OPENFILENAMEA

using System;
using System.Runtime.InteropServices;

[StructLayout(LayoutKind.Sequential, Pack = 1, CharSet = CharSet.Unicode)]
public struct OPENFILENAMEA
{
    public uint lStructSize;
    public IntPtr hwndOwner;
    public IntPtr hInstance;
    public IntPtr lpstrFilter;
    public IntPtr lpstrCustomFilter;
    public uint nMaxCustFilter;
    public uint nFilterIndex;
    public IntPtr lpstrFile;
    public uint nMaxFile;
    public IntPtr lpstrFileTitle;
    public uint nMaxFileTitle;
    public IntPtr lpstrInitialDir;
    public IntPtr lpstrTitle;
    public uint Flags;
    public ushort nFileOffset;
    public ushort nFileExtension;
    public IntPtr lpstrDefExt;
    public IntPtr lCustData;
    public IntPtr lpfnHook;
    public IntPtr lpTemplateName;
    public IntPtr pvReserved;
    public uint dwReserved;
    public uint FlagsEx;
}

Imports System.Runtime.InteropServices

<StructLayout(LayoutKind.Sequential, Pack:=1, CharSet:=CharSet.Unicode)>
Public Structure OPENFILENAMEA
    Public lStructSize As UInteger
    Public hwndOwner As IntPtr
    Public hInstance As IntPtr
    Public lpstrFilter As IntPtr
    Public lpstrCustomFilter As IntPtr
    Public nMaxCustFilter As UInteger
    Public nFilterIndex As UInteger
    Public lpstrFile As IntPtr
    Public nMaxFile As UInteger
    Public lpstrFileTitle As IntPtr
    Public nMaxFileTitle As UInteger
    Public lpstrInitialDir As IntPtr
    Public lpstrTitle As IntPtr
    Public Flags As UInteger
    Public nFileOffset As UShort
    Public nFileExtension As UShort
    Public lpstrDefExt As IntPtr
    Public lCustData As IntPtr
    Public lpfnHook As IntPtr
    Public lpTemplateName As IntPtr
    Public pvReserved As IntPtr
    Public dwReserved As UInteger
    Public FlagsEx As UInteger
End Structure

import ctypes
from ctypes import wintypes

class OPENFILENAMEA(ctypes.Structure):
    _pack_ = 1
    _fields_ = [
        ("lStructSize", wintypes.DWORD),
        ("hwndOwner", ctypes.c_void_p),
        ("hInstance", ctypes.c_void_p),
        ("lpstrFilter", ctypes.c_void_p),
        ("lpstrCustomFilter", ctypes.c_void_p),
        ("nMaxCustFilter", wintypes.DWORD),
        ("nFilterIndex", wintypes.DWORD),
        ("lpstrFile", ctypes.c_void_p),
        ("nMaxFile", wintypes.DWORD),
        ("lpstrFileTitle", ctypes.c_void_p),
        ("nMaxFileTitle", wintypes.DWORD),
        ("lpstrInitialDir", ctypes.c_void_p),
        ("lpstrTitle", ctypes.c_void_p),
        ("Flags", wintypes.DWORD),
        ("nFileOffset", ctypes.c_ushort),
        ("nFileExtension", ctypes.c_ushort),
        ("lpstrDefExt", ctypes.c_void_p),
        ("lCustData", ctypes.c_ssize_t),
        ("lpfnHook", ctypes.c_void_p),
        ("lpTemplateName", ctypes.c_void_p),
        ("pvReserved", ctypes.c_void_p),
        ("dwReserved", wintypes.DWORD),
        ("FlagsEx", wintypes.DWORD),
    ]

#[repr(C, packed(1))]
pub struct OPENFILENAMEA {
    pub lStructSize: u32,
    pub hwndOwner: *mut core::ffi::c_void,
    pub hInstance: *mut core::ffi::c_void,
    pub lpstrFilter: *mut core::ffi::c_void,
    pub lpstrCustomFilter: *mut core::ffi::c_void,
    pub nMaxCustFilter: u32,
    pub nFilterIndex: u32,
    pub lpstrFile: *mut core::ffi::c_void,
    pub nMaxFile: u32,
    pub lpstrFileTitle: *mut core::ffi::c_void,
    pub nMaxFileTitle: u32,
    pub lpstrInitialDir: *mut core::ffi::c_void,
    pub lpstrTitle: *mut core::ffi::c_void,
    pub Flags: u32,
    pub nFileOffset: u16,
    pub nFileExtension: u16,
    pub lpstrDefExt: *mut core::ffi::c_void,
    pub lCustData: isize,
    pub lpfnHook: *mut core::ffi::c_void,
    pub lpTemplateName: *mut core::ffi::c_void,
    pub pvReserved: *mut core::ffi::c_void,
    pub dwReserved: u32,
    pub FlagsEx: u32,
}

