extended-header.js

// An Entry consisting of:
//
// "%d %s=%s\n", <length>, <keyword>, <value>
//
// The length is a decimal number, and includes itself and the \n
// \0 does not terminate anything.  Only the length terminates the string.
// Numeric values are decimal strings.

module.exports = ExtendedHeader

var Entry = require("./entry.js")
  , inherits = require("inherits")
  , tar = require("../tar.js")
  , numeric = tar.numeric
  , keyTrans = { "SCHILY.dev": "dev"
               , "SCHILY.ino": "ino"
               , "SCHILY.nlink": "nlink" }

function ExtendedHeader () {
  Entry.apply(this, arguments)
  this.on("data", this._parse)
  this.fields = {}
  this._position = 0
  this._fieldPos = 0
  this._state = SIZE
  this._sizeBuf = []
  this._keyBuf = []
  this._valBuf = []
  this._size = -1
  this._key = ""
}

inherits(ExtendedHeader, Entry)
ExtendedHeader.prototype._parse = parse

var s = 0
  , states = ExtendedHeader.states = {}
  , SIZE = states.SIZE = s++
  , KEY  = states.KEY  = s++
  , VAL  = states.VAL  = s++
  , ERR  = states.ERR  = s++

Object.keys(states).forEach(function (s) {
  states[states[s]] = states[s]
})

states[s] = null

// char code values for comparison
var _0 = "0".charCodeAt(0)
  , _9 = "9".charCodeAt(0)
  , point = ".".charCodeAt(0)
  , a = "a".charCodeAt(0)
  , Z = "Z".charCodeAt(0)
  , a = "a".charCodeAt(0)
  , z = "z".charCodeAt(0)
  , space = " ".charCodeAt(0)
  , eq = "=".charCodeAt(0)
  , cr = "\n".charCodeAt(0)

function parse (c) {
  if (this._state === ERR) return

  for ( var i = 0, l = c.length
      ; i < l
      ; this._position++, this._fieldPos++, i++) {
    // console.error("top of loop, size="+this._size)

    var b = c[i]

    if (this._size >= 0 && this._fieldPos > this._size) {
      error(this, "field exceeds length="+this._size)
      return
    }

    switch (this._state) {
      case ERR: return

      case SIZE:
        // console.error("parsing size, b=%d, rest=%j", b, c.slice(i).toString())
        if (b === space) {
          this._state = KEY
          // this._fieldPos = this._sizeBuf.length
          this._size = parseInt(new Buffer(this._sizeBuf).toString(), 10)
          this._sizeBuf.length = 0
          continue
        }
        if (b < _0 || b > _9) {
          error(this, "expected [" + _0 + ".." + _9 + "], got " + b)
          return
        }
        this._sizeBuf.push(b)
        continue

      case KEY:
        // can be any char except =, not > size.
        if (b === eq) {
          this._state = VAL
          this._key = new Buffer(this._keyBuf).toString()
          if (keyTrans[this._key]) this._key = keyTrans[this._key]
          this._keyBuf.length = 0
          continue
        }
        this._keyBuf.push(b)
        continue

      case VAL:
        // field must end with cr
        if (this._fieldPos === this._size - 1) {
          // console.error("finished with "+this._key)
          if (b !== cr) {
            error(this, "expected \\n at end of field")
            return
          }
          var val = new Buffer(this._valBuf).toString()
          if (numeric[this._key]) {
            val = parseFloat(val)
          }
          this.fields[this._key] = val

          this._valBuf.length = 0
          this._state = SIZE
          this._size = -1
          this._fieldPos = -1
          continue
        }
        this._valBuf.push(b)
        continue
    }
  }
}

function error (me, msg) {
  msg = "invalid header: " + msg
      + "\nposition=" + me._position
      + "\nfield position=" + me._fieldPos

  me.error(msg)
  me.state = ERR
}