encode special characters @*/+ in http tracker urls

Fixes https://github.com/feross/webtorrent/issues/196

lib/common.js

@@ -59,6 +59,10 @@ exports.querystringStringify = function (obj) {
   var saved = querystring.escape
   querystring.escape = escape // global
   var ret = querystring.stringify(obj)
+  ret = ret.replace(/[\@\*\/\+]/g, function (char) {
+    // `escape` doesn't encode the characters @*/+ so we do it manually
+    return '%' + char.charCodeAt(0).toString(16).toUpperCase()
+  })
   querystring.escape = saved
   return ret
 }

test/querystring.js

@@ -0,0 +1,16 @@
+var common = require('../lib/common')
+var test = require('tape')
+
+// https://github.com/feross/webtorrent/issues/196
+test('encode special chars +* in http tracker urls', function (t) {
+  var q = {
+    info_hash: new Buffer('a2a15537542b22925ad10486bf7a8b2a9c42f0d1', 'hex').toString('binary')
+  }
+  var encoded = 'info_hash=%A2%A1U7T%2B%22%92Z%D1%04%86%BFz%8B%2A%9CB%F0%D1'
+  t.equal(common.querystringStringify(q), encoded)
+
+  // sanity check that encode-decode matches up
+  t.deepEqual(common.querystringParse(common.querystringStringify(q)), q)
+
+  t.end()
+})