# All files / tar/lib header.js

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100% Branches 120/120
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100% Lines 159/159

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     'use strict'
    // parse a 512-byte header block to a data object, or vice-versa
    // encode returns `true` if a pax extended header is needed, because
    // the data could not be faithfully encoded in a simple header.
    // (Also, check header.needPax to see if it needs a pax header.)

    const types = require('./types.js')
    const pathModule = require('path')
    const large = require('./large-numbers.js')

    const TYPE = Symbol('type')

    class Header {
      constructor (data, off) {
        this.cksumValid = false
        this.needPax = false
        this.nullBlock = false

        this.block = null
        this.path = null
        this.mode = null
        this.uid = null
        this.gid = null
        this.size = null
        this.mtime = null
        this.cksum = null
        this[TYPE] = '0'
        this.linkpath = null
        this.uname = null
        this.gname = null
        this.devmaj = 0
        this.devmin = 0
        this.atime = null
        this.ctime = null

        if (Buffer.isBuffer(data)) {
          this.decode(data, off || 0)
        } else if (data)
          this.set(data)
      }

      decode (buf, off) {
        if (!off)
          off = 0

        if (!buf || !(buf.length >= off + 512))
          throw new Error('need 512 bytes for header')

        this.path = decString(buf, off, 100)
        this.mode = decNumber(buf, off + 100, 8)
        this.uid = decNumber(buf, off + 108, 8)
        this.gid = decNumber(buf, off + 116, 8)
        this.size = decNumber(buf, off + 124, 12)
        this.mtime = decDate(buf, off + 136, 12)
        this.cksum = decNumber(buf, off + 148, 12)

        // old tar versions marked dirs as a file with a trailing /
        this[TYPE] = decString(buf, off + 156, 1)
        if (this[TYPE] === '')
          this[TYPE] = '0'
        if (this[TYPE] === '0' && this.path.substr(-1) === '/')
          this[TYPE] = '5'

        // tar implementations sometimes incorrectly put the stat(dir).size
        // as the size in the tarball, even though Directory entries are
        // not able to have any body at all.  In the very rare chance that
        // it actually DOES have a body, we weren't going to do anything with
        // it anyway, and it'll just be a warning about an invalid header.
        if (this[TYPE] === '5')
          this.size = 0

        this.linkpath = decString(buf, off + 157, 100)
        if (buf.slice(off + 257, off + 265).toString() === 'ustar\u000000') {
          this.uname = decString(buf, off + 265, 32)
          this.gname = decString(buf, off + 297, 32)
          this.devmaj = decNumber(buf, off + 329, 8)
          this.devmin = decNumber(buf, off + 337, 8)
          if (buf[off + 475] !== 0) {
            // definitely a prefix, definitely >130 chars.
            const prefix = decString(buf, off + 345, 155)
            this.path = prefix + '/' + this.path
          } else {
            const prefix = decString(buf, off + 345, 130)
            if (prefix)
              this.path = prefix + '/' + this.path
            this.atime = decDate(buf, off + 476, 12)
            this.ctime = decDate(buf, off + 488, 12)
          }
        }

        let sum = 8 * 0x20
        for (let i = off; i < off + 148; i++) {
          sum += buf[i]
        }
        for (let i = off + 156; i < off + 512; i++) {
          sum += buf[i]
        }
        this.cksumValid = sum === this.cksum
        if (this.cksum === null && sum === 8 * 0x20)
          this.nullBlock = true
      }

      encode (buf, off) {
        if (!buf) {
          buf = this.block = Buffer.alloc(512)
          off = 0
        }

        if (!off)
          off = 0

        if (!(buf.length >= off + 512))
          throw new Error('need 512 bytes for header')

        const prefixSize = this.ctime || this.atime ? 130 : 155
        const split = splitPrefix(this.path || '', prefixSize)
        const path = split[0]
        const prefix = split[1]
        this.needPax = split[2]

        this.needPax = encString(buf, off, 100, path) || this.needPax
        this.needPax = encNumber(buf, off + 100, 8, this.mode) || this.needPax
        this.needPax = encNumber(buf, off + 108, 8, this.uid) || this.needPax
        this.needPax = encNumber(buf, off + 116, 8, this.gid) || this.needPax
        this.needPax = encNumber(buf, off + 124, 12, this.size) || this.needPax
        this.needPax = encDate(buf, off + 136, 12, this.mtime) || this.needPax
        buf[off + 156] = this[TYPE].charCodeAt(0)
        this.needPax = encString(buf, off + 157, 100, this.linkpath) || this.needPax
        buf.write('ustar\u000000', off + 257, 8)
        this.needPax = encString(buf, off + 265, 32, this.uname) || this.needPax
        this.needPax = encString(buf, off + 297, 32, this.gname) || this.needPax
        this.needPax = encNumber(buf, off + 329, 8, this.devmaj) || this.needPax
        this.needPax = encNumber(buf, off + 337, 8, this.devmin) || this.needPax
        this.needPax = encString(buf, off + 345, prefixSize, prefix) || this.needPax
        if (buf[off + 475] !== 0)
          this.needPax = encString(buf, off + 345, 155, prefix) || this.needPax
        else {
          this.needPax = encString(buf, off + 345, 130, prefix) || this.needPax
          this.needPax = encDate(buf, off + 476, 12, this.atime) || this.needPax
          this.needPax = encDate(buf, off + 488, 12, this.ctime) || this.needPax
        }

