Interop.CreateFileMapping C# (CSharp) Method

    public static SafeMemoryMappedFileHandle CreateFileMapping(
            IntPtr hFile,
            ref Kernel32.SECURITY_ATTRIBUTES securityAttributes,
            int pageProtection,
            long maximumSize,
            string name)
    {
        // split the long into two ints
        int capacityHigh, capacityLow;
        SplitLong(maximumSize, out capacityHigh, out capacityLow);

        return Interop.Kernel32.CreateFileMapping(hFile, ref securityAttributes, pageProtection, capacityHigh, capacityLow, name);
    }

        /// <summary>
        /// Used by the 2 Create factory method groups.  A null fileHandle specifies that the
        /// memory mapped file should not be associated with an existing file on disk (i.e. start
        /// out empty).
        /// </summary>
        private static SafeMemoryMappedFileHandle CreateCore(
            SafeFileHandle?fileHandle, string?mapName, HandleInheritability inheritability,
            MemoryMappedFileAccess access, MemoryMappedFileOptions options, long capacity, long fileSize)
        {
            Debug.Assert(fileHandle is null || fileSize >= 0);

            Interop.Kernel32.SECURITY_ATTRIBUTES secAttrs = GetSecAttrs(inheritability);

            if (fileHandle != null)
            {
                VerifyMemoryMappedFileAccess(access, capacity, fileSize);
            }

            SafeMemoryMappedFileHandle handle = fileHandle != null?
                                                Interop.CreateFileMapping(fileHandle, ref secAttrs, GetPageAccess(access) | (int)options, capacity, mapName) :
                                                    Interop.CreateFileMapping(new IntPtr(-1), ref secAttrs, GetPageAccess(access) | (int)options, capacity, mapName);

            int errorCode = Marshal.GetLastPInvokeError();

            if (!handle.IsInvalid)
            {
                if (errorCode == Interop.Errors.ERROR_ALREADY_EXISTS)
                {
                    handle.Dispose();
                    throw Win32Marshal.GetExceptionForWin32Error(errorCode);
                }
            }
            else // handle.IsInvalid
            {
                handle.Dispose();
                throw Win32Marshal.GetExceptionForWin32Error(errorCode);
            }

            return(handle);
        }