How to cast an specified type pointer to integer?

[Allen]

I want to package an address to byte buffer. So I need to cast it to
integer value.
How to cast it?

const char * ptr = 0x0013e328;
int value = <cast(ptr); // use reinterpret_cas t?

[Ian Collins]

Allen wrote:

I want to package an address to byte buffer. So I need to cast it to
integer value.

Why? Surely if you are putting it in a byte buffer, you want a pointer?

--
Ian Collins.

[Allen]

On 1ÔÂ30ÈÕ, ÏÂÎç4ʱ12·Ö, Ian Collins <[e-mail] mwrote:

Allen wrote:

I want to package an address to byte buffer. So I need to cast it to
integer value.

Why? Surely if you are putting it in a byte buffer, you want a pointer?

--
Ian Collins.

Yes.
I package RPC output parameter to a byte buffer. So I need to remember
the output variable address.
How to do it?

[Ondra Holub]

Allen napsal:

I want to package an address to byte buffer. So I need to cast it to
integer value.
How to cast it?

const char * ptr = 0x0013e328;
int value = <cast(ptr); // use reinterpret_cas t?

Yes, use reinterpret_cas t. Or you can use union

union Cast
{
const char* szptr;
const int* iptr;
};

In both cases are you taking the responsibility for this conversion
(you claim you know how is it stored there). But for casting pointers
there should be no problem.

[Allen]

On 1ÔÂ30ÈÕ, ÏÂÎç4ʱ18·Ö, "Ondra Holub" <ondra.ho...@po st.czwrote:

Allen napsal:

I want to package an address to byte buffer. So I need to cast it to
integer value.
How to cast it?

const char * ptr = 0x0013e328;
int value = <cast(ptr); // use reinterpret_cas t?

Yes, use reinterpret_cas t. Or you can use union

union Cast
{
const char* szptr;
const int* iptr;

};

In both cases are you taking the responsibility for this conversion
(you claim you know how is it stored there). But for casting pointers
there should be no problem.

I do like this:
int address =
reinterpret_cas t<int>(reinterp ret_cast<int*>( const_cast<char *>((ptr))))
;

But the compiler gives a warning, warning C4311: "reinterpret_ca st":
from int* to int pointer cut off.

[Ondra Holub]

Allen napsal:

On 1ÔÂ30ÈÕ, ÏÂÎç4ʱ18·Ö, "Ondra Holub" <ondra.ho....@p ost.czwrote:

Allen napsal:

I want to package an address to byte buffer. So I need to cast it to
integer value.
How to cast it?

const char * ptr = 0x0013e328;
int value = <cast(ptr); // use reinterpret_cas t?

Yes, use reinterpret_cas t. Or you can use union

union Cast
{
const char* szptr;
const int* iptr;

};

In both cases are you taking the responsibility for this conversion
(you claim you know how is it stored there). But for casting pointers
there should be no problem.

I do like this:
int address =
reinterpret_cas t<int>(reinterp ret_cast<int*>( const_cast<char *>((ptr))))
;

But the compiler gives a warning, warning C4311: "reinterpret_ca st":
from int* to int pointer cut off.

I see you are trying to assign pointer value to int. It is not good
idea. It is quite common, that pointer does not fit into int value
(for example on 64-bits systems). That's the reason for such warning.

[Jacek Dziedzic]

Allen wrote:

I want to package an address to byte buffer. So I need to cast it to
integer value.

Why an integer? What if a pointer does not fit into
an integer? On my system
sizeof(void*)== 8, sizeof(int)==4, what then?

I would try pointing a char* pointer to the
pointer in question (not to the address!) and
then read subsequent char's, incrementing the
pointer and storing them into a vector<char>
that would be sizeof(void*) elements long.

HTH,
- J.

[Dave Rahardja]

On Tue, 30 Jan 2007 09:54:30 +0100, Jacek Dziedzic
<ja************ ************@gm ail.comwrote:

>Allen wrote:

>I want to package an address to byte buffer. So I need to cast it to
integer value.

Why an integer? What if a pointer does not fit into
an integer? On my system
sizeof(void*)= =8, sizeof(int)==4, what then?

I would try pointing a char* pointer to the
pointer in question (not to the address!) and
then read subsequent char's, incrementing the
pointer and storing them into a vector<char>
that would be sizeof(void*) elements long.

I suspect the OP is dealing with some I/O protocol that specifies a certain
number of bytes for pointer types, regardless of platform.

OP: This is very low level code and you'd better know what you're doing. It
helps to do the following as well:

#include "boost/static_assert.h pp"

BOOST_STATIC_AS SERT(sizeof(voi d*) <= sizeof(int));

See boost.org for the boost library.

-dr

[Ivan Novick]

On Jan 30, 12:29 am, "Allen" <che...@naritec h.cnwrote:

I do like this:
int address =
reinterpret_cas t<int>(reinterp ret_cast<int*>( const_cast<char *>((ptr))))
;

But the compiler gives a warning, warning C4311: "reinterpret_ca st":
from int* to int pointer cut off.- Hide quoted text -

Yes, like the other poster said, the sizeof int on your system may not
be big enough to hold a pointer value. reinterpret_cas t is definitely
the right way to cast it. Instead of putting the result into an int,
you can use intptr_t which is guaranteed to be a typedef to an integer
type big enough to hold a pointer on your system. intptr_t is not
part of the C++ standard, but I believe it is part of the C standard,
and is available in g++, and may even be in the queue to be added to
the C++ standard in the future.

Ivan
http://www.0x4849.net

[Sylvester Hesp]

"Ivan Novick" <iv***********@ gmail.comwrote in message
news:11******** **************@ v33g2000cwv.goo glegroups.com.. .

On Jan 30, 12:29 am, "Allen" <che...@naritec h.cnwrote:

>I do like this:
int address =
reinterpret_ca st<int>(reinter pret_cast<int*> (const_cast<cha r*>((ptr))))
;

But the compiler gives a warning, warning C4311: "reinterpret_ca st":
from int* to int pointer cut off.- Hide quoted text -

Yes, like the other poster said, the sizeof int on your system may not
be big enough to hold a pointer value. reinterpret_cas t is definitely
the right way to cast it. Instead of putting the result into an int,
you can use intptr_t which is guaranteed to be a typedef to an integer
type big enough to hold a pointer on your system. intptr_t is not
part of the C++ standard, but I believe it is part of the C standard,
and is available in g++, and may even be in the queue to be added to
the C++ standard in the future.

Ivan
http://www.0x4849.net

-----code-----------------------------------------------
#include <cstddef>

template<intstr uct intselector;
template<struct intselector<1>
{ typedef unsigned char type; };
template<struct intselector<2>
{ typedef unsigned short type; };
template<struct intselector<3>
{ typedef unsigned int type; };
template<struct intselector<4>
{ typedef unsigned long type; };

// and if your platform supports it (non-standard):
//template<struct intselector<5>
// { typedef unsigned long long type; };

template<size_t Sstruct inttype
{
typedef typename intselector
<
S <= sizeof(unsigned char)
? 1
: S <= sizeof(unsigned short)
? 2
: S <= sizeof(unsigned int)
? 3
: S <= sizeof(unsigned long)
? 4
: 5

>::type type;

};

typedef inttype<sizeof( void*)>::type intptr_t;
-----end code-------------------------------------------
Now you have an intptr_t on every platform ;)

- Sylvester