C RSS C RSS

Problem with Bitwise Masking

Reply

•
•
Join Date: Sep 2009
Posts: 17
Reputation: Kombat is an unknown quantity at this point 
Solved Threads: 0
Kombat Kombat is offline Offline
Newbie Poster

Problem with Bitwise Masking

 
0
  #1
17 Days Ago
Ok so I make my masks
C Syntax (Toggle Plain Text) 
  1. short m1, m2, m3, m4;
  2.  
  3. m1 = 0xF000;
  4. m2 = 0x0F00;
  5. m2 = 0x00F0;
  6. m3 = 0x000F;

and then I test my masks
C Syntax (Toggle Plain Text) 
  1. printf("%hd %hd %hd %hd\n", m1, m2, m3, m4);

when I test it the values come out as
C Syntax (Toggle Plain Text) 
  1. -4096 240 15 0

which is equal to

C Syntax (Toggle Plain Text) 
  1. 0xF000
  2. 0x00F0
  3. 0x000F
  4. 0x0000

which is messing up my checksum program when I try to apply the masks. :-\

Any advice?
Reply With Quote Quick reply to this message  
•
•
Join Date: Jan 2008
Posts: 346
Reputation: gerard4143 is on a distinguished road 
Solved Threads: 44
gerard4143's Avatar
gerard4143 gerard4143 is online now Online
Posting Whiz
 
0
  #2
17 Days Ago
•
•
•
•
Originally Posted by Kombat View Post
Ok so I make my masks
C Syntax (Toggle Plain Text) 
  1. short m1, m2, m3, m4;
  2.  
  3. m1 = 0xF000;
  4. m2 = 0x0F00;
  5. m2 = 0x00F0;
  6. m3 = 0x000F;

and then I test my masks
C Syntax (Toggle Plain Text) 
  1. printf("%hd %hd %hd %hd\n", m1, m2, m3, m4);

when I test it the values come out as
C Syntax (Toggle Plain Text) 
  1. -4096 240 15 0

which is equal to

C Syntax (Toggle Plain Text) 
  1. 0xF000
  2. 0x00F0
  3. 0x000F
  4. 0x0000

which is messing up my checksum program when I try to apply the masks. :-\

Any advice?

I tried initializing the values like this and it worked

C Syntax (Toggle Plain Text) 
  1. #include <stdio.h>
  2. #include <stdlib.h>
  3.  
  4. int main(int argc, char**argv)
  5. {
  6.  
  7. short m1 = 0xf000, m2 = 0x0f00, m3 = 0x00f0, m4 = 0x000f;
  8.  
  9. printf("%hd %hd %hd %hd\n", m1, m2, m3, m4);
  10.  
  11. exit(EXIT_SUCCESS);
  12. }

What are you using for a compiler?
Last edited by gerard4143; 17 Days Ago at 2:14 pm.
Reply With Quote Quick reply to this message  
•
•
Join Date: Sep 2009
Posts: 17
Reputation: Kombat is an unknown quantity at this point 
Solved Threads: 0
Kombat Kombat is offline Offline
Newbie Poster
 
0
  #3
17 Days Ago
gcc on a unix machine
Reply With Quote Quick reply to this message  
•
•
Join Date: Apr 2004
Posts: 4,335
Reputation: Dave Sinkula has a brilliant future Dave Sinkula has a brilliant future Dave Sinkula has a brilliant future Dave Sinkula has a brilliant future Dave Sinkula has a brilliant future Dave Sinkula has a brilliant future Dave Sinkula has a brilliant future Dave Sinkula has a brilliant future Dave Sinkula has a brilliant future Dave Sinkula has a brilliant future Dave Sinkula has a brilliant future 
Solved Threads: 236
Team Colleague
Dave Sinkula's Avatar
Dave Sinkula Dave Sinkula is offline Offline
long time no c
 
0
  #4
17 Days Ago
Used unsigned integral types when dealing with bits.

C Syntax (Toggle Plain Text) 
  1. #include <stdio.h>
  2. #include <stdlib.h>
  3.  
  4. int main()
  5. {
  6.    unsigned short m1 = 0xf000, m2 = 0x0f00, m3 = 0x00f0, m4 = 0x000f;
  7.    printf("%hu %hu %hu %hu\n", m1, m2, m3, m4);
  8.    printf("%hx %hx %hx %hx\n", m1, m2, m3, m4);
  9.    return 0;
  10. }
  11.  
  12. /* my output
  13. 61440 3840 240 15
  14. f000 f00 f0 f
  15. */
[edit]Part of the reason for your "strange" output:
•
•
•
•
Originally Posted by Kombat View Post
Ok so I make my masks 
short m1, m2, m3, m4;

m1 = 0xF000;
m2 = 0x0F00;
m2 = 0x00F0;
m3 = 0x000F;
You don't give m4 a value.
Last edited by Dave Sinkula; 17 Days Ago at 2:45 pm.
"One of the methods used by statists to destroy capitalism consists in establishing controls that tie a given industry hand and foot, making it unable to solve its problems, then declaring that freedom has failed and stronger controls are necessary." --Ayn Rand
Reply With Quote Quick reply to this message  
Reply

Quick Reply to Thread
•
•
•
•
•
•
•
•
Message:
•
•
•
•



Similar Threads
Other Threads in the C Forum
Thread Tools Search this Thread



* adobe ansi api array arrays binarysearch calculate centimeter char cm convert copyanyfile copypdffile cprogramme createcopyoffile createprocess() csyntax directory dynamic feet fflush file floatingpointvalidation fork forloop frequency getlasterror getlogicaldrivestrin givemetehcodez global graphics gtkgcurlcompiling gtkwinlinux hacking hardware highest homework i/o inches incrementoperators intmain() iso km linked linkedlist linux linuxsegmentationfault list locate logical_drives loopinsideloop. match matrix microsoft motherboard mqqueue mysql oddnumber odf open opendocumentformat openwebfoundation pattern pdf performance pointer posix power program programming pyramidusingturboccodes read recursion recv recvblocked repetition reversing scanf scheduling segmentationfault send shape single socketprograming socketprogramming stack standard strchr string suggestions test unix urboc user variable voidmain() whythiscodecausesegmentationfault win32api windows.h
About Us | Contact Us | Advertise | DaniWeb | Acceptable Use Policy | RSS Feed

©2003 - 2009 DaniWeb® LLC