微软.net精简框架常见问题及回答(中文版)(60)
Public Function OpenMySubKey() As Long
Dim hkey As IntPtr = IntPtr.Zero
Return RegOpenKey(HKEY_CLASSES_ROOT, "MySubKey", hkey)
End Function 'OpenMySubKey
6.14. 如何把 byte[] 转换成 IntPtr?
有不止一种的方法访问IntPtr。
第一种方法，使用非安全代码，直接用指针指向byte数组。 //C#
unsafe
{
byte[] test = new byte[5];
fixed (byte* p = &test[0])
{
*p = 0xff;
}
}
也可以使用GCHandle指向对象。 //C#
using System.Runtime.InteropServices;
byte[] test = new byte[5];
GCHandle hObject = GCHandle.Alloc(test, GCHandleType.Pinned);
IntPtr pObject = hObject.AddrOfPinnedObject();
if(hObject.IsAllocated)
hObject.Free();
'VB
Imports System.Runtime.InteropServices
Dim test(4) As Byte
Dim hObject As GCHandle = GCHandle.Alloc(test, GCHandleType.Pinned)
Dim pObject As IntPtr = hObject.AddrOfPinnedObject()
If hObject.IsAllocated Then
hObject.Free()
End If
最后，可以使用LocalAlloc和Marshalling函数复制内存块得到数据块。
//C#
[DllImport("coredll.dll",SetLastError=true)]
public static extern IntPtr LocalAlloc(uint uFlags, uint uBytes);
[DllImport("coredll.dll",SetLastError=true)]
public static extern IntPtr LocalFree(IntPtr hMem);
[DllImport("coredll.dll",SetLastError=true)]
public static extern IntPtr LocalReAlloc(IntPtr hMem, uint uBytes, uint fuFlags);
public const uint LMEM_FIXED = 0;
public const uint LMEM_MOVEABLE = 2;
public const uint LMEM_ZEROINIT = 0x0040;
byte[] test = new byte[5];
IntPtr p = LocalAlloc(LMEM_FIXED | LMEM_ZEROINIT, (uint)test.Length);
if (p == IntPtr.Zero)
{
throw new OutOfMemoryException();
}
else
{
Marshal.Copy(test, 0, p, test.Length);
}
'VB
<DllImport("coredll.dll", SetLastError:=True)> _
Public Shared Function LocalAlloc(ByVal uFlags As UInt32, ByVal uBytes As UInt32) As IntPtr
End Function
<DllImport("coredll.dll", SetLastError:=True)> _
Public Shared Function LocalFree(ByVal hMem As IntPtr) As IntPtr
End Function
<DllImport("coredll.dll", SetLastError:=True)> _
Public Shared Function LocalReAlloc(ByVal hMem As IntPtr, ByVal uBytes As UInt32, ByVal fuFlags As UInt32) As IntPtr
End Function
Public Const LMEM_FIXED As Integer = 0
Public Const LMEM_MOVEABLE As Integer = 2
Public Const LMEM_ZEROINIT As Integer = &H40
Dim test(4) As Byte
Dim p As IntPtr = LocalAlloc(Convert.ToUInt32(LMEM_FIXED Or LMEM_ZEROINIT), Convert.ToUInt32(test.Length))
If p.Equals(IntPtr.Zero) Then
Throw New OutOfMemoryException
Else
Marshal.Copy(test, 0, p, test.Length)
End If