From: Shashank Date <sdate@...>
Date: 2002-10-21T06:31:50+09:00
Subject: Re: async system call on Windows?

Thanks a lot !

"Chris Morris" <chrismo@clabs.org> wrote in message
news:016701c2764c$68c61800$6401a8c0@3ComC...
> > I am interested in learning from your Ruby code ... if it is available
for
> > public consumption, that is.
>
> Sure - here you go. Thx to Phil Tomson for posting a version of his
> CreateProcess in the archives which helped unstick me (I'd been trying 'P'
> and empty string for nil pointers, which I've seen work, but didn't work
> with CreateProcess. He used 'L' and 0 for nil pointers, and it worked
great)
>
> def async_system(command)
>   #
>
http://msdn.microsoft.com/library/en-us/vccore98/html/_crt__spawnv.2c_._wspa
> wnv.asp
>   # this is working -- but frequently Segfaults ruby 1.6.6 mswin32
>
>   spawn = Win32API.new("crtdll", "_spawnvp", ['I', 'P', 'P'] ,'L')
>   # need to try the third param as an 'L' and pass it 0, maybe segfault
>   # will go away?
>   res = spawn.Call(P_NOWAIT, command, '')
>   if res == -1
>     Win32API.new("crtdll", "perror", ['P'], 'V').call('async_system')
>   end
>   res
> end
>
> # from WinBase.h in SDK
> # dwCreationFlag values
> NORMAL_PRIORITY_CLASS = 0x00000020
>
> STARTUP_INFO_SIZE = 68
> PROCESS_INFO_SIZE = 16
>
> def create_process(command)
>   # from WinBase.h in SDK
>   # Passing nil for a pointer -- I've seen it work with a P type param and
>   # an empty string ... here L with a 0 is the only way that works with
>   # CreateProcess. (see FormatMessage in raise_last_win32_error for an
>   # example of 'P' and '' that works)
>   params = [
>     'L', # IN LPCSTR lpApplicationName
>     'P', # IN LPSTR lpCommandLine
>     'L', # IN LPSECURITY_ATTRIBUTES lpProcessAttributes
>     'L', # IN LPSECURITY_ATTRIBUTES lpThreadAttributes
>     'L', # IN BOOL bInheritHandles
>     'L', # IN DWORD dwCreationFlags
>     'L', # IN LPVOID lpEnvironment
>     'L', # IN LPCSTR lpCurrentDirectory
>     'P', # IN LPSTARTUPINFOA lpStartupInfo
>     'P'  # OUT LPPROCESS_INFORMATION lpProcessInformation
>   ]
>   returnValue = 'I' # BOOL
>
>   startupInfo = [STARTUP_INFO_SIZE].pack('I') + ([0].pack('I') *
> (STARTUP_INFO_SIZE - 4))
>   processInfo = [0].pack('I') * PROCESS_INFO_SIZE
>   createProcess = Win32API.new("kernel32", "CreateProcess", params,
> returnValue)
>   if createProcess.call(0, command, 0, 0, 0, NORMAL_PRIORITY_CLASS, 0, 0,
>     startupInfo, processInfo) == 0
>     raise_last_win_32_error
>   end
>   processInfo
> end
>
> ERROR_SUCCESS = 0x00
> FORMAT_MESSAGE_FROM_SYSTEM = 0x1000
> FORMAT_MESSAGE_ARGUMENT_ARRAY = 0x2000
>
> def raise_last_win_32_error
>   errorCode = Win32API.new("kernel32", "GetLastError", [], 'L').call
>   if errorCode != ERROR_SUCCESS
>     params = [
>       'L', # IN DWORD dwFlags,
>       'P', # IN LPCVOID lpSource,
>       'L', # IN DWORD dwMessageId,
>       'L', # IN DWORD dwLanguageId,
>       'P', # OUT LPSTR lpBuffer,
>       'L', # IN DWORD nSize,
>       'P', # IN va_list *Arguments
>     ]
>
>     formatMessage = Win32API.new("kernel32", "FormatMessage", params, 'L')
>     msg = ' ' * 255
>     msgLength = formatMessage.call(FORMAT_MESSAGE_FROM_SYSTEM +
>       FORMAT_MESSAGE_ARGUMENT_ARRAY, '', errorCode, 0, msg, 255, '')
>     msg.gsub!("\\000", '')
>     msg.strip!
>     raise msg
>   else
>     raise 'GetLastError returned ERROR_SUCCESS'
>   end
> end
>
> All this code is BSD license - full code is part of a misc windows utility
> unit you can find here:
>
>
http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/scrapware/scrapware/ruby/cl/u
> til/win.rb?rev=1.13&content-type=text/vnd.viewcvs-markup
>
> Chris
>
>