On 6/3/2013 18:54, Hans-Peter Diettrich wrote:
waldo kitty schrieb:
what can we do about INVALID_FILE_SIZE?
const
INVALID_FILE_SIZE = DWORD($FFFFFFFF);
is the above correct? it would seem to be from what i can make out from MSDN
and the various C code files i've found it defined in...
Using unsigned constants with int64 filesizes would classify files of exactly
that size as invalid, while smaller or bigger files would be valid. This
certainly is *not* what the coder had in mind, so that I'd suggest to inspect
and fix all occurences of this (and similar) unsigned constants in user code.
i'm (finally) back to trying to poke this conversion thing with a sharp stick...
i understand what you are saying in the above but i don't know how to "fix all
occurrences of this (and similar) unsigned constants in user code."... i'm sure
it is probably something easy that i'm not seeing... something like adding a sign ;)
eg: INVALID_FILE_SIZE = DWORD(-1);
but how can i know if that will be what OS API functions send back? the above
const is documented as shown above in the DWORD form so i already know that that
particular instance from that particular API function will fail... since
DWORD($FFFFFFFF) <> -1...
i kind of have to laugh because on place i read spoke of examples checking the
result directly instead of using INVALID_FILE_SIZE and that this was not good
coding practice because m$ might change the value of INVALID_FILE_SIZE at any
time which would then break all of that code... i makes sense to me O:)
IMO such unsigned constants should be used only in specific cases, e.g. with OS
defined records containing part of an longer (int64) type. The FCL can use that
constant in Win32 platform code, the LCL or user code never should use it at
all.
i understand this... how can i get this const (as defined) into the FCL if it
does not already exist? how can i tell my converted delphi project to use the
FCL in addition to the LCL? right now when i look at the project inspector, the
LCL is the only "required" package shown...
I also doubt that the MS documentation is up to date whenever above constant is
used with anything except struct fields of type DWORD. Even in 32 bit code
*both* low/high parts of a 64 bit filesize must be checked for
INVALID_FILE_SIZE, in order to determine a valid result.
the documentation for the above const (which i linked to previously) talks about
using a different OS API function for those instances where necessary...
--
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