Code:
/ DotNET / DotNET / 8.0 / untmp / whidbey / REDBITS / ndp / clr / src / BCL / System / Runtime / InteropServices / GcHandle.cs / 1 / GcHandle.cs
// ==++== // // Copyright (c) Microsoft Corporation. All rights reserved. // // ==--== namespace System.Runtime.InteropServices { using System; using System.Security.Permissions; using System.Runtime.CompilerServices; using System.Threading; // These are the types of handles used by the EE. IMPORTANT: These must // match the definitions in ObjectHandle.h in the EE. [Serializable] [System.Runtime.InteropServices.ComVisible(true)] public enum GCHandleType { Weak = 0, WeakTrackResurrection = 1, Normal = 2, Pinned = 3 } // This class allows you to create an opaque, GC handle to any // COM+ object. A GC handle is used when an object reference must be // reachable from unmanaged memory. There are 3 kinds of roots: // Normal - keeps the object from being collected. // Weak - allows object to be collected and handle contents will be zeroed. // Weak references are zeroed before the finalizer runs, so if the // object is resurrected in the finalizer the weak reference is // still zeroed. // WeakTrackResurrection - Same as weak, but stays until after object is // really gone. // Pinned - same as normal, but allows the address of the actual object // to be taken. // [StructLayout(LayoutKind.Sequential)] [System.Runtime.InteropServices.ComVisible(true)] public struct GCHandle { internal static readonly IntPtr InvalidCookie = new IntPtr(unchecked((int)0xFFFFFFFF)); #if MDA_SUPPORTED static GCHandle() { s_probeIsActive = Mda.IsInvalidGCHandleCookieProbeEnabled(); if (s_probeIsActive) s_cookieTable = new GCHandleCookieTable(); } #endif // Allocate a handle storing the object and the type. internal GCHandle(Object value, GCHandleType type) { m_handle = InternalAlloc(value, type); // Record if the handle is pinned. if (type == GCHandleType.Pinned) SetIsPinned(); } // Used in the conversion functions below. internal GCHandle(IntPtr handle) { InternalCheckDomain(handle); m_handle = handle; } // Creates a new GC handle for an object. // // value - The object that the GC handle is created for. // type - The type of GC handle to create. // // returns a new GC handle that protects the object. [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.UnmanagedCode)] public static GCHandle Alloc(Object value) { return new GCHandle(value, GCHandleType.Normal); } [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.UnmanagedCode)] public static GCHandle Alloc(Object value, GCHandleType type) { return new GCHandle(value, type); } // Frees a GC handle. [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.UnmanagedCode)] public void Free() { // Copy the handle instance member to a local variable. This is required to prevent // race conditions releasing the handle. IntPtr handle = m_handle; // Free the handle if it hasn't already been freed. if (handle != IntPtr.Zero && Interlocked.CompareExchange(ref m_handle, IntPtr.Zero, handle) == handle) { #if WIN32 InternalFree((IntPtr)(((int)handle) & ~1)); #else InternalFree((IntPtr)(((long)handle) & ~1L)); #endif #if MDA_SUPPORTED // If this handle was passed out to unmanaged code, we need to remove it // from the cookie table. if (s_probeIsActive) s_cookieTable.RemoveHandleIfPresent(handle); #endif } else { throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_HandleIsNotInitialized")); } } // Target property - allows getting / updating of the handle's referent. public Object Target { [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.UnmanagedCode)] get { // Check if the handle was never initialized or was freed. if (m_handle == IntPtr.Zero) throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_HandleIsNotInitialized")); return InternalGet(GetHandleValue()); } [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.UnmanagedCode)] set { // Check if the handle was never initialized or was freed. if (m_handle == IntPtr.Zero) throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_HandleIsNotInitialized")); InternalSet(GetHandleValue(), value, IsPinned()); } } // Retrieve the address of an object in a Pinned handle. This throws // an exception if the handle is