×
INTELLIGENT WORK FORUMS
FOR COMPUTER PROFESSIONALS

Log In

Come Join Us!

Are you a
Computer / IT professional?
Join Tek-Tips Forums!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

*Tek-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

Students Click Here

ASM typecasting

ASM typecasting

ASM typecasting

(OP)
I've been able to get back into the assembler a bit more for various reasons.  Anyhow, I'm still learning and I found something I would like some advice on.

CODE

crc32_out := CRC32tab[Byte(crc32_out xor DWord(PChar(inbuffer)^))] xor
                    ((crc32_out shr 8) and $00ffffff);

In converting this Pascal code, the thing I struggled with was the typecasting parts.  Now I'm fine with the DWord typecast for most part ( XOR E?X, E?X then move byte to ?L ).  

Now the Byte typecast was a little bit more trouble because I needed the lower byte of that result ( ?L ) to address the array represented by CRC32tab.  I figured it out by using 3 or 4 instructions to clear the high 24-bits of the extended register.

But the question is this: Is there a better way to approach this problem?  

It is not possible for anyone to acknowledge truth when their salary depends on them not doing it.

RE: ASM typecasting

(OP)
But the question is this: Is there a better way to approach this problem?   

Got this answered.  Needed the MOVZX instruction.

It is not possible for anyone to acknowledge truth when their salary depends on them not doing it.

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Tek-Tips Forums free from inappropriate posts.
The Tek-Tips staff will check this out and take appropriate action.

Reply To This Thread

Posting in the Tek-Tips forums is a member-only feature.

Click Here to join Tek-Tips and talk with other members! Already a Member? Login

Close Box

Join Tek-Tips® Today!

Join your peers on the Internet's largest technical computer professional community.
It's easy to join and it's free.

Here's Why Members Love Tek-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close