/Spss/SpssSafeHandle.cs

//-----------------------------------------------------------------------

// <copyright file="SpssSafeHandle.cs" company="Andrew Arnott">

//     Copyright (c) Andrew Arnott. All rights reserved.

//     Copyright (c) Brigham Young University

// </copyright>

//-----------------------------------------------------------------------



namespace Spss {

	using System;

	using Microsoft.Win32.SafeHandles;



	public class SpssSafeHandle : SafeHandleMinusOneIsInvalid {

		private SpssFileAccess accessMode;



		/// <summary>

		/// Initializes a new instance of the <see cref="SpssSafeHandle"/> class.

		/// </summary>

		/// <param name="handle">The SPSS handle.</param>

		/// <param name="accessMode">The access mode the handle was opened with.</param>

		public SpssSafeHandle(int handle, SpssFileAccess accessMode) : base(true) {

			this.accessMode = accessMode;

			this.SetHandle(new IntPtr(handle));

		}



		public static implicit operator int(SpssSafeHandle handle) {

			if (handle.IsInvalid) {

				throw new InvalidOperationException("Invalid SPSS handle.");

			}



			if (handle.IsClosed) {

				throw new InvalidOperationException("SPSS handle has been closed.");

			}



			return handle.handle.ToInt32();

		}



		/// <summary>

		/// When overridden in a derived class, executes the code required to free the handle.

		/// </summary>

		/// <returns>

		/// true if the handle is released successfully; otherwise, in the event of a catastrophic failure, false. In this case, it generates a releaseHandleFailed MDA Managed Debugging Assistant.

		/// </returns>

		protected override bool ReleaseHandle() {

			switch (this.accessMode) {

				case SpssFileAccess.Read:

					ReturnCode result = SpssSafeWrapper.spssCloseReadImpl(handle.ToInt32());

					return result == ReturnCode.SPSS_OK;

				case SpssFileAccess.Append:

					result = SpssSafeWrapper.spssCloseAppendImpl(handle.ToInt32());

					return result == ReturnCode.SPSS_OK;

				case SpssFileAccess.Create:

					result = SpssSafeWrapper.spssCloseWriteImpl(handle.ToInt32());

					return result == ReturnCode.SPSS_OK || result == ReturnCode.SPSS_DICT_NOTCOMMIT;

				default:

					return false;

			}

		}

	}

}