datatype for bit flags

From	Gr <g@g.com>
Newsgroups	comp.lang.c, comp.lang.c++
Subject	datatype for bit flags
Date	2011-09-15 12:37 +0530
Organization	A noiseless patient Spider
Message-ID	<j4s877$2a0$1@dont-email.me> (permalink)

Cross-posted to 2 groups.

Show all headers | View raw

I am not an expert C or C++ programmer but know enough to get by.

Currently studying some graphics algorithms as a part of CAD.

In the Cohen Sutherland Algorithm of line clipping, a code/flag is using 
for denoting where an endpoint of the line lies as compared to the 
clipping rectangle.

This code consists of 4 flags (1 each for left, right, below & above).

type code = 0;

if(point lies to the left of clipping window)
    code = code & 1;
if(point lies to right)
    code = code & 2;

if(point lies below)
   code = code & 4;
if(point lies above)
   code = code & 8;


Now in some books the type of code is declared
as
unsigned char code;
In others, it's
int code;

which is better?

unsigned char code saves space
(is the unsigned really necessary anyway?)

but I think int is probably faster.

Can someone explain what's a better way to do this if you were
writing a graphics library?

Back to comp.lang.c | Previous | Next — Next in thread | Find similar | Unroll thread

Thread

datatype for bit flags Gr <g@g.com> - 2011-09-15 12:37 +0530
  Re: datatype for bit flags jacob navia <jacob@spamsink.net> - 2011-09-15 09:26 +0200
    Re: datatype for bit flags Gr <g@g.com> - 2011-09-15 13:33 +0530
      Re: datatype for bit flags jacob navia <jacob@spamsink.net> - 2011-09-15 10:12 +0200
  Re: datatype for bit flags Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-09-15 01:06 -0700
  Re: datatype for bit flags "BartC" <bc@freeuk.com> - 2011-09-15 10:56 +0100
    Re: datatype for bit flags Gr <g@g.com> - 2011-09-15 17:24 +0530
  Re: datatype for bit flags Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2011-09-16 01:16 +0300
    Re: datatype for bit flags Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-09-16 04:59 -0700
      Re: datatype for bit flags Jorgen Grahn <grahn+nntp@snipabacken.se> - 2011-09-16 20:46 +0000
        Re: datatype for bit flags pete <pfiland@mindspring.com> - 2011-09-16 18:00 -0400
        Re: datatype for bit flags Malcolm McLean <malcolm.mclean5@btinternet.com> - 2011-09-18 05:00 -0700
          Re: datatype for bit flags Jorgen Grahn <grahn+nntp@snipabacken.se> - 2011-09-18 13:36 +0000
      Re: datatype for bit flags "Tony" <nospamme@ever.net> - 2011-09-16 16:47 -0500
        Re: datatype for bit flags pete <pfiland@mindspring.com> - 2011-09-16 18:35 -0400
          Re: datatype for bit flags Keith Thompson <kst-u@mib.org> - 2011-09-16 16:25 -0700
            Re: datatype for bit flags pete <pfiland@mindspring.com> - 2011-09-17 02:35 -0400
              Re: datatype for bit flags Keith Thompson <kst-u@mib.org> - 2011-09-17 14:42 -0700
          Re: datatype for bit flags "Tony" <nospamme@ever.net> - 2011-09-16 19:27 -0500
  Re: datatype for bit flags hanukas <jukka@liimatta.org> - 2011-09-23 03:56 -0700

csiph-web