Win32 api format message with node-ffi - winapi

Question

I am trying to use node-ffi to interface with the win32 api FormatMessageA however I cannot seem to get the out lpBuffer parameter, here is a snippet of code to show what I have tried
'use strict';
const ref = require('ref');
const ffi = require('ffi');
const Kernel32 = ffi.Library('Kernel32.dll', {
FormatMessageA: ['ulong', [
'ulong', //flags
'void *',
'ulong', //status number
'ulong', //language
'uchar *',
'ulong',
'void *'
]]
});
const FORMAT_MESSAGE_FROM_SYSTEM = 0x1000;
const FORMAT_MESSAGE_ALLOCATE_BUFFER = 0x100;
const FORMAT_MESSAGE_IGNORE_INSERTS = 0x200;
const lpBuffer = ref.alloc('uchar *');
const result = Kernel32.FormatMessageA(
FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_IGNORE_INSERTS,
null,
0x80090300, //error code
0,
lpBuffer,
0,
null
);
console.log(result); //prints 57 bytes
I know function is successful as it returns 57 however I cannot get lpBuffer value which contains the error string I require.

Answer 1

As I stated in my 1st comment, according to [MSDN] FormatMessage function:
FORMAT_MESSAGE_ALLOCATE_BUFFER description:
The lpBuffer parameter is a pointer to an LPTSTR; you must cast the pointer to an LPTSTR (for example, (LPTSTR)&lpBuffer).
The (2nd) example at the bottom of the page:
// Some code (not relevant for this problem)
LPWSTR pBuffer = NULL;
// Some more code (still not relevant)
FormatMessage(FORMAT_MESSAGE_FROM_STRING |
FORMAT_MESSAGE_ALLOCATE_BUFFER,
pMessage,
0,
0,
(LPWSTR)&pBuffer,
// The rest of the code (not relevant)
when the dwFlags argument is composed of FORMAT_MESSAGE_ALLOCATE_BUFFER, the function expects that the lpBuffer argument which is a LPTSTR (pointer to TCHAR), to actually be a pointer to LPTSTR (double pointer to TCHAR) cast ed to LPTSTR.
That, translated in JS (that I have no experience with), would mean:
const lpBuffer = ref.alloc('uchar **');
Note: according to the same page, the buffer should be freed using LocalFree when it's no longer needed (makes sense, since FormatMessage allocates memory for it - that's why it requires to be a double pointer). Again, don't know how this would translate in JS (what I do know is that LocalFree should be called on an uchar *(dereferenced) buffer, not directly on lpBuffer).