secretz.js

/**
 An encrypted, gzipped tar file will be piped in on process.stdin. To beat this
 challenge, for each file in the tar input, print a hex-encoded md5 hash of the
 file contents followed by a single space followed by the filename, then a
 newline.

 You will receive the cipher name as process.argv[2] and the cipher passphrase as
 process.argv[3]. You can pass these arguments directly through to
 `crypto.createDecipher()`.

 The built-in zlib library you get when you `require('zlib')` has a
 `zlib.createGunzip()` that returns a stream for gunzipping.

 The `tar` module from npm has a `tar.Parse()` function that emits `'entry'`
 events for each file in the tar input. Each `entry` object is a readable stream
 of the file contents from the archive and:

 `entry.type` is the kind of file ('File', 'Directory', etc)
 `entry.path` is the file path

 Using the tar module looks like:

 var tar = require('tar');
 var parser = tar.Parse();
 parser.on('entry', function (e) {
        console.dir(e);
    });
 var fs = require('fs');
 fs.createReadStream('file.tar').pipe(parser);

 Use `crypto.createHash('md5', { encoding: 'hex' })` to generate a stream that
 outputs a hex md5 hash for the content written to it.

 */

var zlib = require('zlib');
var tar = require('tar');
var crypto = require('crypto');
var through = require('through');

var decrypt = crypto.createDecipher(process.argv[2], process.argv[3]);
var parser = tar.Parse();

parser.on('entry', function(e) {
	if (e.type == 'File') {

		var hash = crypto.createHash('md5', {encoding: 'hex'});

		e.pipe(hash).pipe(through(null, end)).pipe(process.stdout);

		function end() {
			this.queue(" " + e.path + "\n");
		}
	}
});

process.stdin.pipe(decrypt).pipe(zlib.createGunzip()).pipe(parser);