any type other than Pinned. [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.UnmanagedCode)] public IntPtr AddrOfPinnedObject() { // Check if the handle was not a pinned handle. if (!IsPinned()) { // Check if the handle was never initialized for was freed. if (m_handle == IntPtr.Zero) throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_HandleIsNotInitialized")); // You can only get the address of pinned handles. throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_HandleIsNotPinned")); } // Get the address. return InternalAddrOfPinnedObject(GetHandleValue()); } // Determine whether this handle has been allocated or not. public bool IsAllocated { get { return m_handle != IntPtr.Zero; } } // Used to create a GCHandle from an int. This is intended to // be used with the reverse conversion. [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.UnmanagedCode)] public static explicit operator GCHandle(IntPtr value) { return FromIntPtr(value); } [SecurityPermissionAttribute(SecurityAction.LinkDemand, Flags=SecurityPermissionFlag.UnmanagedCode)] public static GCHandle FromIntPtr(IntPtr value) { if (value == IntPtr.Zero) throw new InvalidOperationException(Environment.GetResourceString("InvalidOperation_HandleIsNotInitialized")); IntPtr handle = value; #if MDA_SUPPORTED if (s_probeIsActive) { // Make sure this cookie matches up with a GCHandle we've passed out a cookie for. handle = s_cookieTable.GetHandle(value); if (IntPtr.Zero == handle) { // Fire an MDA if we were unable to retrieve the GCHandle. Mda.FireInvalidGCHandleCookieProbe(value); return new GCHandle(IntPtr.Zero); } } #endif return new GCHandle(handle); } // Used to get the internal integer representation of the handle out. public static explicit operator IntPtr(GCHandle value) { return ToIntPtr(value); } public static IntPtr ToIntPtr(GCHandle value) { #if MDA_SUPPORTED if (s_probeIsActive) { // Remember that we passed this GCHandle out by storing the cookie we returned so we // can later validate. return s_cookieTable.FindOrAddHandle(value.m_handle); } #endif return value.m_handle; } public override int GetHashCode() { return (int)m_handle; } public override bool Equals(Object o) { GCHandle hnd; // Check that o is a GCHandle first if(o == null || !(o is GCHandle)) return false; else hnd = (GCHandle) o; return m_handle == hnd.m_handle; } public static bool operator ==(GCHandle a, GCHandle b) { return a.m_handle == b.m_handle; } public static bool operator !=(GCHandle a, GCHandle b) { return a.m_handle != b.m_handle; } internal IntPtr GetHandleValue() { #if WIN32 return new IntPtr(((int)m_handle) & ~1); #else return new IntPtr(((long)m_handle) & ~1L); #endif } internal bool IsPinned() { #if WIN32 return (((int)m_handle) & 1) != 0; #else return (((long)m_handle) & 1) != 0; #endif } internal void SetIsPinned() { #if WIN32 m_handle = new IntPtr(((int)m_handle) | 1); #else m_handle = new IntPtr(((long)m_handle) | 1L); #endif } // Internal native calls that this implementation uses. [MethodImplAttribute(MethodImplOptions.InternalCall)] internal static extern IntPtr InternalAlloc(Object value, GCHandleType type); [MethodImplAttribute(MethodImplOptions.InternalCall)] internal static extern void InternalFree(IntPtr handle); [MethodImplAttribute(MethodImplOptions.InternalCall)] internal static extern Object InternalGet(IntPtr handle); [MethodImplAttribute(MethodImplOptions.InternalCall)] internal static extern void InternalSet(IntPtr handle, Object value, bool isPinned); [MethodImplAttribute(MethodImplOptions.InternalCall)] internal static extern Object InternalCompareExchange(IntPtr handle, Object value, Object oldValue, bool isPinned); [MethodImplAttribute(MethodImplOptions.InternalCall)] internal static extern IntPtr InternalAddrOfPinnedObject(IntPtr handle); [MethodImplAttribute(MethodImplOptions.InternalCall)] internal static extern void InternalCheckDomain(IntPtr handle); // The actual integer handle value that the EE uses internally. private IntPtr m_handle; #if MDA_SUPPORTED // The GCHandle cookie table. static private GCHandleCookieTable s_cookieTable = null; static private bool s_probeIsActive = false; #endif } }
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