WindowsInterop.cs

namespace VaListInterop
{
    using System;
    using System.Collections.Generic;
    using System.Linq;
    using System.Runtime.InteropServices;
    using System.Text;
    using System.Threading.Tasks;

    public static class WindowsInterop
    {
        /// <summary>
        /// Retrieves the address of an exported function or variable from the specified dynamic-link library (DLL).
        /// </summary>
        /// <param name="hModule">A handle to the DLL module that contains the function or variable.</param>
        /// <param name="lpProcName">he function or variable name, or the function's ordinal value. If this parameter is an ordinal value, it must be in the low-order word; the high-order word must be zero.</param>
        /// <returns>If the function succeeds, the return value is the address of the exported function or variable. If the function fails, the return value is NULL. To get extended error information, call GetLastError.</returns>
        [DllImport("kernel32", CharSet = CharSet.Ansi, ExactSpelling = true, SetLastError = true)]
        public static extern IntPtr GetProcAddress(IntPtr hModule, string lpProcName);

        /// <summary>
        /// Frees the loaded dynamic-link library (DLL) module and, if necessary, decrements its reference count. When the reference count reaches zero, the module is unloaded from the address space of the calling process and the handle is no longer valid.
        /// </summary>
        /// <param name="hModule">A handle to the loaded library module.</param>
        /// <returns>If the function succeeds, the return value is nonzero. If the function fails, the return value is zero. To get extended error information, call the GetLastError function.</returns>
        [DllImport("kernel32", SetLastError = true)]
        public static extern bool FreeLibrary(IntPtr hModule);

        /// <summary>
        /// Loads the specified module into the address space of the calling process. The specified module may cause other modules to be loaded.
        /// </summary>
        /// <param name="lpFileName">The name of the module. This can be either a library module (a .dll file) or an executable module (an .exe file). The name specified is the file name of the module and is not related to the name stored in the library module itself, as specified by the LIBRARY keyword in the module-definition (.def) file. If the string specifies a full path, the function searches only that path for the module. If the string specifies a relative path or a module name without a path, the function uses a standard search strategy to find the module; for more information, see the Remarks. If the function cannot find the module, the function fails. When specifying a path, be sure to use backslashes (\), not forward slashes (/). For more information about paths, see Naming a File or Directory. If the string specifies a module name without a path and the file name extension is omitted, the function appends the default library extension .dll to the module name. To prevent the function from appending .dll to the module name, include a trailing point character (.) in the module name string.</param>
        /// <returns>If the function succeeds, the return value is a handle to the module. If the function fails, the return value is NULL. To get extended error information, call GetLastError.</returns>
        [DllImport("kernel32", SetLastError = true)]
        public static extern IntPtr LoadLibrary(string lpFileName);


        /// <summary>
        /// Format a string using printf style markers
        /// </summary>
        /// <remarks>
        /// See https://stackoverflow.com/a/37629480/2663813
        /// </remarks>
        /// <param name="buffer">The output buffer (should be large enough, use _vscprintf)</param>
        /// <param name="format">The message format</param>
        /// <param name="args">The variable arguments list pointer. We do not know what it is, but the pointer must be given as-is from C back to sprintf.</param>
        /// <returns>A negative value on failure, the number of characters written otherwise.</returns>
        [DllImport("msvcrt.dll", CharSet = CharSet.Ansi, CallingConvention = CallingConvention.Cdecl)]
        public static extern int vsprintf(
            IntPtr buffer,
            string format,
            IntPtr args);

        /// <summary>
        /// Compute the size required by vsprintf to print the parameters.
        /// </summary>
        /// <param name="format"></param>
        /// <param name="args"></param>
        /// <returns></returns>
        [DllImport("msvcrt.dll", CallingConvention = CallingConvention.Cdecl)]
        public static extern int _vscprintf(
            string format,
            IntPtr args);
    }

    /// <summary>
    /// The va_list structure of windows
    /// </summary>
    [StructLayout(LayoutKind.Sequential, Pack = 4)]
    public struct VaListWindows
    {
        private IntPtr Pointer;
    }
}