git ssb

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var pull = require('pull-stream')
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var Buffered = require('pull-buffered')
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var xtend = require('xtend')
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var headers = require('./headers')
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var mixinPax = function (header, pax) {
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  if (pax.path) header.name = pax.path
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  if (pax.linkpath) header.linkname = pax.linkpath
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  if (pax.size) header.size = parseInt(pax.size, 10)
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  header.pax = pax
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  return header
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}
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module.exports = function (opts) {
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  var b = Buffered()
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  var gnuLongPath, gnuLongLinkPath, pax, paxGlobal
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  opts = opts || {}
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  var _cb
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  var ended
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  var locked = false
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  function drainOverflow(size, cb) {
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    var len = 512 - (size % 512)
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    if (!len) return cb()
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    b.chunks(len)(null, function (end, data) {
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      if (end && end !== true) return cb(end)
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      cb()
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    })
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  }
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  var readNextHeader = b.chunks(512)
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  function readEntry(cb) {
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    if (locked) return _cb = cb
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    if (ended) return cb(ended)
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    readNextHeader(null, function (end, data) {
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      if (end) return cb(ended = end)
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      var header
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      try { header = headers.decode(data, opts.filenameEncoding) }
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      catch (err) { return cb(err) }
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      if (!header) return readEntry(cb)
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      if (header.type === 'gnu-long-path') {
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        return b.chunks(header.size)(null, function (end, data) {
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          if (end) return cb(end)
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          gnuLongPath = headers.decodeLongPath(data, opts.filenameEncoding)
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          drainOverflow(header.size, function (err) {
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            if (err) return cb(err)
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            readEntry(cb)
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          })
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        })
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      }
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      if (header.type === 'gnu-long-link-path') {
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        return b.chunks(header.size)(null, function (end, data) {
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          if (end) return cb(end)
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          gnuLongLinkPath = headers.decodeLongPath(data, opts.filenameEncoding)
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          drainOverflow(header.size, function (err) {
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            if (err) return cb(err)
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            readEntry(cb)
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          })
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        })
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      }
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      if (header.type === 'pax-global-header') {
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        return b.chunks(header.size)(null, function (end, data) {
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          if (end) return cb(end)
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          paxGlobal = headers.decodePax(data)
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          drainOverflow(header.size, function (err) {
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            if (err) return cb(err)
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            readEntry(cb)
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          })
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        })
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      }
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      if (header.type === 'pax-header') {
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        return b.chunks(header.size)(null, function (end, data) {
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          if (end) return cb(end)
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          pax = headers.decodePax(data)
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          if (paxGlobal) pax = xtend(paxGlobal, pax)
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          drainOverflow(header.size, function (err) {
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            if (err) return cb(err)
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            readEntry(cb)
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          })
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        })
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      }
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      if (gnuLongPath) {
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        header.name = gnuLongPath
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        gnuLongPath = null
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      }
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      if (gnuLongLinkPath) {
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        header.linkname = gnuLongLinkPath
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        gnuLongLinkPath = null
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      }
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      if (pax) {
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        header = mixinPax(header, pax)
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        pax = null
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      }
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      if (!header.size || header.type === 'directory') {
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        return cb(null, {
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          header: header,
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          read: pull.empty()
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        })
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      }
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      locked = true
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      var overflow = 512 - header.size % 512
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      var readBody = b.take(header.size)
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      var readOverflow = function () {
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        pull(
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          b.take(overflow),
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          pull.drain(null, function (err) {
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            if (err) ended = err
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            locked = false
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            var cb1
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            if (_cb) {
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              var cb1 = _cb
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              _cb = null
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              readEntry(cb1)
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            }
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          })
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        )
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      }
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      var readBodyWrapped = function (abort, cb) {
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        if (abort) return pull(
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          readBody,
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          pull.drain(null, function (err) {
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            if (err) return cb(err)
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            cb()
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            readOverflow()
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          })
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        )
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        readBody(null, function (end, data) {
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          if (end) readOverflow()
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          cb(end, data)
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        })
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      }
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      cb(null, {
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        header: header,
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        read: readBodyWrapped
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      })
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    })
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  }
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  return function (read) {
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    b(read)
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    return function (abort, cb) {
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      if (abort) return read(abort, cb)
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      readEntry(cb)
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    }
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  }
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}
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