AlkantarClanX12
Your IP : 3.141.47.163
// parse a 512-byte header block to a data object, or vice-versa
// If the data won't fit nicely in a simple header, then generate
// the appropriate extended header file, and return that.
module.exports = TarHeader
var tar = require("../tar.js")
, fields = tar.fields
, fieldOffs = tar.fieldOffs
, fieldEnds = tar.fieldEnds
, fieldSize = tar.fieldSize
, numeric = tar.numeric
, assert = require("assert").ok
, space = " ".charCodeAt(0)
, slash = "/".charCodeAt(0)
, bslash = process.platform === "win32" ? "\\".charCodeAt(0) : null
function TarHeader (block) {
if (!(this instanceof TarHeader)) return new TarHeader(block)
if (block) this.decode(block)
}
TarHeader.prototype =
{ decode : decode
, encode: encode
, calcSum: calcSum
, checkSum: checkSum
}
TarHeader.parseNumeric = parseNumeric
TarHeader.encode = encode
TarHeader.decode = decode
// note that this will only do the normal ustar header, not any kind
// of extended posix header file. If something doesn't fit comfortably,
// then it will set obj.needExtended = true, and set the block to
// the closest approximation.
function encode (obj) {
if (!obj && !(this instanceof TarHeader)) throw new Error(
"encode must be called on a TarHeader, or supplied an object")
obj = obj || this
var block = obj.block = new Buffer(512)
// if the object has a "prefix", then that's actually an extension of
// the path field.
if (obj.prefix) {
// console.error("%% header encoding, got a prefix", obj.prefix)
obj.path = obj.prefix + "/" + obj.path
// console.error("%% header encoding, prefixed path", obj.path)
obj.prefix = ""
}
obj.needExtended = false
if (obj.mode) {
if (typeof obj.mode === "string") obj.mode = parseInt(obj.mode, 8)
obj.mode = obj.mode & 0777
}
for (var f = 0; fields[f] !== null; f ++) {
var field = fields[f]
, off = fieldOffs[f]
, end = fieldEnds[f]
, ret
switch (field) {
case "cksum":
// special, done below, after all the others
break
case "prefix":
// special, this is an extension of the "path" field.
// console.error("%% header encoding, skip prefix later")
break
case "type":
// convert from long name to a single char.
var type = obj.type || "0"
if (type.length > 1) {
type = tar.types[obj.type]
if (!type) type = "0"
}
writeText(block, off, end, type)
break
case "path":
// uses the "prefix" field if > 100 bytes, but <= 255
var pathLen = Buffer.byteLength(obj.path)
, pathFSize = fieldSize[fields.path]
, prefFSize = fieldSize[fields.prefix]
// paths between 100 and 255 should use the prefix field.
// longer than 255
if (pathLen > pathFSize &&
pathLen <= pathFSize + prefFSize) {
// need to find a slash somewhere in the middle so that
// path and prefix both fit in their respective fields
var searchStart = pathLen - 1 - pathFSize
, searchEnd = prefFSize
, found = false
, pathBuf = new Buffer(obj.path)
for ( var s = searchStart
; (s <= searchEnd)
; s ++ ) {
if (pathBuf[s] === slash || pathBuf[s] === bslash) {
found = s
break
}
}
if (found !== false) {
prefix = pathBuf.slice(0, found).toString("utf8")
path = pathBuf.slice(found + 1).toString("utf8")
ret = writeText(block, off, end, path)
off = fieldOffs[fields.prefix]
end = fieldEnds[fields.prefix]
// console.error("%% header writing prefix", off, end, prefix)
ret = writeText(block, off, end, prefix) || ret
break
}
}
// paths less than 100 chars don't need a prefix
// and paths longer than 255 need an extended header and will fail
// on old implementations no matter what we do here.
// Null out the prefix, and fallthrough to default.
// console.error("%% header writing no prefix")
var poff = fieldOffs[fields.prefix]
, pend = fieldEnds[fields.prefix]
writeText(block, poff, pend, "")
// fallthrough
// all other fields are numeric or text
default:
ret = numeric[field]
? writeNumeric(block, off, end, obj[field])
: writeText(block, off, end, obj[field] || "")
break
}
obj.needExtended = obj.needExtended || ret
}
var off = fieldOffs[fields.cksum]
, end = fieldEnds[fields.cksum]
writeNumeric(block, off, end, calcSum.call(this, block))
return block
}
// if it's a negative number, or greater than will fit,
// then use write256.
var MAXNUM = { 12: 077777777777
, 11: 07777777777
, 8 : 07777777
, 7 : 0777777 }
function writeNumeric (block, off, end, num) {
var writeLen = end - off
, maxNum = MAXNUM[writeLen] || 0
num = num || 0
// console.error(" numeric", num)
if (num instanceof Date ||
Object.prototype.toString.call(num) === "[object Date]") {
num = num.getTime() / 1000
}
if (num > maxNum || num < 0) {
write256(block, off, end, num)
// need an extended header if negative or too big.
return true
}
// god, tar is so annoying
// if the string is small enough, you should put a space
// between the octal string and the \0, but if it doesn't
// fit, then don't.
