win32-api

FFI Definitions of Windows win32 api for node-ffi

What can I do with this?

Calling win32 native functions come from user32.dll, kernel32.dll, comctl32.dll by Node.js

Installing

npm install --save win32-api

Usage

// find calc's hWnd, need run a calculator program manually at first
/**
 * expose module:
 * C, Comctl32 for Comctl32 from lib/comctl32/api
 * K, Kernel32 for kernel32 from lib/kernel32/api
 * U, User32 for user32 from lib/user32/api
 */
const {K, U} = require('win32-api');   // or {Kernel32, User32}
const ref = require('ref');

const knl32 = K.load();
const user32 = U.load();  // load all apis defined in lib/{dll}/api from user32.dll
// const user32 = U.load(['FindWindowExW']);  // load only one api defined in lib/{dll}/api from user32.dll

const title = 'Calculator\0';    // null-terminated string
// const title = '计算器\0';    // string in chinese

const lpszWindow = Buffer.from(title, 'ucs2');
const hWnd = user32.FindWindowExW(null, null, null, lpszWindow);

if (hWnd && ! hWnd.isNull()) {
  // Caution: output hWnd will cuase exception in the following process, even next script!
  // So do NOT do this in the production code!
  // console.log('buf: ', hWnd); // avoid this
  console.log('buf: ', ref.address(hWnd)); // this is ok

  // Change title of the Calculator
  const res = user32.SetWindowTextW(hWnd, Buffer.from('Node-Calculator\0', 'ucs2'));

  if ( ! res) {
    // See: [System Error Codes] below
    const errcode = knl32.GetLastError();
    const len = 255;
    const buf = Buffer.alloc(len);
    const p = 0x00001000 | 0x00000200;  // FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS
    const langid = 0x0409;              // 0x0409: US, 0x0000: Neutral locale language
    const msglen = knl32.FormatMessageW(p, null, errcode, langid, buf, len, null);

    if (msglen) {
      console.log(ref.reinterpretUntilZeros(buf, 2).toString('ucs2'));
    }
  }
  else {
    console.log('window title changed');
  }
}

// use the types exposed by the module for TypeScript dev
import { U } from 'win32-api';
import * as ref from 'ref';

// so we can all agree that a buffer with the int value written
// to it could be represented as an "int *"
const buf  = Buffer.alloc(4);
buf.writeInt32LE(12345, 0);

const hex = ref.hexAddress(buf);
console.log(typeof hex);
console.log(hex);  // ← '7FA89D006FD8'

buf.type = ref.types.int;  // @ts-ignore

// now we can dereference to get the "meaningful" value
console.log(ref.deref(buf));  // ← 12345

// struct usage by ref-struct
import * as Struct from 'ref-struct';
import { DStruct as DS } from 'win32-api';

// https://msdn.microsoft.com/en-us/library/windows/desktop/dd162805(v=vs.85).aspx
const point = new Struct(DS.POINT)();
point.x = 100;
point.y = 200;
console.log(point);

// usage of types and windef:
import { K, FModel as FM, DTypes as W } from 'win32-api';
import * as ref from 'ref';

const knl32 = K.load();

const buf  =  Buffer.alloc(4);   // ← here the types
buf.writeInt32LE(12345, 0);

// const hInstance = Buffer.alloc(process.arch === 'x64' ? 8 : 4);
const hInstance =  ref.alloc(W.HINSTANCE);    // W.HINSTANCE is 'int64*' under x64, 'int32*' under ia32
knl32.GetModuleHandleExW(0, null, hInstance);

Demo

• create_window

Dependencies Troubleshooting

• If installation of node-gyp fails: Check out node-gyp and windows-build-tools

Relevant

• Windows Api documentation
• Windows Data Types
• System Error Codes
• FFI doc
• ref doc
• ref-struct

License

MIT

Languages

• English
• 中文