pointer-to-two-adjactend-chars

**Victor Bazarov** · Sep 24 '08, 05:55 PM

Re: pointer-to-two-adjactend-chars

..rhavin grobert wrote:

this is m$ vc++, but the question itself is c++ specific...
>
TCHAR is a 'char' in non-unicode.
>
functions return...
TCHAR* CString::GetBuf fer(int);
int CString::GetLen ght(int);
_______________ _______________ ____________
>
// code:
>
CString str ="SomeStringWit hMoreThanOneTCh ar";
TCHAR *(pEnd[2]) = /* § */ str.GetBuffer(s tr.GetLength()) +
str.GetLength() - 2;

So, 'pEnd' is *an array of two pointers to TCHAR*. You can't initialise
an array with a pointer in C++. The only special case is initialisation
of an array of char with a literal, but it doesn't apply here.

// in other words: a pointer to the second-last TCHAR is returned
_______________ _______________ ____________
>
in the place marked "/* § */", a cast is neccesary. My problem: i dont
find the correct syntax.

There isn't any, most likely.

the error given is "cannot convert from 'char *' to 'char *[2]' ", but
inserting
>
(char *[2]), (char (*[2])), ((char*) [2]) or (*(char[2])) doesnt work.
Anyone knows the correct syntax for a cast to a pointer-to-two-
adjactend-TCHARs please?
>

There is no such type as *a pointer to two adjacent TCHAR*. There can
be a pointer to an array of two TCHAR, which is

TCHAR (*pEnd)[2]

or a simple pointer to TCHAR, which you already know

TCHAR *pEnd

Now, the assuredness that there is a second TCHAR that follows the one
to which that pointer would point, cannot really be expressed by means
of the language itself, AFAIK.

If you want to use a pointer to an array of two TCHAR, you can do

TCHAR (*pEnd)[2] = reinterpret_cas t<TCHAR(*)[2]>(...

but one problem with it is that you need to dereference the pointer
before you can index within the array:

(*pEnd)[0]; // the first TCHAR in the array
(*pEnd)[1]; // the second TCHAR in the array

and another problem is that the language does not provide the mechanism
that would verify that there is the second TCHAR. Both of those should
lead you to the conclusion to use a regular pointer to TCHAR:

TCHAR *pEnd = tr.GetBuffer(st r.GetLength()) + str.GetLength() - 2;

(also, check with CString interface, 'GetBuffer' may require releasing
the buffer later, and holding onto a pointer from an object's internal
data may not be such a good idea).

V
--
Please remove capital 'A's when replying by e-mail
I do not respond to top-posted replies, please don't ask

**peter koch** · Sep 24 '08, 08:35 PM

Re: pointer-to-two-adjactend-chars

On 24 Sep., 18:53, ".rhavin grobert" <cl...@yahoo.de wrote:

this is m$ vc++, but the question itself is c++ specific...
>
TCHAR is a 'char' in non-unicode.
>
functions return...
TCHAR* CString::GetBuf fer(int);
int CString::GetLen ght(int);
_______________ _______________ ____________
>
// code:
>
CString str ="SomeStringWit hMoreThanOneTCh ar";
TCHAR *(pEnd[2]) = /* § */ str.GetBuffer(s tr.GetLength()) +
str.GetLength() - 2;
// in other words: a pointer to the second-last TCHAR is returned

It does not look like that to me. I do not know CString, but this
looks like a runaway buffer.

_______________ _______________ ____________
>
in the place marked "/* § */", a cast is neccesary. My problem: i dont
find the correct syntax.
the error given is "cannot convert from 'char *' to 'char *[2]' ", but
inserting
>
(char *[2]), (char (*[2])), ((char*) [2]) or (*(char[2])) doesnt work.
Anyone knows the correct syntax for a cast to a pointer-to-two-
adjactend-TCHARs please?

You can't without a cast, but does it matter? If you used a char* (I
am surprised you don't use a char const*), char[0] points to the
second last character and char[1] to the last (assuming that your code
is correct, of course).

/Peter

**gw7rib@aol.com** · Sep 24 '08, 08:45 PM

Re: pointer-to-two-adjactend-chars

On 24 Sep, 17:53, ".rhavin grobert" <cl...@yahoo.de wrote:

this is m$ vc++, but the question itself is c++ specific...
>
TCHAR is a 'char' in non-unicode.
>
functions return...
TCHAR* CString::GetBuf fer(int);
int CString::GetLen ght(int);
_______________ _______________ ____________
>
// code:
>
CString str ="SomeStringWit hMoreThanOneTCh ar";
TCHAR *(pEnd[2]) = /* § */ str.GetBuffer(s tr.GetLength()) +
str.GetLength() - 2;
// in other words: a pointer to the second-last TCHAR is returned
_______________ _______________ ____________
>
in the place marked "/* § */", a cast is neccesary. My problem: i dont
find the correct syntax.
the error given is "cannot convert from 'char *' to 'char *[2]' ", but
inserting
>
(char *[2]), (char (*[2])), ((char*) [2]) or (*(char[2])) doesnt work.
Anyone knows the correct syntax for a cast to a pointer-to-two-
adjactend-TCHARs please?

Is there some reason why you need a pointer to two TCHARs? Can't you
make do with a pointer to the first one, and look at the next location
to find the second one when you need it?

I mean in a similar way to the the way strings are handled in C. You
don't actually have a pointer to the "whole string", you (normally)
have just a pointer to the first character of it. But from this
pointer you can find the second, third etc characters when you need
them.

Incidentally, your code looks odd, using chars in some places and
TCHARs in others. I'm not sure what use this is. If the code is being
written purely for non-Unicode, then there seems no reason to use
TCHARs at all. Whereas, if the code might one day be used with
Unicode, you would find it convenient to have it all set up that way -
which would require adding "_TEXT"s and the like to your code.

Hope that helps.
Paul.

pointer-to-two-adjactend-chars

pointer-to-two-adjactend-chars

Comment

Comment

Comment