Don't worry about the assembler code - that just sets and gets the bits.
Looking in the source for TBits.SetSize we see
NewMemSize := ((Value + BitsPerInt - 1) div BitsPerInt) * SizeOf(Integer);
where BitsPerInt = BitsPerInt = SizeOf(Integer) * 8;
Sizeof(Integer) = 4 on my system, so BitsPerInt = 32.
NewMemSize is the number of bytes used in the GetMem function.
For a TBits size of say 10, we get
NewMemSize = ( (10+32-1) div 32) * 4
= (41 div 32) * 4
= 4 bytes
For size = 100 we allocate (131 div 32) * 4 = 16 bytes.
Not bad memory use. There is also an overhead of 1 Integer for Size and 1
pointer to the Bits array.
Wes Edwards
> -----Original Message-----
> From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED]]On
> Behalf Of Nahum Wild
> Sent: Friday, 15 December 2000 13:06
> To: Multiple recipients of list delphi
> Subject: [DUG]: TBits - array of bits
>
>
> I'm wanting to create a 2d array of bits where the less memory
> used to store
> the array the better. A boolean array is out of the question as a boolean
> uses up a byte. So I looked in the D5 help and found the TBits class. It
> is accessed as a boolean but looking at its source code reveals that its
> coded in assembler. Which I can't read. So my question is - does TBits
> store everything at the bit level or at the byte level?
>
> Alternatively does anyone know of a different approach to doing this where
> memory footprint it critical with access speed coming a close second?
>
>
> Cheers,
>
> Nahum Wild
> Game Designer
> Realism Ltd
>
> ESDAO - The wargame of a thousand faces.
> http://www.esdao.net
>
> Download the public beta version now!
>
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