Problem with access to shared memory(W2K) / ORIGINALLY (win32) speedfan api control

[Thomas Heller]

"Claudio Grondi" <claudio.grondi at freenet.de> writes:

> Background information:
> ---------------------------------
> in order to monitor mainboard sensory data
> as fan speeds, temperatures, applications
> like SpeedFan http://www.almico.com/speedfan.php
> or MBM http://mbm.livewiredev.com/
> can be used.
> Both of the mentioned apps expose data got
> from the hardware in a shared memory area.
>
> The goal to achieve:
> ---------------------------
> is to supervise the motherboard sensory
> data from within a Python script
>
> The approach:
> -------------------
> access to the shared memory area
> exposed by motherboard hardware
> querying apps from Python script.

For the mistake you made see below, hope that helps.

For the general way to solve this problem you should know that you can
access a shared memory area with a certain name also with Python's mmap
module, although that is probably not documented very good.  There was a
recipe posted a few days ago which showed different ways to acces shared
memory, with or without ctypes.

> The problem:
> -----------------
> the below listed script code returns
> always same values, what
> leads to the conclusion, that something
> is going wrong.
>
> Can anyone help?
>
> Thanks in advance
>
> Claudio
>
> The code
> -------------
>   I use is provided also here:
>  http://www.codecomments.com/Python/message430495.html
>  http://mail.python.org/pipermail/python-list/2005-March/271853.html
> (the mmap part of it doesn't work at all)
>
> from ctypes import *
>
> class Buffer(Structure):
>   # just to see if any useful data can be acquired
>   _fields_ = [
>     ("Data0", c_longlong)
>    ,("Data1", c_longlong)
>    ,("Data2", c_longlong)
>    ,("Data3", c_longlong)
>    ,("Data4", c_longlong)
>    ,("Data5", c_longlong)
>    ,("Data6", c_longlong)
>    ,("Data7", c_longlong)
>    ,("Data8", c_longlong)
>    ,("Data9", c_longlong)
>    ,("DataA", c_longlong)
>    ,("DataB", c_longlong)
>    ,("DataC", c_longlong)
>    ,("DataD", c_longlong)
>    ,("DataE", c_longlong)
>    ,("DataF", c_longlong)
>   ]
>
> szName = c_char_p("SFSharedMemory_ALM")  # SpeedFan
> szName = c_char_p("$M$B$M$5$S$D$")    # MBM
> # szName = c_char_p("blabla")  # not existing shared memory
>
> FILE_MAP_ALL_ACCESS  = 0xF001F
> FALSE = 0
>
> hMapObject = windll.kernel32.OpenFileMappingA(
>    FILE_MAP_ALL_ACCESS
>   ,FALSE
>   ,szName
> )
> if (hMapObject == 0):
>   print "Could not open file mapping object"
>   raise WinError()
>
> pBuf = windll.kernel32.MapViewOfFile(
>      hMapObject
>     ,FILE_MAP_ALL_ACCESS
>     ,0
>     ,0
>     ,0
> )
>
>   if (pBuf == 0):
>     print "Could not map view of file"
>     raise WinError()
>   else:
>     print repr(pBuf)
>     print repr(hMapObject)
>
>     pBuf_str = cast(pBuf, c_char_p)
>     print repr(pBuf_str.value)
>     print repr(pBuf_str)
>
>     pBuf_buf = cast(pBuf, Buffer)
Here's the problem.  pBuf is a pointer to a Buffer structure, not the
buffer structure itself.
Something like
    pBuf_buf = Buffer.from_address(pBuf)
may work.

Thomas