/DLR_Main/Runtime/Microsoft.Dynamic/ComInterop/ExcepInfo.cs

/* ****************************************************************************

 *

 * Copyright (c) Microsoft Corporation. 

 *

 * This source code is subject to terms and conditions of the Apache License, Version 2.0. A 

 * copy of the license can be found in the License.html file at the root of this distribution. If 

 * you cannot locate the  Apache License, Version 2.0, please send an email to 

 * dlr@microsoft.com. By using this source code in any fashion, you are agreeing to be bound 

 * by the terms of the Apache License, Version 2.0.

 *

 * You must not remove this notice, or any other, from this software.

 *

 *

 * ***************************************************************************/



#if !SILVERLIGHT // ComObject



using System;

using System.Diagnostics;

using System.Reflection;

using System.Runtime.InteropServices;

using System.Security;

using ComTypes = System.Runtime.InteropServices.ComTypes;



namespace Microsoft.Scripting.ComInterop {

    /// <summary>

    /// This is similar to ComTypes.EXCEPINFO, but lets us do our own custom marshaling

    /// </summary>

    [StructLayout(LayoutKind.Sequential)]

    internal struct ExcepInfo {

        private short wCode;

        private short wReserved;

        private IntPtr bstrSource;

        private IntPtr bstrDescription;

        private IntPtr bstrHelpFile;

        private int dwHelpContext;

        private IntPtr pvReserved;

        private IntPtr pfnDeferredFillIn;

        private int scode;



#if DEBUG

        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2207:InitializeValueTypeStaticFieldsInline")]

        static ExcepInfo() {

            Debug.Assert(Marshal.SizeOf(typeof(ExcepInfo)) == Marshal.SizeOf(typeof(ComTypes.EXCEPINFO)));

        }

#endif



        private static string ConvertAndFreeBstr(ref IntPtr bstr) {

            if (bstr == IntPtr.Zero) {

                return null;

            }



            string result = Marshal.PtrToStringBSTR(bstr);

            Marshal.FreeBSTR(bstr);

            bstr = IntPtr.Zero;

            return result;

        }



        internal void Dummy() {

            wCode = 0;

            wReserved = 0; wReserved++;

            bstrSource = IntPtr.Zero;

            bstrDescription = IntPtr.Zero;

            bstrHelpFile = IntPtr.Zero;

            dwHelpContext = 0;

            pfnDeferredFillIn = IntPtr.Zero;

            pvReserved = IntPtr.Zero;

            scode = 0;



            throw Error.MethodShouldNotBeCalled();

        }



        [System.Diagnostics.CodeAnalysis.SuppressMessage("Microsoft.Usage", "CA2201:DoNotRaiseReservedExceptionTypes")]

        internal Exception GetException() {

            Debug.Assert(pfnDeferredFillIn == IntPtr.Zero);

#if DEBUG

            System.Diagnostics.Debug.Assert(wReserved != -1);

            wReserved = -1; // to ensure that the method gets called only once

#endif



            int errorCode = (scode != 0) ? scode : wCode;

            Exception exception = Marshal.GetExceptionForHR(errorCode);



            string message = ConvertAndFreeBstr(ref bstrDescription);

            if (message != null) {

                // If we have a custom message, create a new Exception object with the message set correctly.

                // We need to create a new object because "exception.Message" is a read-only property.

                if (exception is COMException) {

                    exception = new COMException(message, errorCode);

                } else {

                    Type exceptionType = exception.GetType();

                    ConstructorInfo ctor = exceptionType.GetConstructor(new Type[] { typeof(string) });

                    if (ctor != null) {

                        exception = (Exception)ctor.Invoke(new object[] { message });

                    }

                }

            }



            exception.Source = ConvertAndFreeBstr(ref bstrSource);



            string helpLink = ConvertAndFreeBstr(ref bstrHelpFile);

            if (helpLink != null && dwHelpContext != 0) {

                helpLink += "#" + dwHelpContext;

            }

            exception.HelpLink = helpLink;



            return exception;

        }

    }

}



#endif