[Win32utils-devel] Yet another data structure + pack/unpack question (win32-service)

Heesob Park phasis at gmail.com
Wed Jun 21 01:59:53 EDT 2006


Hi,

2006/6/21, Daniel Berger <djberg96 at gmail.com>:
> Hi all,
>
> If you take a look at the service.rb file in the win32-service
> repository (the new one in the toplevel repository path), I've got this
> bit of code, which succeeds, but I can't seem to unpack the data
> structure properly.  Did I pack it wrong to begin with?  I should know
> this but I'm spacing out.
>
> proc_status       = [0,0,0,0,0,0,0,0,0,0].pack('LLLLLLLLLL')
> enum_service      = [0.chr, 0.chr].pack('pp') + proc_status
> service_buf       = enum_service * 1000
> bytes_needed      = [0].pack('L')
> services_returned = [0].pack('L')
> resume_handle     = [0].pack('L')
>
> bool = EnumServicesStatusEx(
>   handle_scm,
>   SC_ENUM_PROCESS_INFO,
>   SERVICE_WIN32 | SERVICE_DRIVER,
>   SERVICE_STATE_ALL,
>   service_buf,
>   service_buf.size,
>   bytes_needed,
>   services_returned,
>   resume_handle,
>   group
> )
>
> if bool
>   num_services = services_returned.unpack('L').first
>   index = 0
>
>   1.upto(num_services){ |num|
>      info = service_buf[index, enum_service.size-1]
>      service_name = info[0,4].pack('p') # boom!
>      index += enum_service.size
>   }
> end
>
I guess you still don't understand the difference of C pointer and
ruby buffer :)

Try this:

Strcpy  = Win32API.new('msvcrt', 'strcpy', 'PL', 'L')

 1.upto(num_services){ |num|
     info = service_buf[index, enum_service.size-1]
     service_name = 0.chr * 256
     Strcpy.call(service_name,info[0,4].unpack('L').first)
     service_name = service_name.strip
     index += enum_service.size
  }

But, the code still segfault for another bug.

Regards,

Park Heesob


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