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1var Transform = require('readable-stream/transform')
2  , inherits  = require('util').inherits
3  , xtend     = require('xtend')
4
5function DestroyableTransform(opts) {
6  Transform.call(this, opts)
7  this._destroyed = false
8}
9
10inherits(DestroyableTransform, Transform)
11
12DestroyableTransform.prototype.destroy = function(err) {
13  if (this._destroyed) return
14  this._destroyed = true
15
16  var self = this
17  process.nextTick(function() {
18    if (err)
19      self.emit('error', err)
20    self.emit('close')
21  })
22}
23
24// a noop _transform function
25function noop (chunk, enc, callback) {
26  callback(null, chunk)
27}
28
29
30// create a new export function, used by both the main export and
31// the .ctor export, contains common logic for dealing with arguments
32function through2 (construct) {
33  return function (options, transform, flush) {
34    if (typeof options == 'function') {
35      flush     = transform
36      transform = options
37      options   = {}
38    }
39
40    if (typeof transform != 'function')
41      transform = noop
42
43    if (typeof flush != 'function')
44      flush = null
45
46    return construct(options, transform, flush)
47  }
48}
49
50
51// main export, just make me a transform stream!
52module.exports = through2(function (options, transform, flush) {
53  var t2 = new DestroyableTransform(options)
54
55  t2._transform = transform
56
57  if (flush)
58    t2._flush = flush
59
60  return t2
61})
62
63
64// make me a reusable prototype that I can `new`, or implicitly `new`
65// with a constructor call
66module.exports.ctor = through2(function (options, transform, flush) {
67  function Through2 (override) {
68    if (!(this instanceof Through2))
69      return new Through2(override)
70
71    this.options = xtend(options, override)
72
73    DestroyableTransform.call(this, this.options)
74  }
75
76  inherits(Through2, DestroyableTransform)
77
78  Through2.prototype._transform = transform
79
80  if (flush)
81    Through2.prototype._flush = flush
82
83  return Through2
84})
85
86
87module.exports.obj = through2(function (options, transform, flush) {
88  var t2 = new DestroyableTransform(xtend({ objectMode: true, highWaterMark: 16 }, options))
89
90  t2._transform = transform
91
92  if (flush)
93    t2._flush = flush
94
95  return t2
96})
97