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Can't use FindWindow from user32 library

See original GitHub issue

I’m trying to call FindWindow from user32.dll, i got working perfectly an example that shows a MessageBox but with this code nodejs crashed and I can’t figure out why

var user32 = new FFI.Library('user32', {
    'FindWindow': [
      'pointer', [ 'string', 'string']
    ]
    });

    var process = user32.FindWindow(NULL,"Calculadora")
    console.log("Process ID", process)

Error:

Error: Dynamic Symbol Retrieval Error: "FindWindow": Controlador no vï¿½lido.
    at DynamicLibrary.get (C:\Program Files (x86)\nodejs\node_modules\node-ffi\lib\dynamic_library.js:81:11)
    at C:\Program Files (x86)\nodejs\node_modules\node-ffi\lib\library.js:19:21
    at Array.forEach (native)
    at new Library (C:\Program Files (x86)\nodejs\node_modules\node-ffi\lib\library.js:18:24)
    at C:\Program Files (x86)\nodejs\diablo.js:18:18
    at callbacks (C:\Program Files (x86)\nodejs\node_modules\express\lib\router\index.js:272:11)
    at param (C:\Program Files (x86)\nodejs\node_modules\express\lib\router\index.js:246:11)
    at pass (C:\Program Files (x86)\nodejs\node_modules\express\lib\router\index.js:253:5)
    at Router._dispatch (C:\Program Files (x86)\nodejs\node_modules\express\lib\router\index.js:280:4)
    at Object.handle (C:\Program Files (x86)\nodejs\node_modules\express\lib\router\index.js:45:10)

Issue Analytics

State:
Created 11 years ago
Comments:8 (5 by maintainers)

Top GitHub Comments

4reactions

SkaceKamencommented, Mar 15, 2017

For anyone coming from google (like me): utf-16 requires 2 NULLs at the end, so correct implementation is (updated to work with newer ffi):

var lpctstr = {
    name: 'lpctstr',
    indirection: 1,
    size: ref.sizeof.pointer,
    get: function(buffer, offset) {
        var _buf = buffer.readPointer(offset);
        if(_buf.isNull()) {
            return null;
        }
        return _buf.readCString(0);
    },
    set: function(buffer, offset, value) {
        var _buf = new Buffer(Buffer.byteLength(value, 'ucs2') + 2)
        _buf.write(value, 'ucs2')
        _buf[_buf.length - 2] = 0
        _buf[_buf.length - 1] = 0
        return buffer.writePointer(_buf, offset)
    },
    ffi_type: ffi.types.CString.ffi_type
}

0reactions

TooTallNatecommented, May 29, 2012

Well with node-ffi v1.0, you can define a Ucs2String type and define your ffi’d functions with that as an argument type. That way you could pass in regular JS strings to the function and node-ffi would create the proper Buffer with the string written to it.

Something like this should work:

var Ucs2String = {
  indirection: 1,
  size: ref.sizeof.pointer,
  get: function (buffer, offset) {
    var _buf = buffer.readPointer(offset)
    // TODO: a *real* way to detect the end of the ucs2 string. this is a band-aid...
    return _buf.reinterpret(10000).toString('ucs2')
  },
  set: function (buffer, offset, string) {
    var _buf = new Buffer(Buffer.byteLength(string, 'ucs2') + 1)
    _buf.write(string, 'ucs2')
    _buf[_buf.length - 1] = 0
    return buffer.writePointer(_buf, offset)
  }
}

var user32 = ffi.Library('user32', {
  'FindWindowW': [
    'pointer', [ Ucs2String, Ucs2String ]
  ]
})

user32.FindWindowW(null, 'Calculadora')