Dynamic Memory Allocation in C#?

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It seems that in c# we should use Collection to avoid using dynamic array.
However, I am now using C# to use some unmanaged code in native C++ through a Managed C++ layer and encountered a problem here.

In my C++ code I have a loadFile function:

loadFile(const char* filename, byte* buffer)

which load the file content into the buffer.
I must use this function to load the file since it is compressed and encrypted.
I can't modify the code of the native c++.

I use this approach to load the file:
In c#:

ManagedDataFile DataFile = new ManagedDataFile(@"myPath");
DataFile.openDataFile();

byte[] filebuf = new byte[1024*30];
managedDataFile.loadFile(@"MyFileName", ref filebuf);

However, I can't control the memory allocation of the buffer "filebuf".
Can anyone suggest idea(s) for my situation?
Thanks a lot!

Posted 31-Jan-10 22:18pm

HideIvy

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2 solutions

Solution 3

You may want to look at the functions available in the System.Runtime.InteropServices.Marshal class and see if any of them may be of use.
Take a look at this article[^] it may help with your requirement.

Not sure if this will work but you could try this;

C#

IntPtr fileData_ptr = IntPtr.Zero;
try
{
  managedDataFile.loadFile(@"MyFileName", fileData_ptr);
  if (fileData_ptr != IntPtr.Zero)
  {
    IntPtr pData = managedDataFile.GlobalLock(fileData_ptr);
    IntPtr pArrayLocation = pData;

    Int32 uiSize = Marshal.ReadInt32(pData);

    byte[] filebuf = new byte[uiSize];
    Marshal.Copy(pArrayLocation, filebuf, 0, uiSize);

    managedDataFile.GlobalUnlock(pData);
    managedDataFile.GlobalFree(fileData_ptr);
  }
}
catch
{
}

Posted 31-Jan-10 22:58pm

Rod Kemp

Updated 31-Jan-10 23:42pm

v2

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Christian Graus · Accepted Answer · 2010-01-31T22:22:00

Solution 1

Write a managed C++ method which returns the size of the file.

Posted 31-Jan-10 22:22pm

Christian Graus