NetNews Offline 2/NetNews Offline Volume 2.iso/news/comp/lang/c-part1/5849

Text File | 1996-08-05 | 1.7 KB | 50 lines

Path: mail2news.demon.co.uk!genesis.demon.co.uk
From: Lawrence Kirby <[e-mail]>
Newsgroups: comp.lang.c
Subject: Re: Help With Pointers
Date: Wed, 21 Feb 96 14:45:02 GMT
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References: <4g67cj$[e-mail]>
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In article <4g67cj$[e-mail]>
           [e-mail] "Barry A. Ryan" writes:

>Hi
>
>Is there any way to assign a char pointer to a float pointer?

This is generally dangerous for alignment reasons - it is a much better
idea to assign a float pointer to a char pointer.

>I had to do some byte rotation on binary data.  I rotated
>the characters and know want to point a float at the first
>character position to read back a 4 byte float.

Consider:

    float value;
    char *ptr = (char *) &value;

You can now consider ptr as pointing to the first element of an array of
chars indexed from 0 to sizeof(float)-1.

>I'am actually trying to read SGI binary data with a PC.  I've been told
>that the SGI bytes ( not bits ) are rotated versus a PC.  Any help
>would be appreciated. Are the bytes rotated?

I don't know for certain but most likely the byte order is simply reversed
(big-endian vs. little endian) assuming that they are otherwise compatible.
Using the pointer set up above it would be very easy to copy the bytes
into the target float in the order you require.

--
-----------------------------------------
Lawrence Kirby | [e-mail]
Wilts, England | [e-mail]
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