SafeMILHandleMemoryPressure.cs source code in C# .NET

Source code for the .NET framework in C#

                        
Code:

                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / Core / CSharp / System / Windows / Media / SafeMILHandleMemoryPressure.cs / 1407647 / SafeMILHandleMemoryPressure.cs
                        

                        
                            //---------------------------------------------------------------------------- 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
// 
// Description: 
//      Tracks the amount of native memory used by SafeMILHandle objects.
//--------------------------------------------------------------------------- 

using System;
using System.Security;
using MS.Internal; 
using System.Threading;
 
namespace System.Windows.Media 
{
    internal class SafeMILHandleMemoryPressure 
    {
        /// 
        ///    Critical: This code calls into AddMemoryPressure which has a link demand.
        ///  
        [SecurityCritical]
        internal SafeMILHandleMemoryPressure(long gcPressure) 
        { 
            _gcPressure = gcPressure;
            _refCount = 0; 

            if (_gcPressure > SMALL_BITMAP_MEM)
            {
                MemoryPressure.Add(_gcPressure); 
            }
            else 
            { 
                GC.AddMemoryPressure(_gcPressure);
            } 
        }

        internal void AddRef()
        { 
            Interlocked.Increment(ref _refCount);
        } 
 
        /// 
        ///    Critical: This code calls into RemoveMemoryPressure which has a link demand. 
        /// 
        [SecurityCritical]
        internal void Release()
        { 
            if (Interlocked.Decrement(ref _refCount) == 0)
            { 
                if (_gcPressure > SMALL_BITMAP_MEM) 
                {
                    MemoryPressure.Remove(_gcPressure); 
                }
                else
                {
                    GC.RemoveMemoryPressure(_gcPressure); 
                }
 
                _gcPressure = 0; 
            }
        } 

        // Estimated size in bytes of the unmanaged memory
        private long _gcPressure;
 
        //
        // SafeMILHandleMemoryPressure does its own ref counting in managed code, because the 
        // associated memory pressure should be removed when there are no more managed 
        // references to the unmanaged resource. There can still be references to it from
        // unmanaged code elsewhere, but that should not prevent the memory pressure from being 
        // released.
        //
        private int _refCount;
 
        //
        // The memory usage for a "small" bitmap 
        // 
        // Small bitmaps will be handled by GC.AddMemoryPressure() rather than WPF's own
        // MemoryPressure algorithm. GC's algorithm is less aggressive than WPF's, and will 
        // result in fewer expensive GC.Collect(2) operations.
        //
        // For now, a small bitmap is 32x32 or less. It's at 4 bytes per pixel, and the *2 is
        // to account for the doubled estimate in 
        //     BitmapSourceMILSafeHandle.ComputeEstimatedSize().
        // 
        private const long SMALL_BITMAP_MEM = 32 * 32 * 4 * 2; 
    }
} 


// File provided for Reference Use Only by Microsoft Corporation (c) 2007.
// Copyright (c) Microsoft Corporation. All rights reserved.

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