git ssb

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var readArray = exports.readArray = function (array) {
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  var i = 0
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  return function (end, cb) {
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    if(end)
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      return cb && cb(end)
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    cb(i >= array.length || null, array[i++])
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  }
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}
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var count = function () {
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  var i = 0
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  return function (end, cb) {
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    if(end) return cb && cb(end)
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    cb(null, i++)
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  }
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}
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var infinite = exports.infinite = 
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function (generate) {
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  generate = generate || Math.random
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  return function (end, cb) {
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    if(end) return cb && cb(end)
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    return cb(null, generate())
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  }
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}
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var defer = exports.defer = function () {
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  var _read, _cb, _end
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  var read = function (end, cb) {
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    if(_cb && !_read) throw new Error(
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      'do not read twice' +
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      'without waiting for callback'
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    )
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    if(_read) return _read(end, cb)
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    _end = end, _cb = cb
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  }
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  read.resolve = function (read) {
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    if(_read) throw new Error('already resolved')
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    _read = read
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    if(_cb) _read(_end, _cb)
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  }
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  read.abort = function(err) {
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    read.resolve(function (_, cb) {
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      cb(err || true)
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    })
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  }
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  return read
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}
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var PushBuffer = exports.PushBuffer = function () {
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  var buffer = [], cbs = [], waiting = [], ended
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  function drain() {
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    while(waiting.length && (buffer.length || ended)) {
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      var data = buffer.shift()
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      var cb   = cbs.shift()
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      waiting.shift()(ended, data)
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      cb && cb(ended)
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    }
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  }
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  function read (end, cb) {
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    ended = ended || end
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    waiting.push(cb)
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    drain()
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  }
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  read.push = function (data, cb) {
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    buffer.push(data); cbs.push(cb)
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    drain()
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  }
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  read.end = function (end, cb) {
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    if('function' === typeof end)
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      cb = end, end = true
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    ended = ended || end || true; cbs.push(cb)
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    drain()
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  }
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  return read
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}
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var depthFirst = exports.depthFirst =
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function (start, createStream) {
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  var reads = []
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  reads.unshift(createStream(start))
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  return function next (end, cb) {
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    if(!reads.length)
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      return cb(true)
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    reads[0](end, function (end, data) {
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      if(end) {
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        //if this stream has ended, go to the next queue
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        reads.shift()
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        return next(null, cb)
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      }
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      reads.unshift(createStream(data))
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      cb(end, data)
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    })
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  }
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}
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//width first is just like depth first,
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//but push each new stream onto the end of the queue
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var widthFirst = exports.widthFirst = 
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function (start, createStream) {
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  var reads = []
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  reads.push(createStream(start))
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  return function next (end, cb) {
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    if(!reads.length)
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      return cb(true)
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    reads[0](end, function (end, data) {
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      if(end) {
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        reads.shift()
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        return next(null, cb)
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      }
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      reads.push(createStream(data))
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      cb(end, data)
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    })
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  }
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}
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var leafFirst = exports.leafFirst = 
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function (start, createStream) {
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  var reads = []
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  var output = []
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  reads.push(createStream(start))
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  return function next (end, cb) {
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    reads[0](end, function (end, data) {
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      if(end) {
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        reads.shift()
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        if(!output.length)
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          return cb(true)
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        return cb(null, output.shift())
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      }
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      reads.unshift(createStream(data))
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      output.unshift(data)
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      next(null, cb)
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    })
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  }
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}
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