var numStr = Math.floor(num).toString(8)
if (num < MAXNUM[writeLen - 1]) numStr += " "
// pad with "0" chars
if (numStr.length < writeLen) {
numStr = (new Array(writeLen - numStr.length).join("0")) + numStr
}
if (numStr.length !== writeLen - 1) {
throw new Error("invalid length: " + JSON.stringify(numStr) + "\n" +
"expected: "+writeLen)
}
block.write(numStr, off, writeLen, "utf8")
block[end - 1] = 0
}
function write256 (block, off, end, num) {
var buf = block.slice(off, end)
var positive = num >= 0
buf[0] = positive ? 0x80 : 0xFF
// get the number as a base-256 tuple
if (!positive) num *= -1
var tuple = []
do {
var n = num % 256
tuple.push(n)
num = (num - n) / 256
} while (num)
var bytes = tuple.length
var fill = buf.length - bytes
for (var i = 1; i < fill; i ++) {
buf[i] = positive ? 0 : 0xFF
}
// tuple is a base256 number, with [0] as the *least* significant byte
// if it's negative, then we need to flip all the bits once we hit the
// first non-zero bit. The 2's-complement is (0x100 - n), and the 1's-
// complement is (0xFF - n).
var zero = true
for (i = bytes; i > 0; i --) {
var byte = tuple[bytes - i]
if (positive) buf[fill + i] = byte
else if (zero && byte === 0) buf[fill + i] = 0
else if (zero) {
zero = false
buf[fill + i] = 0x100 - byte
} else buf[fill + i] = 0xFF - byte
}
}
function writeText (block, off, end, str) {
// strings are written as utf8, then padded with \0
var strLen = Buffer.byteLength(str)
, writeLen = Math.min(strLen, end - off)
// non-ascii fields need extended headers
// long fields get truncated
, needExtended = strLen !== str.length || strLen > writeLen
// write the string, and null-pad
if (writeLen > 0) block.write(str, off, writeLen, "utf8")
for (var i = off + writeLen; i < end; i ++) block[i] = 0
return needExtended
}
function calcSum (block) {
block = block || this.block
assert(Buffer.isBuffer(block) && block.length === 512)
if (!block) throw new Error("Need block to checksum")
// now figure out what it would be if the cksum was " "
var sum = 0
, start = fieldOffs[fields.cksum]
, end = fieldEnds[fields.cksum]
for (var i = 0; i < fieldOffs[fields.cksum]; i ++) {
sum += block[i]
}
for (var i = start; i < end; i ++) {
sum += space
}
for (var i = end; i < 512; i ++) {
sum += block[i]
}
return sum
}
function checkSum (block) {
var sum = calcSum.call(this, block)
block = block || this.block
var cksum = block.slice(fieldOffs[fields.cksum], fieldEnds[fields.cksum])
cksum = parseNumeric(cksum)
return cksum === sum
}
function decode (block) {
block = block || this.block
assert(Buffer.isBuffer(block) && block.length === 512)
this.block = block
this.cksumValid = this.checkSum()
var prefix = null
// slice off each field.
for (var f = 0; fields[f] !== null; f ++) {
var field = fields[f]
, val = block.slice(fieldOffs[f], fieldEnds[f])
switch (field) {
case "ustar":
// if not ustar, then everything after that is just padding.
if (val.toString() !== "ustar\0") {
this.ustar = false
return
} else {
// console.error("ustar:", val, val.toString())
this.ustar = val.toString()
}
break
// prefix is special, since it might signal the xstar header
case "prefix":
var atime = parseNumeric(val.slice(131, 131 + 12))
, ctime = parseNumeric(val.slice(131 + 12, 131 + 12 + 12))
if ((val[130] === 0 || val[130] === space) &&
typeof atime === "number" &&
typeof ctime === "number" &&
val[131 + 12] === space &&
val[131 + 12 + 12] === space) {
this.atime = atime
this.ctime = ctime
val = val.slice(0, 130)
}
prefix = val.toString("utf8").replace(/\0+$/, "")
// console.error("%% header reading prefix", prefix)
break
// all other fields are null-padding text
// or a number.
default:
if (numeric[field]) {
this[field] = parseNumeric(val)
} else {
this[field] = val.toString("utf8").replace(/\0+$/, "")
}
break
}
}
// if we got a prefix, then prepend it to the path.
if (prefix) {
this.path = prefix + "/" + this.path
// console.error("%% header got a prefix", this.path)
}
}
function parse256 (buf) {
// first byte MUST be either 80 or FF
// 80 for positive, FF for 2's comp
var positive
if (buf[0] === 0x80) positive = true
else if (buf[0] === 0xFF) positive = false
else return null
// build up a base-256 tuple from the least sig to the highest
var zero = false
, tuple = []
for (var i = buf.length - 1; i > 0; i --) {
var byte = buf[i]
if (positive) tuple.push(byte)
else if (zero && byte === 0) tuple.push(0)
else if (zero) {
zero = false
tuple.push(0x100 - byte)
} else tuple.push(0xFF - byte)
}
for (var sum = 0, i = 0, l = tuple.length; i < l; i ++) {
sum += tuple[i] * Math.pow(256, i)
}
return positive ? sum : -1 * sum
}
function parseNumeric (f) {
if (f[0] & 0x80) return parse256(f)
var str = f.toString("utf8").split("\0")[0].trim()
, res = parseInt(str, 8)
return isNaN(res) ? null : res
}