Fixed concurrency issues in cur & tran managers

Closes #38

Author: ilyalukyanov

src/LightningDB/Factories/CursorManager.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
@@ -9,17 +10,16 @@ namespace LightningDB.Factories
     class CursorManager
     {
         private readonly LightningTransaction _transaction;
-
-        private readonly HashSet<IntPtr> _cursors;
-
+        private readonly ConcurrentDictionary<IntPtr, bool> _cursors;
+        
         public CursorManager(LightningTransaction transaction)
         {
             if (transaction == null)
                 throw new ArgumentNullException("transaction");
 
             _transaction = transaction;
 
-            _cursors = new HashSet<IntPtr>();
+            _cursors = new ConcurrentDictionary<IntPtr, bool>();
         }
 
         private IntPtr CreateCursorHandle(uint dbHandle)
@@ -38,7 +38,7 @@ private void CloseCursor(IntPtr cursorHandle)
         public LightningCursor OpenCursor(LightningDatabase db)
         {
             var handle = CreateCursorHandle(db._handle);
-            _cursors.Add(handle);
+            _cursors.TryAdd(handle, true);
 
             return new LightningCursor(db, _transaction, handle);
         }
@@ -51,14 +51,15 @@ public void CloseCursor(LightningCursor cursor)
             }
             finally
             {
-                _cursors.Remove(cursor._handle);
+                bool value;
+                _cursors.TryRemove(cursor._handle, out value);
             }
         }
 
         public void CloseAll()
         {
-            foreach (var handle in _cursors)
-                CloseCursor(handle);
+            foreach (var p in _cursors)
+                CloseCursor(p.Key);
 
             _cursors.Clear();
         }

src/LightningDB/Factories/TransactionManager.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Concurrent;
 using System.Collections.Generic;
 using System.Linq;
 using System.Text;
@@ -12,7 +13,7 @@ class TransactionManager
         private readonly LightningTransaction _parentTransaction;
         private readonly IntPtr _parentHandle;
 
-        private readonly HashSet<LightningTransaction> _transactions;
+        private readonly ConcurrentDictionary<LightningTransaction, bool> _transactions;
 
         public TransactionManager(LightningEnvironment environment, LightningTransaction parentTransaction)
         {
@@ -26,7 +27,7 @@ public TransactionManager(LightningEnvironment environment, LightningTransaction
                 ? parentTransaction._handle
                 : IntPtr.Zero;
 
-            _transactions = new HashSet<LightningTransaction>();
+            _transactions = new ConcurrentDictionary<LightningTransaction, bool>();
         }
 
         private void EnsureEnvironmentOpened()
@@ -44,23 +45,24 @@ public LightningTransaction Create(TransactionBeginFlags beginFlags)
 
             var tran = new LightningTransaction(_environment, handle, _parentTransaction, beginFlags);
 
-            _transactions.Add(tran);
+            _transactions.TryAdd(tran, true);
 
             return tran;
         }
 
         public void WasDiscarded(LightningTransaction tn)
         {
-            _transactions.Remove(tn);
+            bool value;
+            _transactions.TryRemove(tn, out value);
         }
 
         private static void AbortAll(TransactionManager manager)
         {
 
-            foreach (var tn in manager._transactions.ToList())
+            foreach (var p in manager._transactions.ToList())
             {
-                AbortAll(tn.SubTransactionsManager);
-                tn.Abort();
+                AbortAll(p.Key.SubTransactionsManager);
+                p.Key.Abort();
             }
         }