Store a pointer inside a dword data structure

[engine]

Hi.

I am working with data structures that have pointers to strings and dwords. Something like this:

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So a dword is by definition an unsigned 32 bit integer. Under my observations a pointer seems to be an unsigned integer. My problem is that I don't know if the length of a pointer fits inside a 32 bit length. If true a dword could store a pointer.

Any help is appreciated.

[martin]

I don't think you will have a problem with that untill you get on a 64 bit OS where pointers are obviously 64 bit.

[engine]

Thanks.

So on 32 bit OS, pointers are 32 bit. On 64 bit OS, pointers are 64 bit. Correct?

OK. I want my functions to work on the greatest number of OS possible. So I will think about another solution.

[cppman]

Thanks.

So on 32 bit OS, pointers are 32 bit. On 64 bit OS, pointers are 64 bit. Correct?

OK. I want my functions to work on the greatest number of OS possible. So I will think about another solution.

Yes. But you can also store a 32 bit pointer in a 64 bit data type.

32-bit pointer.

char *mystring = "hello world";
DWORD address = (DWORD)mystring; //address now stores the numeric memory address of my variable, mystring.

64-bit pointer (using this will work on both 32-bit systems and 64-bit systems)

char *mystring = "hello world";
__int64 address = (__int64)mystring; //same thing..

Both work. The second code will also work on 64 bit processors.

Edited August 12, 2008 by cppman

[engine]

In AutoIt documentation it's written under "DllStructCreate":

ptr 32bit(4bytes) integer

also

int_ptr 32 or 64bit signed integer (depending on if the x86 or x64 version of AutoIt is used)

So, should I use "ptr" or "int_ptr"?

[engine]

Yes. But you can also store a 32 bit pointer in a 64 bit data type.

32-bit pointer.

char *mystring = "hello world";
DWORD address = (DWORD)mystring; //address now stores the numeric memory address of my variable, mystring.

64-bit pointer (using this will work on both 32-bit systems and 64-bit systems)

char *mystring = "hello world";
__int64 address = (__int64)mystring; //same thing..

Both work. The second code will also work on 64 bit processors.

Thanks.

Unfortunately that wont work on my case. I am reading an existing byte data structure that consists on structures like the ones I mentioned above. So the pointer 32 bit or 64 bit is already defined on that byte data structure.

Regards.

[cppman]

In AutoIt documentation it's written under "DllStructCreate":

also

So, should I use "ptr" or "int_ptr"?

But use an unsigned one (or a "ulong_ptr", they are the same thing).

[cppman]

Thanks.

Unfortunately that wont work on my case. I am reading an existing byte data structure that consists on structures like the ones I mentioned above. So the pointer 32 bit or 64 bit is already defined on that byte data structure.

Regards.

I'm confused. It that doesn't work, why would it work if you were to use "ulong_ptr"? A DWORD is 32 bits. An __int64 is 64 bits. If the pointer inside the struct is all ready a 32 bit pointer, you can still assign that pointer to a 64 bit data type (an __int64).

Just think of a pointer as a number (that's all it is).

The maximum number a 32 bit pointer can hold is: 4,294,967,295 (that's why the maximum amount of memory on a 32-bit processor is 4GB)

The maximum number a 64 bit pointer can hold is: 18,446,744,073,709,551,615

Edited August 13, 2008 by cppman

[engine]

I'm confused. It that doesn't work, why would it work if you were to use "ulong_ptr"? A DWORD is 32 bits. An __int64 is 64 bits. If the pointer inside the struct is all ready a 32 bit pointer, you can still assign that pointer to a 64 bit data type (an __int64).

I am sorry. It would take too long to explain it properly.

It just doesn't work.

[engine]

Thanks cppman.

There is a topic on that -> http://www.autoitscript.com/forum/index.ph...=56168&st=0

The AutoIt include "Structures.au3" is using "ptr" so I am sticking to it.

[engine]

I'm confused. It that doesn't work, why would it work if you were to use "ulong_ptr"? A DWORD is 32 bits. An __int64 is 64 bits. If the pointer inside the struct is all ready a 32 bit pointer, you can still assign that pointer to a 64 bit data type (an __int64).

Just think of a pointer as a number (that's all it is).

The maximum number a 32 bit pointer can hold is: 4,294,967,295 (that's why the maximum amount of memory on a 32-bit processor is 4GB)

The maximum number a 64 bit pointer can hold is: 18,446,744,073,709,551,615

Actually "ulong_ptr" works, "uint64" doesn't.

I guess i can use "ulong_ptr" or "uint_ptr". They are the same, right?

[cppman]

Actually "ulong_ptr" works, "uint64" doesn't.

I guess i can use "ulong_ptr" or "uint_ptr". They are the same, right?

Yeah, they are both either 32 or 64 bits.

As for it not working, I'm not sure why. You can store a 32-bit pointer inside a 64-bit integer.

Edited August 13, 2008 by cppman