add chain scanner.

lib/bcoin/chaindb.js

@@ -1131,6 +1131,65 @@ ChainDB.prototype.getCoins = function getCoins(hash, callback) {
   }, callback);
 };
 
+/**
+ * Scan the blockchain for transactions containing specified address hashes.
+ * @param {Hash} start - Block hash to start at.
+ * @param {Hash[]} hashes - Address hashes.
+ * @param {Function} iter - Iterator. Accepts ({@link TX}, {@link Function}).
+ * @param {Function} callback
+ */
+
+ChainDB.prototype.scan = function scan(start, hashes, iter, callback) {
+  var self = this;
+  var hashMap = {};
+  var total = 0;
+  var i;
+
+  if (!start)
+    start = this.network.genesis.hash;
+
+  for (i = 0; i < hashes.length; i++)
+    hashMap[hashes[i]] = true;
+
+  this.logger.info('Rescanning from block %s.', utils.revHex(start));
+
+  (function next(err, hash) {
+    if (err)
+      return callback(err);
+
+    if (!hash) {
+      self.logger.info('Finished scanning %d blocks.', total);
+      return callback();
+    }
+
+    total++;
+
+    self.getFullBlock(hash, function(err, block) {
+      if (err)
+        return next(err);
+
+      self.logger.info('Scanning block %s.', utils.revHex(hash));
+
+      utils.forEachSerial(block.txs, function(tx, next) {
+        var hashes = tx.getHashes('hex');
+        var i, hash;
+
+        for (i = 0; i < hashes.length; i++) {
+          hash = hashes[i];
+          if (hashMap[hash])
+            return iter(tx, next);
+        }
+
+        next();
+      }, function(err) {
+        if (err)
+          return next(err);
+        self.getNextHash(hash, next);
+      });
+    });
+  })(null, start);
+};
+
 /**
  * Retrieve a transaction (not filled with coins).
  * @param {Hash} hash