add static method for creating an AuditStream object from the results…

… of another

lib/auditstream.js

@@ -140,4 +140,27 @@ AuditStream.prototype._createResponseInput = function(challenge) {
   return crypto.createHash('sha256').update(challenge);
 };
 
+/**
+ * Returns a new instance from the predefined challenges and tree
+ * @param {Array} challenges - The precomputed challenges
+ * @param {Array} tree - The bottom leaves of the existing merkle tree
+ * @returns {AuditStream}
+ */
+AuditStream.fromRecords = function(challenges, tree) {
+  assert(Array.isArray(challenges), 'Invalid challenges supplied');
+  assert(Array.isArray(tree), 'Invalid tree supplied');
+  assert(
+    tree.length === utils.getNextPowerOfTwo(challenges.length),
+    'Challenges and tree do not match'
+  );
+
+  var auditor = new AuditStream(challenges.length);
+
+  auditor._challenges = challenges;
+  auditor._tree = new MerkleTree(tree, utils.rmd160sha256);
+  auditor._finished = true;
+
+  return auditor;
+};
+
 module.exports = AuditStream;

package.json

@@ -1,6 +1,6 @@
 {
   "name": "storj",
-  "version": "0.6.10",
+  "version": "0.6.11",
   "description": "implementation of the storj protocol for node.js and the browser",
   "main": "index.js",
   "directories": {

test/auditstream.unit.js

@@ -82,6 +82,40 @@ describe('AuditStream', function() {
 
 });
 
+describe('AuditStream#fromRecords', function() {
+
+  it('should return the same result when created from record', function(done) {
+    var audit1 = new AuditStream(12);
+    audit1.on('finish', function() {
+      var tree1 = audit1.getPublicRecord();
+      var challenges1 = audit1.getPrivateRecord().challenges;
+      var audit2 = AuditStream.fromRecords(challenges1, tree1);
+      var tree2 = audit2.getPublicRecord();
+      var challenges2 = audit2.getPrivateRecord().challenges;
+      challenges2.forEach(function(c, i) {
+        expect(c).to.equal(challenges1[i]);
+      });
+      tree2.forEach(function(l, i) {
+        expect(l).to.equal(tree1[i]);
+      });
+      expect(
+        audit1.getPrivateRecord().depth
+      ).to.equal(
+        audit2.getPrivateRecord().depth
+      );
+      expect(
+        audit1.getPrivateRecord().root
+      ).to.equal(
+        audit2.getPrivateRecord().root
+      );
+      done();
+    });
+    audit1.write(SHARD);
+    audit1.end();
+  });
+
+});
+
 describe('Audit+AuditStream/Compatibility', function() {
 
   it('should return the same structures given the same input', function(done) {