// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
 
using System;
using System.Diagnostics;
using System.Runtime.InteropServices;
using Roslyn.Utilities;
 
namespace Microsoft.CodeAnalysis.Shared.Extensions
{
    internal static class SafeHandleExtensions
    {
        /// <summary>
        /// Acquires a lease on a safe handle. The lease increments the reference count of the <see cref="SafeHandle"/>
        /// to ensure the handle is not released prior to the lease being released.
        /// </summary>
        /// <remarks>
        /// This method is intended to be used in the initializer of a <c>using</c> statement. Failing to release the
        /// lease will permanently prevent the underlying <see cref="SafeHandle"/> from being released by the garbage
        /// collector.
        /// </remarks>
        /// <param name="handle">The <see cref="SafeHandle"/> to lease.</param>
        /// <returns>A <see cref="SafeHandleLease"/>, which must be disposed to release the resource.</returns>
        /// <exception cref="ObjectDisposedException">If the lease could not be acquired.</exception>
        public static SafeHandleLease Lease(this SafeHandle handle)
        {
            RoslynDebug.AssertNotNull(handle);
 
            var success = false;
            try
            {
                handle.DangerousAddRef(ref success);
                Debug.Assert(success, $"{nameof(SafeHandle.DangerousAddRef)} does not return when {nameof(success)} is false.");
 
                return new SafeHandleLease(handle);
            }
            catch
            {
                if (success)
                    handle.DangerousRelease();
 
                throw;
            }
        }
    }
}