mcs/class/corlib/System.Runtime.InteropServices/GCHandle.cs

   1 //
   2 // System.Runtime.InteropServices/GCHandle.cs
   3 //
   4 // Authors:
   5 //   Ajay kumar Dwivedi (adwiv@yahoo.com) ??
   6 //   Paolo Molaro (lupus@ximian.com)
   7 //
   8
   9 using System;
  10 using System.Runtime.CompilerServices;
  11 using System.Runtime.InteropServices;
  12
  13 namespace System.Runtime.InteropServices
  14 {
  15         /// <summary>
  16         /// Summary description for GCHandle.
  17         /// </summary>
  18         public struct GCHandle
  19         {
  20                 // fields
  21                 private int handle;
  22
  23                 private GCHandle(IntPtr h)
  24                 {
  25                         handle = (int)h;
  26                 }
  27
  28                 // Constructors
  29                 private GCHandle(object obj)
  30                         : this(obj, GCHandleType.Normal)
  31                 {}
  32
  33                 private GCHandle(object value, GCHandleType type)
  34                 {
  35                         handle = GetTargetHandle (value, 0, type);
  36                 }
  37
  38                 // Properties
  39
  40                 public bool IsAllocated
  41                 {
  42                         get
  43                         {
  44                                 return (handle != 0);
  45                         }
  46                 }
  47
  48                 public object Target
  49                 {
  50                         get
  51                         {
  52                                 return GetTarget (handle);
  53                         }
  54                         set
  55                         {
  56                                 handle = GetTargetHandle (value, handle, (GCHandleType)(-1));
  57                         }
  58                 }
  59
  60                 // Methods
  61                 public IntPtr AddrOfPinnedObject()
  62                 {
  63                         IntPtr res = GetAddrOfPinnedObject(handle);
  64                         if (res == IntPtr.Zero)
  65                                 throw new InvalidOperationException("The handle is not of Pinned type");
  66                         return res;
  67                 }
  68
  69                 public static System.Runtime.InteropServices.GCHandle Alloc(object value)
  70                 {
  71                         return new GCHandle (value);
  72                 }
  73
  74                 public static System.Runtime.InteropServices.GCHandle Alloc(object value, GCHandleType type)
  75                 {
  76                         return new GCHandle (value,type);
  77                 }
  78
  79                 public void Free()
  80                 {
  81                         FreeHandle(handle);
  82                         handle = 0;
  83                 }
  84
  85                 public static explicit operator IntPtr (GCHandle value)
  86                 {
  87                         return (IntPtr) value.handle;
  88                 }
  89
  90                 public static explicit operator GCHandle(IntPtr value)
  91                 {
  92                         return new GCHandle (value);
  93                 }
  94
  95                 [MethodImplAttribute(MethodImplOptions.InternalCall)]
  96                 private extern static object GetTarget(int handle);
  97
  98                 [MethodImplAttribute(MethodImplOptions.InternalCall)]
  99                 private extern static int GetTargetHandle(object obj, int handle, GCHandleType type);
 100
 101                 [MethodImplAttribute(MethodImplOptions.InternalCall)]
 102                 private extern static void FreeHandle(int handle);
 103
 104                 [MethodImplAttribute(MethodImplOptions.InternalCall)]
 105                 private extern static IntPtr GetAddrOfPinnedObject(int handle);
 106         }
 107 }
 108