polyfills.js

var fs = require('fs')
var constants = require('constants')

var origCwd = process.cwd
var cwd = null
process.cwd = function() {
  if (!cwd)
    cwd = origCwd.call(process)
  return cwd
}
var chdir = process.chdir
process.chdir = function(d) {
  cwd = null
  chdir.call(process, d)
}

// (re-)implement some things that are known busted or missing.

// lchmod, broken prior to 0.6.2
// back-port the fix here.
if (constants.hasOwnProperty('O_SYMLINK') &&
    process.version.match(/^v0\.6\.[0-2]|^v0\.5\./)) {
  fs.lchmod = function (path, mode, callback) {
    callback = callback || noop
    fs.open( path
           , constants.O_WRONLY | constants.O_SYMLINK
           , mode
           , function (err, fd) {
      if (err) {
        callback(err)
        return
      }
      // prefer to return the chmod error, if one occurs,
      // but still try to close, and report closing errors if they occur.
      fs.fchmod(fd, mode, function (err) {
        fs.close(fd, function(err2) {
          callback(err || err2)
        })
      })
    })
  }

  fs.lchmodSync = function (path, mode) {
    var fd = fs.openSync(path, constants.O_WRONLY | constants.O_SYMLINK, mode)

    // prefer to return the chmod error, if one occurs,
    // but still try to close, and report closing errors if they occur.
    var err, err2
    try {
      var ret = fs.fchmodSync(fd, mode)
    } catch (er) {
      err = er
    }
    try {
      fs.closeSync(fd)
    } catch (er) {
      err2 = er
    }
    if (err || err2) throw (err || err2)
    return ret
  }
}


// lutimes implementation, or no-op
if (!fs.lutimes) {
  if (constants.hasOwnProperty("O_SYMLINK")) {
    fs.lutimes = function (path, at, mt, cb) {
      fs.open(path, constants.O_SYMLINK, function (er, fd) {
        cb = cb || noop
        if (er) return cb(er)
        fs.futimes(fd, at, mt, function (er) {
          fs.close(fd, function (er2) {
            return cb(er || er2)
          })
        })
      })
    }

    fs.lutimesSync = function (path, at, mt) {
      var fd = fs.openSync(path, constants.O_SYMLINK)
        , err
        , err2
        , ret

      try {
        var ret = fs.futimesSync(fd, at, mt)
      } catch (er) {
        err = er
      }
      try {
        fs.closeSync(fd)
      } catch (er) {
        err2 = er
      }
      if (err || err2) throw (err || err2)
      return ret
    }

  } else if (fs.utimensat && constants.hasOwnProperty("AT_SYMLINK_NOFOLLOW")) {
    // maybe utimensat will be bound soonish?
    fs.lutimes = function (path, at, mt, cb) {
      fs.utimensat(path, at, mt, constants.AT_SYMLINK_NOFOLLOW, cb)
    }

    fs.lutimesSync = function (path, at, mt) {
      return fs.utimensatSync(path, at, mt, constants.AT_SYMLINK_NOFOLLOW)
    }

  } else {
    fs.lutimes = function (_a, _b, _c, cb) { process.nextTick(cb) }
    fs.lutimesSync = function () {}
  }
}


// https://github.com/isaacs/node-graceful-fs/issues/4
// Chown should not fail on einval or eperm if non-root.

fs.chown = chownFix(fs.chown)
fs.fchown = chownFix(fs.fchown)
fs.lchown = chownFix(fs.lchown)

fs.chownSync = chownFixSync(fs.chownSync)
fs.fchownSync = chownFixSync(fs.fchownSync)
fs.lchownSync = chownFixSync(fs.lchownSync)

function chownFix (orig) {
  if (!orig) return orig
  return function (target, uid, gid, cb) {
    return orig.call(fs, target, uid, gid, function (er, res) {
      if (chownErOk(er)) er = null
      cb(er, res)
    })
  }
}

function chownFixSync (orig) {
  if (!orig) return orig
  return function (target, uid, gid) {
    try {
      return orig.call(fs, target, uid, gid)
    } catch (er) {
      if (!chownErOk(er)) throw er
    }
  }
}

function chownErOk (er) {
  // if there's no getuid, or if getuid() is something other than 0,
  // and the error is EINVAL or EPERM, then just ignore it.
  // This specific case is a silent failure in cp, install, tar,
  // and most other unix tools that manage permissions.
  // When running as root, or if other types of errors are encountered,
  // then it's strict.
  if (!er || (!process.getuid || process.getuid() !== 0)
      && (er.code === "EINVAL" || er.code === "EPERM")) return true
}


// if lchmod/lchown do not exist, then make them no-ops
if (!fs.lchmod) {
  fs.lchmod = function (path, mode, cb) {
    process.nextTick(cb)
  }
  fs.lchmodSync = function () {}
}
if (!fs.lchown) {
  fs.lchown = function (path, uid, gid, cb) {
    process.nextTick(cb)
  }
  fs.lchownSync = function () {}
}



// on Windows, A/V software can lock the directory, causing this
// to fail with an EACCES or EPERM if the directory contains newly
// created files.  Try again on failure, for up to 1 second.
if (process.platform === "win32") {
  var rename_ = fs.rename
  fs.rename = function rename (from, to, cb) {
    var start = Date.now()
    rename_(from, to, function CB (er) {
      if (er
          && (er.code === "EACCES" || er.code === "EPERM")
          && Date.now() - start < 1000) {
        return rename_(from, to, CB)
      }
      cb(er)
    })
  }
}


// if read() returns EAGAIN, then just try it again.
var read = fs.read
fs.read = function (fd, buffer, offset, length, position, callback_) {
  var callback
  if (callback_ && typeof callback_ === 'function') {
    var eagCounter = 0
    callback = function (er, _, __) {
      if (er && er.code === 'EAGAIN' && eagCounter < 10) {
        eagCounter ++
        return read.call(fs, fd, buffer, offset, length, position, callback)
      }
      callback_.apply(this, arguments)
    }
  }
  return read.call(fs, fd, buffer, offset, length, position, callback)
}

var readSync = fs.readSync
fs.readSync = function (fd, buffer, offset, length, position) {
  var eagCounter = 0
  while (true) {
    try {
      return readSync.call(fs, fd, buffer, offset, length, position)
    } catch (er) {
      if (er.code === 'EAGAIN' && eagCounter < 10) {
        eagCounter ++
        continue
      }
      throw er
    }
  }
}