git ssb

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var has = Object.prototype.hasOwnProperty
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function toArgString() {
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  return [].join.call(arguments)
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}
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module.exports = function (opts, fn /*, preArgs... */) {
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  var preArgs = [].slice.call(arguments, 2)
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  if (typeof opts === 'function') {
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    if (arguments.length >= 2) preArgs.unshift(fn)
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    fn = opts
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    opts = {}
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  }
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  var cache =
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    opts.cache === false ? null :
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    opts.cache === true || opts.cache == null ? new Storage() :
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    opts.cache
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  var callbacks = {/* arg: [callback] */}
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  var toString = opts.asString || toArgString
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  var memoized = function (/* args..., cb */) {
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    var args = [].slice.call(arguments)
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    var cb = args.pop()
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    var memo = toString.apply(this, args)
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    if (cache && cache.has(memo)) {
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      var self = this
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      return process.nextTick(function () {
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        if (cache.has(memo))
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          cb.call(self, null, cache.get(memo))
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        else
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          run.call(self, args, memo, cb)
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      })
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    }
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    run.call(this, args, memo, cb)
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  }
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  memoized.cache = cache
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  return memoized
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  function run(args, memo, cb) {
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    if (has.call(callbacks, memo))
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      return callbacks[memo].push([this, cb])
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    var cbs = callbacks[memo] = [[this, cb]]
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    fn.apply(this, preArgs.concat(args, function (err, result) {
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      if (!err && cache)
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        cache.set(memo, result)
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      while (cbs.length) {
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        cb = cbs.shift()
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        cb[1].call(cb[0], err, result)
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      }
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      delete callbacks[memo]
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    }))
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  }
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}
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function Storage() {
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  this.data = {}
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}
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Storage.prototype.has = function (key) {
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  return has.call(this.data, key)
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}
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Storage.prototype.get = function (key) {
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  return this.data[key]
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}
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Storage.prototype.set = function (key, value) {
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  this.data[key] = value
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}
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Storage.prototype.remove = function (key) {
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  delete this.data[key]
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}
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Storage.prototype.clear = function (key) {
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  this.data = {}
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}
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