Add capability to instantiate an Address from public keys and a threshold

lib/address.js

@@ -1,5 +1,6 @@
 'use strict';
 
+var _ = require('lodash');
 var $ = require('./util/preconditions');
 var base58check = require('./encoding/base58check');
 var Networks = require('./networks');
@@ -42,6 +43,10 @@ function Address(data, network, type) {
     return new Address(data, network, type);
   }
 
+  if (_.isArray(data) && _.isNumber(network)) {
+    return Address.createMultisig(data, network, type);
+  }
+
   if (!data) {
     throw new TypeError('First argument is required, please include address data.');
   }
@@ -225,6 +230,19 @@ Address._transformScript = function(script, network){
   return info;
 };
 
+/**
+ * Creates a P2SH address from a set of public keys and a threshold.
+ *
+ * @param {Array} publicKeys
+ * @param {number} threshold
+ * @param {Network} network
+ * @return {Address}
+ */
+Address.createMultisig = function(publicKeys, threshold, network) {
+  var Script = require('./script');
+  return new Address(Script.buildMultisigOut(publicKeys, threshold), network || Networks.defaultNetwork);
+};
+
 /**
  * Internal function to transform a bitcoin address string
  *

lib/script/script.js

@@ -516,32 +516,30 @@ Script.prototype.removeCodeseparators = function() {
 /**
  * @returns a new Multisig output script for given public keys,
  * requiring m of those public keys to spend
- * @param {PublicKey[]} pubkeys - list of all public keys controlling the output
- * @param {number} m - amount of required signatures to spend the output
+ * @param {PublicKey[]} publicKeys - list of all public keys controlling the output
+ * @param {number} threshold - amount of required signatures to spend the output
  * @param {Object} [opts] - Several options:
  *        - noSorting: defaults to false, if true, don't sort the given
  *                      public keys before creating the script
  */
-Script.buildMultisigOut = function(pubkeys, m, opts) {
+Script.buildMultisigOut = function(publicKeys, threshold, opts) {
   opts = opts || {};
-  var s = new Script();
-  s.add(Opcode.smallInt(m));
-  pubkeys = _.map(pubkeys, function(pubkey) {
-    return PublicKey(pubkey);
-  });
-  var sorted = pubkeys;
+  var script = new Script();
+  script.add(Opcode.smallInt(threshold));
+  publicKeys = _.map(publicKeys, PublicKey);
+  var sorted = publicKeys;
   if (!opts.noSorting) {
-    sorted = _.sortBy(pubkeys, function(pubkey) {
-      return pubkey.toString('hex');
+    sorted = _.sortBy(publicKeys, function(publicKey) {
+      return publicKey.toString('hex');
     });
   }
   for (var i = 0; i < sorted.length; i++) {
-    var pubkey = sorted[i];
-    s.add(pubkey.toBuffer());
+    var publicKey = sorted[i];
+    script.add(publicKey.toBuffer());
   }
-  s.add(Opcode.smallInt(pubkeys.length));
-  s.add(Opcode.OP_CHECKMULTISIG);
-  return s;
+  script.add(Opcode.smallInt(publicKeys.length));
+  script.add(Opcode.OP_CHECKMULTISIG);
+  return script;
 };
 
 /**

test/address.js

@@ -448,4 +448,28 @@ describe('Address', function() {
     });
   });
 
+  describe('creating a P2SH address from public keys', function() {
+
+    var public1 = '02da5798ed0c055e31339eb9b5cef0d3c0ccdec84a62e2e255eb5c006d4f3e7f5b';
+    var public2 = '0272073bf0287c4469a2a011567361d42529cd1a72ab0d86aa104ecc89342ffeb0';
+    var public3 = '02738a516a78355db138e8119e58934864ce222c553a5407cf92b9c1527e03c1a2';
+    var publics = [public1, public2, public3];
+
+    it('can create an address from a set of public keys', function() {
+      var address = new Address(publics, 2);
+      address.toString().should.equal('3FtqPRirhPvrf7mVUSkygyZ5UuoAYrTW3y');
+    });
+
+    it('works on testnet also', function() {
+      var address = new Address(publics, 2, Networks.testnet);
+      address.toString().should.equal('2N7T3TAetJrSCruQ39aNrJvYLhG1LJosujf');
+    });
+
+    it('can also be created by Address.createMultisig', function() {
+      var address = Address.createMultisig(publics, 2);
+      var address2 = Address.createMultisig(publics, 2);
+      address.toString().should.equal(address2.toString());
+    });
+  });
+
 });