Appending to a tar file

tarappend.js

var tar = require('tar-stream')
var concat = require('concat-stream')
var assert = require('assert')

var pack1 = tar.pack()

pack1.entry({
  name: 'hello'
}, 'hello world')

pack1.finalize()

pack1.pipe(concat(function (buf1) {
  var extract = tar.extract()
  var pack2 = tar.pack()

  extract.on('entry', function(header, stream, callback) {
    // write the new entry to the pack stream
    stream.pipe(pack2.entry(header, callback))
  })

  extract.on('finish', function() {
    pack2.entry({
      name: 'addition'
    }, 'a file addition')

    // all entries done - lets finalize it
    pack2.finalize()
  })

  // pipe the old tarball to the extractor
  extract.end(buf1)

  // pipe the new tarball the another stream
  pack2.pipe(concat(function (buf2) {
    for (var i = 0; i < buf1.length; i++) {
      if (buf1[i] !== buf2[i]) {
        console.log('the start being different at position', i)
        break
      }
    }
    assert.equal(buf1.length, 2048, 'the first tar file must be 4 blocks long')
    assert.equal(buf2.length, 3072, 'the second tar file must be 6 blocks long')
    assert.deepEqual(buf1.slice(0, 1024), buf2.slice(0, 1024), 'the beginning of the tar files must be the same')
  }))
}))