Using DLLs with my Ruby app

Ruby
1

Hi,

A new ruby user here. I want to try using ruby to use an API for
accessing and retrieving data from a server. After doing some research I
learned about ruby/dl and tried the following in irb:

ENV[‘PATH’] += “;C\projects\test\lib” # to include the dependecies of
the API
require ‘dl/import’

extend DL::Importable

dlload “myAPI.dll”

extern “void serverLogon(string, string, string, void, void)”

but I get an error stating that the symbol “serverLogon” can’t be found.
I’m pretty sure that I have the correct function name, but I downloaded
this DLL Export viewer to see the function names, and the application
lists the exported function as “_serverLogon@20”. I tried using
“_serverLogon@20” in extern but I got a “can’t parse the function
prototype” error.

I don’t really have much experience with using dlls and I feel like I’m
missing something here. Can anyone clarify why I’m unable to use the
functions in the dll provided and why it has such odd names?

Many thanks!

  • Grish
2

Have you tried without the @20 on the end?

3

On 14 Jul 2009, at 11:19, Gin Mendi wrote:

extend DL::Importable

dlload “myAPI.dll”

extern “void serverLogon(string, string, string, void, void)”

try:

extern “void _serverLogon(string, string, string, void, void)”

Ellie

Eleanor McHugh
Games With Brains
http://slides.games-with-brains.net

raise ArgumentError unless @reality.responds_to? :reason

4

On 14 Jul 2009, at 19:53, Gin Mendi wrote:

  • which results to a “can’t parse the function prototype” error.
    I’m not on a Windows box so I can’t easily test how dll function
    signatures work, however I suspect the problem is with extern not
    supporting the ‘@’ embedded in the function signature. As an
    alternative you can try the following:

require ‘dl’
dll = DL.dlopen(‘myAPI.dll’)
server_logon = dll[‘_serverLogon’, ‘0SSS00’]
server_logon.call …

where the 0s indicate a void pointer, and … is replaced with your
parameter list.

Ellie

Eleanor McHugh
Games With Brains
http://slides.games-with-brains.net

raise ArgumentError unless @reality.responds_to? :reason

5

Thanks for the replies!

Yes I tried out both:

  1. extern “void _serverLogon(string, string, string, void, void)”
  • which results to a “cannot find symbol” error.

and

  1. extern “void _serverLogon@20(string, string, string, void, void)”
  • which results to a “can’t parse the function prototype” error.
6

Thanks Ellie, I’m making a bit of progress here, this is what I did.

require ‘dl’
dll = DL.dlopen(“myAPI.dll”)
server_logon = dll["_serverLogon@20", “0SSS00”]
result = server_logon.call(“user”, “pass”, “address”, nil, nil)

now I get “DL::DLTypeError: unknown type ‘0’ of the return value.”

I really don’t have any experience with C or DLLs but I went through the
function specs and I tried using another logon function:

Handle serverLogonEx(LPCSTR username, LPCSTR password, LPCSTR
servername, EVENT_NOTIFY notify, LPVOID userdata)

Handle is a type definition of LPVOID, while EVENT_NOTIFY is a function
callback. These are all a little new to me since I have no experience
with C but just reading online and putting things together. This is now
what I tried:

require ‘dl’
dll = DL.dlopen(“myAPI.dll”)
server_logon = dll["_serverLogonEx@20", “PcccPP”] # still putting @20
result = server_logon.call(“user”, “pass”, “some_address”, nil, nil)

and I get the following results:
OpenPipe error 1113 - \unknown type ‘0’ of the
return value.\pipe\dbserver

but I get a return from irb:
[nil, [117, 112, 49, nil, nil]]

I’m guessing the first element in that array is the returned value and
the 2nd element which is an array was my original paramters passed?
Perhaps I’m defining my function incorrectly?

7

Eleanor McHugh wrote in post #834844:

On 14 Jul 2009, at 11:19, Gin Mendi wrote:

extend DL::Importable

dlload “myAPI.dll”

extern “void serverLogon(string, string, string, void, void)”

try:

extern “void _serverLogon(string, string, string, void, void)”

Ellie

Eleanor McHugh
Games With Brains
http://slides.games-with-brains.net

raise ArgumentError unless @reality.responds_to? :reason

Hi, I am a newbiew to this to but I think I am way behind you in my
understanding. Can someone explain why the ‘extern’ is used here? Is it
mandatory to use this if you want to call a method from a dll?