C# How to correctly modify IntPtr and Marshal.Copy to switch from int to long?-CodePudding

The code in question (below) reads much faster (30x), tahn regular: MemoryMappedViewAccessor.ReadArray() I'm trying to modify the code to be able to read from long offset, not int (!)

    public unsafe byte[] ReadBytes(int offset, int num)
    {
        byte[] arr = new byte[num];
        byte *ptr = (byte*)0;
        this._view.SafeMemoryMappedViewHandle.AcquirePointer(ref ptr);
        Marshal.Copy(IntPtr.Add(new IntPtr(ptr), offset), arr, 0, num);
        this._view.SafeMemoryMappedViewHandle.ReleasePointer();
        return arr;
    }

original code is here: How can I quickly read bytes from a memory mapped file in .NET?_

I need to adjust IntPtr.Add and Marshal.Copy to correctly work with long offset Thank you in advance!

CodePudding user response：

new IntPtr(intPtr.ToInt64() longOffset)

Of course, this works in 64 bit processes only.

CodePudding user response：

Thank you, Klaus Gütter! Complete working code, based on your suggested method:

public static unsafe byte[] ReadBytes(long l_offset, int i_read_buf_size, MemoryMappedViewAccessor mmva)
    {
        byte[] arr = new byte[i_read_buf_size];
        byte* ptr = (byte*)0;
        mmva.SafeMemoryMappedViewHandle.AcquirePointer(ref ptr);
        IntPtr p = new(ptr);
        Marshal.Copy(new IntPtr(p.ToInt64()   l_offset), arr, 0, i_read_buf_size);
        mmva.SafeMemoryMappedViewHandle.ReleasePointer();
        return arr;
    }