Sender:	"Rolf Campbell" <cp1v45 AT nortelnetworks DOT com>
Message-ID:	<37C556A2.C1A89379@NortelNetworks.com>
Date:	Thu, 26 Aug 1999 11:00:51 -0400
From:	"Rolf Campbell" <cp1v45 AT nortelnetworks DOT com>
Organization:	Nortel Networks
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Newsgroups:	comp.os.msdos.djgpp
To:	djgpp AT delorie DOT com
Subject:	Re: Struct Array Allocation, Line Pointers, Automatic Offseting?
References:	<199908260412 DOT AAA09411 AT delorie DOT com>
Reply-To:	djgpp AT delorie DOT com

Dan Gold wrote:

> I made an 1 dimensional array of a struct and made line pointers to the
> start of each row to make it like a 2 dimensional array.  If I want to
> reference the line pointer as ->line[4][5], it will start on the row index
> 4, but will the 5 jump 5 tiles structs ahead as I allocated or just bytes.
> This is simalar to Allegro's bitmap line pointers which jump ahead bytes,
> but I am using structures not bytes.

If you declared it as a 'struct ... *' then it will jump in sizeof(struct)
bytes.

> If it does jump ahead structs for me, is there any speed concern when
> multiplying the address location 5 times by the size of the struct? [4th
> row] + [5 * sizeof TILE]

    Multiplying by 5 is not difficult, and can be done in 1 instruction
without any explicit multiply.  I don't remember the syntax.  Don't worry
about it.

> One more thing.  Does a struct pointer equal one 32bit address or an
> address for each member of the struct?

    It is just 1 32-bit address.

--
     -Rolf Campbell (39)3-6318

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