        let sum = 8 * 0x20
        for (let i = off; i < off + 148; i++) {
          sum += buf[i]
        }
        for (let i = off + 156; i < off + 512; i++) {
          sum += buf[i]
        }
        this.cksum = sum
        encNumber(buf, off + 148, 8, this.cksum)
        this.cksumValid = true

        return this.needPax
      }

      set (data) {
        for (let i in data) {
          if (data[i] !== null && data[i] !== undefined)
            this[i] = data[i]
        }
      }

      get type () {
        return types.name.get(this[TYPE]) || this[TYPE]
      }

      get typeKey () {
        return this[TYPE]
      }

      set type (type) {
        if (types.code.has(type))
          this[TYPE] = types.code.get(type)
        else
          this[TYPE] = type
      }
    }

    const splitPrefix = (p, prefixSize) => {
      const pathSize = 100
      let pp = p
      let prefix = ''
      let ret
      const root = pathModule.parse(p).root || '.'

      if (Buffer.byteLength(pp) < pathSize)
        ret = [pp, prefix, false]
      else {
        // first set prefix to the dir, and path to the base
        prefix = pathModule.dirname(pp)
        pp = pathModule.basename(pp)

        do {
          // both fit!
          if (Buffer.byteLength(pp) <= pathSize &&
              Buffer.byteLength(prefix) <= prefixSize)
            ret = [pp, prefix, false]

          // prefix fits in prefix, but path doesn't fit in path
          else if (Buffer.byteLength(pp) > pathSize &&
              Buffer.byteLength(prefix) <= prefixSize)
            ret = [pp.substr(0, pathSize - 1), prefix, true]

          else {
            // make path take a bit from prefix
            pp = pathModule.join(pathModule.basename(prefix), pp)
            prefix = pathModule.dirname(prefix)
          }
        } while (prefix !== root && !ret)

        // at this point, found no resolution, just truncate
        if (!ret)
          ret = [p.substr(0, pathSize - 1), '', true]
      }
      return ret
    }

    const decString = (buf, off, size) =>
      buf.slice(off, off + size).toString('utf8').replace(/\0.*/, '')

    const decDate = (buf, off, size) =>
      numToDate(decNumber(buf, off, size))

    const numToDate = num => num === null ? null : new Date(num * 1000)

    const decNumber = (buf, off, size) =>
      buf[off] & 0x80 ? large.parse(buf.slice(off, off + size))
        : decSmallNumber(buf, off, size)

    const nanNull = value => isNaN(value) ? null : value

    const decSmallNumber = (buf, off, size) =>
      nanNull(parseInt(
        buf.slice(off, off + size)
          .toString('utf8').replace(/\0.*$/, '').trim(), 8))

    // the maximum encodable as a null-terminated octal, by field size
    const MAXNUM = {
      12: 0o77777777777,
      8 : 0o7777777
    }

    const encNumber = (buf, off, size, number) =>
      number === null ? false :
      number > MAXNUM[size] || number < 0
        ? (large.encode(number, buf.slice(off, off + size)), true)
        : (encSmallNumber(buf, off, size, number), false)

    const encSmallNumber = (buf, off, size, number) =>
      buf.write(octalString(number, size), off, size, 'ascii')

    const octalString = (number, size) =>
      padOctal(Math.floor(number).toString(8), size)

    const padOctal = (string, size) =>
      (string.length === size - 1 ? string
      : new Array(size - string.length - 1).join('0') + string + ' ') + '\0'

    const encDate = (buf, off, size, date) =>
      date === null ? false :
      encNumber(buf, off, size, date.getTime() / 1000)

    // enough to fill the longest string we've got
    const NULLS = new Array(156).join('\0')
    // pad with nulls, return true if it's longer or non-ascii
    const encString = (buf, off, size, string) =>
      string === null ? false :
      (buf.write(string + NULLS, off, size, 'utf8'),
       string.length !== Buffer.byteLength(string) || string.length > size)

    module.exports = Header