Update with function for getOldestLockBlock

lib/local_comms.js

@@ -618,6 +618,38 @@ function Database(){
         });
     };
 
+    this.getOldestLockedBlock = function(){
+        /*
+        6-29-2017 - Snipa -
+        This function returns a decompressed block proto for the first locked block in the system as part of the
+        share depth functions.  DO NOT BLINDLY REPLACE getLastBlock WITH THIS FUNCTION.
+        */
+        this.refreshEnv();
+        debug("Getting the oldest locked block in the system");
+        let txn = this.env.beginTxn({readOnly: true});
+        let cursor = new this.lmdb.Cursor(txn, this.blockDB);
+        let highestBlock = null;
+        for (let found = cursor.goToFirst(); found; found = cursor.goToNext()) {
+            if (highestBlock !== null){
+                break;
+            }
+            cursor.getCurrentBinary(function(key, data){  // jshint ignore:line
+                let blockData = global.protos.Block.decode(data);
+                if (blockData.unlocked === false){
+                    highestBlock = blockData;
+                }
+            });
+        }
+        cursor.close();
+        txn.commit();
+        if (highestBlock !== null) {
+            debug("Got the oldest locked block in the system at height: " + highestBlock);
+        } else {
+            debug("There are no unlocked blocks in the system.  Woohoo!");
+        }
+        return highestBlock;
+    };
+
     this.cleanShareDBNew = function() {
         /*
          This function takes the difficulty of the current block, and the last PPS block.  If it's 0, save everything,