add async utils

lib/bcoin/utils.js

@@ -1366,3 +1366,44 @@ utils.ccmp = function(a, b) {
 
   return res === 0;
 };
+
+utils.iter = function iter(from, to, iter, callback) {
+  var pending = to - from;
+  var i;
+
+  callback = utils.asyncify(callback);
+
+  if (pending <= 0)
+    return callback();
+
+  function next(err) {
+    if (err)
+      return callback(err);
+    if (!--pending)
+      callback();
+  }
+
+  for (i = from; i < to; i++)
+    iter(i, next);
+};
+
+utils.forEach = function forEach(arr, iter, callback) {
+  var pending = arr.length;
+  var i;
+
+  callback = utils.asyncify(callback);
+
+  if (!pending)
+    return callback();
+
+  function next(err) {
+    if (err)
+      return callback(err);
+    if (!--pending)
+      callback();
+  }
+
+  arr.forEach(function(item) {
+    iter(item, next);
+  });
+};