OpenEuphoria

Re: 64 bit integers (accessing files > 4Gb)

• Posted by Matt Lewis <matthewwalkerlewis at gmail.com> Jan 31, 2007
• 503 views

CChris wrote:
> 
> Chris Bensler wrote:
> > 
> > How do I access file data > 4Gb?
> > 
> > The Windows API has SetFilePointerEx() but it requires large integers.
> > Is it possible to deal with large ints in Eu using atoms?
> > 
> 
> I didn't test this, but....
> 
> In the wrapper for your routine, replace the large_integer by a C_LONG and 
> a C_ULONG. Then, pass the high dword in the C_LONG and the low dword in the
> 
> C_LONG, both using atoms as usual. This results in
> 
> }}}
<eucode>
> constant kernel32=open_dll("kernel32.dll"),
> sfpx=define_c_func(kernel32,"SetFilePointerEx",
>   {C_POINTER,C_LONG,C_ULONG,C_POINTER,C_ULONG},C_BOOL)
> </eucode>
{{{

> 
> You'd pass 5 atoms to c_func() when calling the function. You'd also 
> poke4() 2 atoms at the place pointed to by the 4th arg, which is the
> lpNewFilePointer parameter. 
> 
> If the large integer is pushed on the stack, which I expect on 32 bit 
> machines, this hack should work, since it generates the stack layout the 
> routine expects. Perhaps using a "+" to force a _cdecl call is safer. 
> Again, I haven't tested this...

No, definitely do *not* use cdecl for calling the Win32 API.  Otherwise,
your directions are correct.  I've used these functions before, and you
can simply break up the LARGE_INTEGER into two 32-bit integers.  You
just have to 'manually' do the 64-bit math and increment the high
dword yourself.

Matt