CommonRemoteMemoryBlock.cs source code in C# .NET

                        Code:
                         / 4.0 / 4.0 / untmp / DEVDIV_TFS / Dev10 / Releases / RTMRel / wpf / src / UIAutomation / Win32Providers / MS / Internal / AutomationProxies / CommonRemoteMemoryBlock.cs / 1305600 / CommonRemoteMemoryBlock.cs
                        
                        
                            //---------------------------------------------------------------------------- 
//
// 
//    Copyright (C) Microsoft Corporation.  All rights reserved.
//  
//
// Description: 
//      Module to allocate shared memory between process. 
//      The memory allocation scheme is different for Win 9x and WinNT
//      Performance measurements showed that using a global heap mechanism 
//      is fastest on Win 9x.
//
//      When the dll is loaded, a counter is set to 1. For each instance
//      creation/destruction, the counter is is incremented/decremented. 
//      When the dll is released, the counter gets to zero and the static
//      heap on Win 9x is destroyed. 
// 
// History:
//  07/01/2003 : a-jeanp    Created 
//---------------------------------------------------------------------------

using System;
using System.ComponentModel; 
using System.Security;
using System.Security.Permissions; 
using System.Runtime.InteropServices; 
using System.Runtime.CompilerServices;
using System.Windows.Automation; 
using Microsoft.Win32.SafeHandles;
using MS.Win32;

namespace MS.Internal.AutomationProxies 
{
    // Class to allocate shared memory between process. 
    class RemoteMemoryBlock : SafeHandleZeroOrMinusOneIsInvalid 
    {
        // ----------------------------------------------------- 
        //
        // Constructors
        //
        // ----------------------------------------------------- 

        #region Constructors 
 
        // This constructor is used by the P/Invoke marshaling layer
        // to allocate a SafeHandle instance.  P/Invoke then does the 
        // appropriate method call, storing the handle in this class.
        private RemoteMemoryBlock() : base(true) {}

        internal RemoteMemoryBlock(int cbSize, SafeProcessHandle processHandle) : base(true) 
        {
            _processHandle = processHandle; 
 
            SetHandle(Misc.VirtualAllocEx(_processHandle, IntPtr.Zero, new UIntPtr((uint)cbSize), UnsafeNativeMethods.MEM_COMMIT, UnsafeNativeMethods.PAGE_READWRITE));
        } 

        // Uncomment this if & only if we need a constructor
        // that takes a handle from external code
        //internal RemoteMemoryBlock(IntPtr preexistingHandle, bool ownsHandle) : base(ownsHandle) 
        //{
        //    SetHandle(preexistingHandle); 
        //} 

        // 



        protected override bool ReleaseHandle() 
        {
            return Misc.VirtualFreeEx(_processHandle, handle, UIntPtr.Zero, UnsafeNativeMethods.MEM_RELEASE); 
        } 

        #endregion 

        // ------------------------------------------------------
        //
        // Internal Methods 
        //
        // ----------------------------------------------------- 
 
        #region Internal Methods
 
        internal IntPtr Address
        {
            get
            { 
                return handle;
            } 
        } 

        internal void WriteTo(IntPtr sourceAddress, IntPtr cbSize) 
        {
            int count;
            Misc.WriteProcessMemory(_processHandle, handle, sourceAddress, cbSize, out count);
        } 

        internal void ReadFrom(IntPtr remoteAddress, IntPtr destAddress, IntPtr cbSize) 
        { 
            int count;
            Misc.ReadProcessMemory(_processHandle, remoteAddress, destAddress, cbSize, out count); 
        }

        internal void ReadFrom(SafeCoTaskMem destAddress, IntPtr cbSize)
        { 
            int count;
            Misc.ReadProcessMemory(_processHandle, handle, destAddress, cbSize, out count); 
        } 
        internal void ReadFrom(IntPtr destAddress, IntPtr cbSize)
        { 
            int count;
            Misc.ReadProcessMemory(_processHandle, handle, destAddress, cbSize, out count);
        }
 
        // Helper function to handle common scenario of translating a remote
        // unmanaged char/wchar buffer in to a managed string object. 
        internal bool ReadString (out string str, int maxLength) 
        {
            // Clear the return string 
            str = null;

            // Ensure there is a buffer size
            if (0 >= maxLength) 
            {
                return false; 
            } 

            // Ensure proper allocation 
            using (SafeCoTaskMem ptr = new SafeCoTaskMem(maxLength))
            {
                if (ptr.IsInvalid)
                { 
                    return false;
                } 
                // Copy remote buffer back to local process... 
                ReadFrom(ptr, new IntPtr(maxLength * sizeof (char)));
 
                // Convert the local unmanaged buffer in to a string object
                str = ptr.GetStringUni(maxLength);

                // Note: lots of "old world" strings are null terminated 
                // Leaving the null termination in the System.String may lead
                // to some issues when used with the StringBuilder 
                int nullTermination = str.IndexOf('\0'); 

                if (-1 != nullTermination) 
                {
                    // We need to strip null terminated char and everything behind it from the str
                    str = str.Remove(nullTermination, maxLength - nullTermination);
                } 

                return true; 
            } 
        }
 
        #endregion

        // ------------------------------------------------------
        // 
        // Private Fields
        // 
        // ------------------------------------------------------ 

        #region Private Fields 

        private SafeProcessHandle _processHandle; // Handle of remote process

        #endregion 
    }
} 

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