream) {
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    ReadStream.prototype = Object.create(fs$ReadStream.prototype)
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    ReadStream.prototype.open = ReadStream$open
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  }
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  var fs$WriteStream = fs.WriteStream
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  if (fs$WriteStream) {
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    WriteStream.prototype = Object.create(fs$WriteStream.prototype)
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    WriteStream.prototype.open = WriteStream$open
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  }
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  Object.defineProperty(fs, 'ReadStream', {
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    get: function () {
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      return ReadStream
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    },
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    set: function (val) {
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      ReadStream = val
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    },
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    enumerable: true,
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    configurable: true
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  })
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  Object.defineProperty(fs, 'WriteStream', {
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    get: function () {
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      return WriteStream
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    },
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    set: function (val) {
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      WriteStream = val
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    },
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    enumerable: true,
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    configurable: true
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  })
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  // legacy names
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  var FileReadStream = ReadStream
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  Object.defineProperty(fs, 'FileReadStream', {
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    get: function () {
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      return FileReadStream
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    },
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    set: function (val) {
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      FileReadStream = val
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    },
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    enumerable: true,
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    configurable: true
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  })
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  var FileWriteStream = WriteStream
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  Object.defineProperty(fs, 'FileWriteStream', {
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    get: function () {
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      return FileWriteStream
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    },
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    set: function (val) {
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      FileWriteStream = val
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    },
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    enumerable: true,
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    configurable: true
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  })
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  function ReadStream (path, options) {
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    if (this instanceof ReadStream)
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      return fs$ReadStream.apply(this, arguments), this
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    else
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      return ReadStream.apply(Object.create(ReadStream.prototype), arguments)
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  }
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  function ReadStream$open () {
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    var that = this
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    open(that.path, that.flags, that.mode, function (err, fd) {
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      if (err) {
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        if (that.autoClose)
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          that.destroy()
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        that.emit('error', err)
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      } else {
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        that.fd = fd
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        that.emit('open', fd)
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        that.read()
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      }
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    })
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  }
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  function WriteStream (path, options) {
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    if (this instanceof WriteStream)
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      return fs$WriteStream.apply(this, arguments), this
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    else
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      return WriteStream.apply(Object.create(WriteStream.prototype), arguments)
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  }
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  function WriteStream$open () {
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    var that = this
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    open(that.path, that.flags, that.mode, function (err, fd) {
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      if (err) {
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        that.destroy()
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        that.emit('error', err)
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      } else {
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        that.fd = fd
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        that.emit('open', fd)
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      }
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    })
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  }
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  function createReadStream (path, options) {
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    return new fs.ReadStream(path, options)
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  }
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  function createWriteStream (path, options) {
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    return new fs.WriteStream(path, options)
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  }
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  var fs$open = fs.open
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  fs.open = open
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  function open (path, flags, mode, cb) {
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    if (typeof mode === 'function')
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      cb = mode, mode = null
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    return go$open(path, flags, mode, cb)
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    function go$open (path, flags, mode, cb) {
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      return fs$open(path, flags, mode, function (err, fd) {
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        if (err && (err.code === 'EMFILE' || err.code === 'ENFILE'))
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          enqueue([go$open, [path, flags, mode, cb]])
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        else {
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          if (typeof cb === 'function')
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            cb.apply(this, arguments)
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          retry()
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        }
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      })
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    }
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  }
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  return fs
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}
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function enqueue (elem) {
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  debug('ENQUEUE', elem[0].name, elem[1])
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  global[gracefulQueue].push(elem)
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}
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function retry () {
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  var elem = global[gracefulQueue].shift()
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  if (elem) {
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    debug('RETRY', elem[0].name, elem[1])
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    elem[0].apply(null, elem[1])
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  }
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}