Re: A89: Filling a Byte in C

To: Assembly 89 List <assembly-89@lists.ticalc.org>
Subject: Re: A89: Filling a Byte in C
From: Patrick Davidson <pad@ocf.Berkeley.EDU>
Date: Sun, 14 May 2000 20:00:38 -0700 (PDT)
In-Reply-To: <001001bfbe17$755fc880$58ec5c18@twcny.rr.com>
Reply-To: assembly-89@lists.ticalc.org




On Sun, 14 May 2000, Sebastian Reichelt wrote:

> 
> Hi,
> 
> does anyone know how to fill a byte from bit x to bit y with ones in C, and
> fill the rest with zeros.  Here's my solution, but I'm sure there is a much
> better way:

I'm not sure if this way is better, but it is certainly smaller:

char GetByteMask(char start, char end)
{
    char x = 0;
    int y;
    for (y = start; y <= end; y++)
        x |= 1 << y;
    return x;
}

In case you can't guess:

x |= y      means set X to X logical or Y
x << y      means shift x left y bits (multiply x by 2^y)

Follow-Ups:

Re: A89: Filling a Byte in C

From: "mheckenbach" <mheckenbach@yahoo.com>

References:

A89: Filling a Byte in C

From: "Sebastian Reichelt" <SebastianR@gmx.de>