What about this line?

[Gaudalier]

Hi there!
I'm coding a function from C to asm.

I need to know how much memory does Allocate the next c line:

//typedef struct { BYTE X,Y,W,H; } offsetPOS;
//offsetPOS *POS_buffer;
nControls=100
POS_buffer=(offsetPOS *)(malloc(nControls))

How many byte is allocated at POS_Buffer? 400?

Can you enligh me a bit from "(offsetPOS *)" ???

Thanks

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http://www.carabez.com

 

[ArkM]

nControls = 100; // semicolon?

100 (one hundred, or 10*10 in decimals), of course. What's a problem?..

 

[Gaudalier]

I'm traslating this C code to Assembler code:

POS_buffer=(offsetPOS *)(malloc(nControls))

Ok, Malloc parameter = number of contiguous bytes of storage to be allocated, 100 indicated by nControls.

What I dunno is "(offsetPOS *)":

It's mean to be size of offsetPOS (4) times malloc(100)) = 400 contiguous bytes???



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http://www.carabez.com

 

[SamBones]

The way I see it...

1) [tt]offsetPOS[/tt] is a structure.
2) [tt]POS_buffer[/tt] is a pointer to an [tt]offsetPOS[/tt] structure.
3) [tt]nControls[/tt] is a variable (I assume type [tt]size_t[/tt]) that's being set to 100.
4) The [tt]malloc(nControls)[/tt] is allocating some memory 100 bytes long (because [tt]nControls[/tt] = 100), and it returns the address of the memory.
5) The [tt](offsetPOS *)[/tt] is casting that memory address returned by the [tt]malloc[/tt] to the type "pointer to an [tt]offsetPOS[/tt] structure".
6) The variable [tt]POS_buffer[/tt] ends up holding that value.

Hope this helps.

 

[Gaudalier]

Wow!

Hey SamBones, That code is now Cristal Clear!!!!!

Thank Ya, very much!

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http://www.carabez.com

 

[SamBones]

Yeah, the asterisk ([tt]*[/tt]) in this case is indicating a "pointer", not multiplication.

Hope this helps.