import "golang.org/x/sys/windows"

type OPENFILENAMEA struct {
	lStructSize uint32
	hwndOwner uintptr
	hInstance uintptr
	lpstrFilter uintptr
	lpstrCustomFilter uintptr
	nMaxCustFilter uint32
	nFilterIndex uint32
	lpstrFile uintptr
	nMaxFile uint32
	lpstrFileTitle uintptr
	nMaxFileTitle uint32
	lpstrInitialDir uintptr
	lpstrTitle uintptr
	Flags uint32
	nFileOffset uint16
	nFileExtension uint16
	lpstrDefExt uintptr
	lCustData uintptr
	lpfnHook uintptr
	lpTemplateName uintptr
	pvReserved uintptr
	dwReserved uint32
	FlagsEx uint32
}

type
  OPENFILENAMEA = packed record
    lStructSize: DWORD;
    hwndOwner: Pointer;
    hInstance: Pointer;
    lpstrFilter: Pointer;
    lpstrCustomFilter: Pointer;
    nMaxCustFilter: DWORD;
    nFilterIndex: DWORD;
    lpstrFile: Pointer;
    nMaxFile: DWORD;
    lpstrFileTitle: Pointer;
    nMaxFileTitle: DWORD;
    lpstrInitialDir: Pointer;
    lpstrTitle: Pointer;
    Flags: DWORD;
    nFileOffset: Word;
    nFileExtension: Word;
    lpstrDefExt: Pointer;
    lCustData: NativeInt;
    lpfnHook: Pointer;
    lpTemplateName: Pointer;
    pvReserved: Pointer;
    dwReserved: DWORD;
    FlagsEx: DWORD;
  end;

const OPENFILENAMEA = extern struct {
    lStructSize: u32,
    hwndOwner: ?*anyopaque,
    hInstance: ?*anyopaque,
    lpstrFilter: ?*anyopaque,
    lpstrCustomFilter: ?*anyopaque,
    nMaxCustFilter: u32,
    nFilterIndex: u32,
    lpstrFile: ?*anyopaque,
    nMaxFile: u32,
    lpstrFileTitle: ?*anyopaque,
    nMaxFileTitle: u32,
    lpstrInitialDir: ?*anyopaque,
    lpstrTitle: ?*anyopaque,
    Flags: u32,
    nFileOffset: u16,
    nFileExtension: u16,
    lpstrDefExt: ?*anyopaque,
    lCustData: isize,
    lpfnHook: ?*anyopaque,
    lpTemplateName: ?*anyopaque,
    pvReserved: ?*anyopaque,
    dwReserved: u32,
    FlagsEx: u32,
};

type
  OPENFILENAMEA {.packed.} = object
    lStructSize: uint32
    hwndOwner: pointer
    hInstance: pointer
    lpstrFilter: pointer
    lpstrCustomFilter: pointer
    nMaxCustFilter: uint32
    nFilterIndex: uint32
    lpstrFile: pointer
    nMaxFile: uint32
    lpstrFileTitle: pointer
    nMaxFileTitle: uint32
    lpstrInitialDir: pointer
    lpstrTitle: pointer
    Flags: uint32
    nFileOffset: uint16
    nFileExtension: uint16
    lpstrDefExt: pointer
    lCustData: int
    lpfnHook: pointer
    lpTemplateName: pointer
    pvReserved: pointer
    dwReserved: uint32
    FlagsEx: uint32

align(1)
struct OPENFILENAMEA
{
    uint lStructSize;
    void* hwndOwner;
    void* hInstance;
    void* lpstrFilter;
    void* lpstrCustomFilter;
    uint nMaxCustFilter;
    uint nFilterIndex;
    void* lpstrFile;
    uint nMaxFile;
    void* lpstrFileTitle;
    uint nMaxFileTitle;
    void* lpstrInitialDir;
    void* lpstrTitle;
    uint Flags;
    ushort nFileOffset;
    ushort nFileExtension;
    void* lpstrDefExt;
    ptrdiff_t lCustData;
    void* lpfnHook;
    void* lpTemplateName;
    void* pvReserved;
    uint dwReserved;
    uint FlagsEx;
}