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

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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: 20761
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: 20761
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

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