Re: Writing to memory buffer in a .dll?

Am 30.08.2013 22:47, schrieb Brad Basler:
> I am attempting to use Python w/ctypes to control an embedded
> programming tool (see UM0151, STMicroelectronics).
>
> I had this working before as a basic test, but not really realizing what
> I'm doing differently now. I do not seem to be writing to the code image.
>
> Here's the function prototype I am trying to interface with.
> Prototype: char far *EGetImagePtr(DWORD dwAreaId, long *MemSize)
>
> This returns a pointer that is allocated on the heap by the .dll
>
> I can read from this buffer, but I don't appear to be able to write to it.
>
>
> where my function was defined by:
>       EPRCore.dll_eprcore.EGetImagePtr.argtypes =
> [ctypes.c_uint,ctypes.c_void_p]
>
>       EPRCore.dll_eprcore.EGetImagePtr.restype =
> ctypes.POINTER(ctypes.c_char)
>
>
>
>
> ptr = self.myEPR.EGetImagePtr(self.memHandle,ctypes.byref(self.memSize))
> ptr[0x8112] = 0x00;
> ptr[0x8113] = 0x01;
> ptr[0x8114] = 0x02;
> ptr[0x8115] = 0x03;

Well, if ptr is really a POINTER(c_char) instance then the above lines
should raise an error:

 >>> p[0] = 0x00
Traceback (most recent call last):
   File "<stdin>", line 1, in <module>
TypeError: one character string expected
 >>>

Thomas


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