Added extensions w/o db param using default db opened automatically

Default Encoding and DatabaseOpenFlags added to global config. Some
additional refactoring

Author: ilyalukyanov

src/LightningDB/DatabaseOpenFlags.cs

@@ -12,7 +12,7 @@ public enum DatabaseOpenFlags
         /// No special options.
         /// </summary>
         None = 0,
-
+                
         /// <summary>
         /// MDB_REVERSEKEY. Keys are strings to be compared in reverse order, from the end of the strings to the beginning. By default, Keys are treated as strings and compared from beginning to end.
         /// </summary>

src/LightningDB/LightningConfig.cs

@@ -59,5 +59,36 @@ static Environment()
             /// </summary>
             public static bool AutoReduceMapSizeIn32BitProcess { get; set; }
         }
+
+        /// <summary>
+        /// Basic environment conviguration
+        /// </summary>
+        public static class Database
+        {
+            private static Encoding _defaultEncoding;
+
+            static Database()
+            {
+                DefaultOpenFlags = DatabaseOpenFlags.None;
+                DefaultEncoding = Encoding.UTF8;
+            }
+
+            /// <summary>
+            /// Default database open flags
+            /// </summary>
+            public static DatabaseOpenFlags DefaultOpenFlags { get; set; }
+
+            public static Encoding DefaultEncoding
+            {
+                get { return _defaultEncoding; }
+                set
+                {
+                    if (value == null)
+                        throw new ArgumentNullException("value");
+
+                    _defaultEncoding = value;
+                }
+            }
+        }
     }
 }

src/LightningDB/LightningDatabase.cs

@@ -19,31 +19,25 @@ public class LightningDatabase : IDisposable
         private readonly string _name;
         private bool _shouldDispose;
 
-        /// <summary>
-        /// Creates a LightningDatabase instance.
-        /// </summary>
-        /// <param name="name">Database name.</param>
-        /// <param name="flags">Database open flags.</param>
-        /// <param name="tran">Active transaction.</param>
-        public LightningDatabase(string name, DatabaseOpenFlags flags, LightningTransaction tran)
-            : this (name, flags, tran, Encoding.UTF8)
-        {
-        }
-
         /// <summary>
         /// Creates a LightningDatabase instance.
         /// </summary>
         /// <param name="name">Database name.</param>
         /// <param name="flags">Database open flags/</param>
         /// <param name="tran">Active transaction.</param>
         /// <param name="encoding">Default strings encoding.</param>
-        public LightningDatabase(string name, DatabaseOpenFlags flags, LightningTransaction tran, Encoding encoding)
+        public LightningDatabase(string name, LightningTransaction tran, DatabaseOpenFlags? flags, Encoding encoding = null)
         {
             if (tran == null)
                 throw new ArgumentNullException("tran");
 
+            if (!flags.HasValue)
+                flags = LightningConfig.Database.DefaultOpenFlags;
+
+            encoding = encoding ?? LightningConfig.Database.DefaultEncoding;
+
             UInt32 handle = default(UInt32);
-            NativeMethods.Execute(lib => lib.mdb_dbi_open(tran._handle, name, flags, out handle));
+            NativeMethods.Execute(lib => lib.mdb_dbi_open(tran._handle, name, flags.Value, out handle));
 
             _name = name ?? DefaultDatabaseName;
 
@@ -52,10 +46,12 @@ public LightningDatabase(string name, DatabaseOpenFlags flags, LightningTransact
 
             this.IsOpened = true;
             this.Encoding = encoding;
-            this.OpenFlags = flags;
+            this.OpenFlags = flags.Value;
             this.Environment = tran.Environment;
         }
 
+        internal bool IsReleased { get { return !_shouldDispose; } }
+
         /// <summary>
         /// Is database opened.
         /// </summary>

src/LightningDB/LightningEnvironment.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Concurrent;
 using System.Collections.Generic;
+using System.Text;
 using LightningDB.Converters;
 using LightningDB.Native;
 
@@ -272,20 +273,23 @@ internal void ReleaseDatabase(LightningDatabase db)
         }
 
         //TODO: Upgrade db flags?
-        internal LightningDatabase OpenDatabase(string name, DatabaseOpenFlags flags, LightningTransaction tran)
+        internal LightningDatabase OpenDatabase(string name, LightningTransaction tran, DatabaseOpenFlags? flags, Encoding encoding)
         {
             var internalName = name ?? LightningDatabase.DefaultDatabaseName;
             var db = _openedDatabases.GetOrAdd(internalName, n => 
             {
-                var ldb = new LightningDatabase(name, flags, tran);
+                var ldb = new LightningDatabase(name, tran, flags, encoding);
                 _databasesForReuse.Add(ldb._handle);
 
                 return ldb;
             });
 
-            if (db.OpenFlags != flags)
+            if (db.OpenFlags != flags.GetValueOrDefault())
                 throw new InvalidOperationException("Database " + internalName + " already opened with different flags");
 
+            if (db.Encoding != (encoding ?? LightningConfig.Database.DefaultEncoding))
+                throw new InvalidOperationException("Can not change encoding of already opened database");
+
             return db;
         }
 

src/LightningDB/LightningTransaction.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Text;
 using LightningDB.Native;
 
 namespace LightningDB
@@ -15,6 +16,8 @@ public class LightningTransaction : IClosingEventSource, IDisposable
 
         internal IntPtr _handle;
 
+        private LightningDatabase _defaultDatabase;
+
         /// <summary>
         /// Created new instance of LightningTransaction
         /// </summary>
@@ -102,10 +105,22 @@ public LightningTransaction BeginTransaction()
         /// </summary>
         /// <param name="name">Database name (optional). If null then the default name is used.</param>
         /// <param name="flags">Database open options (optionsl).</param>
+        /// <param name="encoding">Database keys encoding.</param>
         /// <returns>Created database wrapper.</returns>
-        public LightningDatabase OpenDatabase(string name = null, DatabaseOpenFlags flags = DatabaseOpenFlags.None)
+        public LightningDatabase OpenDatabase(string name = null, DatabaseOpenFlags? flags = null, Encoding encoding = null)
         {
-            return this.Environment.OpenDatabase(name, flags, this);
+            if (name == null && (!flags.HasValue || flags.Value == LightningConfig.Database.DefaultOpenFlags))
+            {                
+                if (_defaultDatabase == null || _defaultDatabase.IsReleased)
+                    _defaultDatabase = this.Environment.OpenDatabase(name, this, flags, encoding);
+
+                if (_defaultDatabase.Encoding != (encoding ?? LightningConfig.Database.DefaultEncoding))
+                    throw new InvalidOperationException("Can not change encoding of already opened database");
+
+                return _defaultDatabase;
+            }
+
+            return this.Environment.OpenDatabase(name, this, flags, encoding);
         }
 
         /// <summary>