[solved]how casting a *dword to *word works?

Index > High Level Languages > [solved]how casting a *dword to *word works?

Author

Thread

vivik

Joined: 29 Oct 2016
Posts: 671

vivik 22 Feb 2018, 20:34

I need to do something like this:

dword* pointer = (dword*)malloc(1024);
*pointer++ = 1;
*pointer++ = 4;
*(word)pointer++ = 1;
*(word)pointer++ = 2;
*(word)pointer++ = 3;
*(word)pointer++ = 4;

how?

Last edited by vivik on 25 Feb 2018, 06:16; edited 1 time in total

22 Feb 2018, 20:34

DimonSoft

Joined: 03 Mar 2010
Posts: 1228
Location: Belarus

DimonSoft 22 Feb 2018, 22:36

vivik wrote:

I need to do something like this:

dword* pointer = (dword*)malloc(1024);
*pointer++ = 1;
*pointer++ = 4;
*(word)pointer++ = 1;
*(word)pointer++ = 2;
*(word)pointer++ = 3;
*(word)pointer++ = 4;

how?

Since the question is asked in “High Level Languages” section of the forum, I’ll ask what language do you want to use.

22 Feb 2018, 22:36

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20299
Location: In your JS exploiting you and your system

revolution 23 Feb 2018, 00:10

dword == long I presume? And word == short?

I think a good way to see what your compiler does with that code it to build it and then debug/disassemble it to see what it is doing.

23 Feb 2018, 00:10

rugxulo

Joined: 09 Aug 2005
Posts: 2341
Location: Usono (aka, USA)

rugxulo 23 Feb 2018, 05:15

Perhaps union?

23 Feb 2018, 05:15

vivik

Joined: 29 Oct 2016
Posts: 671

vivik 23 Feb 2018, 06:29

This worked:

*(unsigned short*)g_texture_thumb_cursor = 0xF1F2;
g_texture_thumb_cursor = (DWORD*)((unsigned short*)g_texture_thumb_cursor + 1);

Not very readable, huh? Had to google "void pointer increment".

23 Feb 2018, 06:29

vivik

Joined: 29 Oct 2016
Posts: 671

vivik 23 Feb 2018, 06:46

I think I'll use these types:

https://msdn.microsoft.com/en-us/library/windows/desktop/aa383751(v=vs.85).aspx

BYTE
WORD
DWORD

INT8
INT16
INT32
UINT8
UINT16
UINT32

23 Feb 2018, 06:46

DimonSoft

Joined: 03 Mar 2010
Posts: 1228
Location: Belarus

DimonSoft 23 Feb 2018, 06:59

vivik wrote:

I think I'll use these types:

https://msdn.microsoft.com/en-us/library/windows/desktop/aa383751(v=vs.85).aspx

BYTE
WORD
DWORD

INT8
INT16
INT32
UINT8
UINT16
UINT32

Might not be a good idea in terms of portability.

23 Feb 2018, 06:59

revolution
When all else fails, read the source

Joined: 24 Aug 2004
Posts: 20299
Location: In your JS exploiting you and your system

revolution 23 Feb 2018, 07:13

vivik wrote:

This worked:

*(unsigned short*)g_texture_thumb_cursor = 0xF1F2;
g_texture_thumb_cursor = (DWORD*)((unsigned short*)g_texture_thumb_cursor + 1);

Not very readable, huh? Had to google "void pointer increment".

So your compiler need all that ugliness just to do this:

Code:

g_texture_thumb_cursor dw 0xF1F2,0

inc dword[g_texture_thumb_cursor]

Ugh.

23 Feb 2018, 07:13

vivik

Joined: 29 Oct 2016
Posts: 671

vivik 24 Feb 2018, 08:24

Actually, it's much more simple if I just use char*.

char* pointer = (char*)malloc(1024);

*(INT32*)pointer = 1;
pointer += 4;

*(INT32*)pointer = 2;
pointer += 4;

*(UINT16*)pointer = 1;
pointer += 2;
*(UINT16*)pointer = 2;
pointer += 2;
*(UINT16*)pointer = 3;
pointer += 2;
*(UINT16*)pointer = 4;
pointer += 2;

24 Feb 2018, 08:24

DimonSoft

Joined: 03 Mar 2010
Posts: 1228
Location: Belarus

DimonSoft 24 Feb 2018, 09:39

vivik wrote:

Actually, it's much more simple if I just use char*.

char* pointer = (char*)malloc(1024);

*(INT32*)pointer = 1;
pointer += 4;

*(INT32*)pointer = 2;
pointer += 4;

*(UINT16*)pointer = 1;
pointer += 2;
*(UINT16*)pointer = 2;
pointer += 2;
*(UINT16*)pointer = 3;
pointer += 2;
*(UINT16*)pointer = 4;
pointer += 2;

Why not define a struct and cast the pointer?

24 Feb 2018, 09:39

vivik

Joined: 29 Oct 2016
Posts: 671

vivik 24 Feb 2018, 13:45

>Why not define a struct and cast the pointer?

Indeed why... I can merge the last four UINT16 into one struct at least. (Can't make everything into one structure, because the second INT32 is the amount of those UINT16.)

I need to compare the assembly, later.

24 Feb 2018, 13:45

< Last Thread | Next Thread >

Forum Rules:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum