Marshal.AllocHGlobal

[Guest]

I have the following question

The Marshal class contains a function to allocate a block of memory
1. Marshal.AllocHGlobal ( int cb
2. Marshal.AllocHGlobal ( IntPtr cb

The first version I can understand, because the integer indicates the size of the memory block that is required
But the second version I do not understand. If I want a memoryblock of 20 bytes could I use

IntPtr p = Marshal.AllocHGlobal ( new IntPtr ( 20 ) )

Another reason for asking is the function Marshal.ReAllocHGlobal. This function only accepts an 'IntPtr' as a parameter

Can anyone tell me how to use the IntPtr parameter version of the function

Thanks
Stefan.

 

[Guest]

I could not find any hints in the MSDN library, but I did manage to test both versions of the functio
using the Win32 function 'GlobalSize'

And indeed the functioncalls
IntPtr p = Marshal.AllocHGlobal ( 20 )
an
IntPtr p = Marshal.AllocHGlobal ( new IntPtr ( 20 ) )

both allocate a memory block of 20 bytes.

 

[Mattias Sjögren]

Stefan,

Can anyone tell me how to use the IntPtr parameter version of the function?

You're using it right. The IntPtr overload could be useful on a 64-bit
implementation if you want to allocate more than 2GB of memory.



Mattias