git ssb

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'use strict'
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module.exports = function drain (op, done) {
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  var read, abort
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  function sink (_read) {
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    read = _read
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    if(abort) return sink.abort()
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    //this function is much simpler to write if you
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    //just use recursion, but by using a while loop
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    //we do not blow the stack if the stream happens to be sync.
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    ;(function next() {
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        var loop = true, cbed = false
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        while(loop) {
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          cbed = false
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          read(null, function (end, data) {
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            cbed = true
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            if(end = end || abort) {
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              loop = false
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              if(done) done(end === true ? null : end)
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              else if(end && end !== true)
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                throw end
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            }
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            else if(op && false === op(data) || abort) {
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              loop = false
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              read(abort || true, done || function () {})
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            }
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            else if(!loop){
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              next()
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            }
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          })
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          if(!cbed) {
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            loop = false
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            return
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          }
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        }
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      })()
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  }
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  sink.abort = function (err, cb) {
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    if('function' == typeof err)
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      cb = err, err = true
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    abort = err || true
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    if(read) return read(abort, cb || function () {})
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  }
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  return sink
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}
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