git ssb

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'use strict'
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function id (e) { return e }
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var prop = require('../util/prop')
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module.exports = function asyncMap (map) {
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  if(!map) return id
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  map = prop(map)
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  var busy = false, abortCb, aborted
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  return function (read) {
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    return function next (abort, cb) {
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      if(aborted) return cb(aborted)
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      if(abort) {
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        aborted = abort
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        if(!busy) read(abort, function (err) {
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          //incase the source has already ended normally,
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          //we should pass our own error.
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          cb(abort)
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        })
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        else read(abort, function (err) {
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          //if we are still busy, wait for the mapper to complete.
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          if(busy) abortCb = cb
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          else cb(abort)
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        })
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      }
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      else
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        read(null, function (end, data) {
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          if(end) cb(end)
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          else if(aborted) cb(aborted)
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          else {
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            busy = true
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            map(data, function (err, data) {
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              busy = false
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              if(aborted) {
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                cb(aborted)
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                abortCb && abortCb(aborted)
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              }
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              else if(err) next (err, cb)
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              else cb(null, data)
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            })
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          }
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        })
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    }
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  }
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}
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