//------------------------------------------------------------------------------
// <copyright file="OdbcEnvironment.cs" company="Microsoft">
//      Copyright (c) Microsoft Corporation.  All rights reserved.
// </copyright>
// <owner current="true" primary="true">Microsoft</owner>
// <owner current="true" primary="false">Microsoft</owner>
//------------------------------------------------------------------------------

using System;
using System.Data;
using System.Data.Common;
using System.Threading;


namespace System.Data.Odbc {
    sealed internal class OdbcEnvironment {
        static private object _globalEnvironmentHandle;
        static private object _globalEnvironmentHandleLock = new object();

        private OdbcEnvironment () {}  // default const.
        
        static internal OdbcEnvironmentHandle GetGlobalEnvironmentHandle() {
            OdbcEnvironmentHandle globalEnvironmentHandle = _globalEnvironmentHandle as OdbcEnvironmentHandle;
            if(null == globalEnvironmentHandle) {
                ADP.CheckVersionMDAC(true);
                
                lock(_globalEnvironmentHandleLock) {
                    globalEnvironmentHandle = _globalEnvironmentHandle as OdbcEnvironmentHandle;
                    if(null == globalEnvironmentHandle) {
                        globalEnvironmentHandle = new OdbcEnvironmentHandle();
                        _globalEnvironmentHandle = globalEnvironmentHandle;
                    }
                }
            }
            return globalEnvironmentHandle;
        }

        static internal void ReleaseObjectPool() {
            object globalEnvironmentHandle = Interlocked.Exchange(ref _globalEnvironmentHandle, null);
            if(null != globalEnvironmentHandle) {
                (globalEnvironmentHandle as OdbcEnvironmentHandle).Dispose(); // internally refcounted so will happen correctly
            }
        }
    }
}