By using this site, you agree to our updated Privacy Policy and our Terms of Use. Manage your Cookies Settings.
464,271 Members | 1,294 Online
Bytes IT Community
+ Ask a Question
Need help? Post your question and get tips & solutions from a community of 464,271 IT Pros & Developers. It's quick & easy.

Binary constant macros

P: n/a
Hello All,

I've been missing the lack of support for binary numeric literals in
C. To get around it I wrote the following handy macros, which allows
you to simply write something like:

whatever = B8(10101010);

and will translate as:

whatever = 85;

(compile-time constant)

Code below... hopefully it's useful to some of you as well.

greetings,
Tom

/* Binary constant generator macro
By Tom Torfs - donated to the public domain
*/

/* All macro's evaluate to compile-time constants */

/* *** helper macros *** /

/* turn a numeric literal into a hex constant
(avoids problems with leading zeroes)
8-bit constants max value 0x11111111, always fits in unsigned long
*/
#define HEX__(n) 0x##n##LU

/* 8-bit conversion function */
#define B8__(x) ((x&0x0000000FLU)?1:0) \
+((x&0x000000F0LU)?2:0) \
+((x&0x00000F00LU)?4:0) \
+((x&0x0000F000LU)?8:0) \
+((x&0x000F0000LU)?16:0) \
+((x&0x00F00000LU)?32:0) \
+((x&0x0F000000LU)?64:0) \
+((x&0xF0000000LU)?128:0)

/* *** user macros *** /

/* for upto 8-bit binary constants */
#define B8(d) ((unsigned char)B8__(HEX__(d)))

/* for upto 16-bit binary constants, MSB first */
#define B16(dmsb,dlsb) (((unsigned short)B8(dmsb)<<8) \
+ B8(dlsb))

/* for upto 32-bit binary constants, MSB first */
#define B32(dmsb,db2,db3,dlsb) (((unsigned long)B8(dmsb)<<24) \
+ ((unsigned long)B8(db2)<<16) \
+ ((unsigned long)B8(db3)<<8) \
+ B8(dlsb))

/* Sample usage:
B8(01010101) = 85
B16(10101010,01010101) = 43605
B32(10000000,11111111,10101010,01010101) = 2164238933
*/

greetings,
Tom
Nov 14 '05 #1
Share this Question
Share on Google+
6 Replies

P: n/a
Tom Torfs wrote:

I've been missing the lack of support for binary numeric literals
in C. To get around it I wrote the following handy macros, which
allows you to simply write something like:

whatever = B8(10101010);
.... snip ...
/* Sample usage:
B8(01010101) = 85
B16(10101010,01010101) = 43605
B32(10000000,11111111,10101010,01010101) = 2164238933
*/


That is rather cute. You should wrap the macro file in an include
guard. The comma separation on byte boundaries especially adds
clarity. It does have some portability problems outside the
normal world of 8 bit bytes and 16/32 bit short/longs.

--
Chuck F (cb********@yahoo.com) (cb********@worldnet.att.net)
Available for consulting/temporary embedded and systems.
<http://cbfalconer.home.att.net> USE worldnet address!
Nov 14 '05 #2

P: n/a
Tom Torfs <to******@village.uunet.be> wrote in message
news:b9**************************@posting.google.c om...
Hello All,

I've been missing the lack of support for binary numeric literals in
C. To get around it I wrote the following handy macros, which allows
you to simply write something like:

whatever = B8(10101010);

and will translate as:

whatever = 85;

(compile-time constant)

Code below... hopefully it's useful to some of you as well.

greetings,
Tom


<snip>

Very good!

Regards
Sergio Masci

http://www.xcprod.com/titan/XCSB - optimising structured PIC BASIC compiler
Nov 14 '05 #3

P: n/a
In comp.arch.embedded Tom Torfs <to******@village.uunet.be> wrote:
Hello All,

I've been missing the lack of support for binary numeric literals in
C. To get around it I wrote the following handy macros, which allows
you to simply write something like:


Sweet and evil. I like it.

pete
--
pe**@fenelon.com "there's no room for enigmas in built-up areas"
Nov 14 '05 #4

P: n/a
On 26 Feb 2004 07:36:35 -0800, to******@village.uunet.be (Tom Torfs) wrote:
Hello All,

I've been missing the lack of support for binary numeric literals in
C. To get around it I wrote the following handy macros, which allows
you to simply write something like:

whatever = B8(10101010);

and will translate as:

whatever = 85;

(compile-time constant)

Code below... hopefully it's useful to some of you as well.

greetings,
Tom

/* Binary constant generator macro
By Tom Torfs - donated to the public domain
*/

/* All macro's evaluate to compile-time constants */

/* *** helper macros *** /

/* turn a numeric literal into a hex constant
(avoids problems with leading zeroes)
8-bit constants max value 0x11111111, always fits in unsigned long
*/
#define HEX__(n) 0x##n##LU

/* 8-bit conversion function */
#define B8__(x) ((x&0x0000000FLU)?1:0) \
+((x&0x000000F0LU)?2:0) \
+((x&0x00000F00LU)?4:0) \
+((x&0x0000F000LU)?8:0) \
+((x&0x000F0000LU)?16:0) \
+((x&0x00F00000LU)?32:0) \
+((x&0x0F000000LU)?64:0) \
+((x&0xF0000000LU)?128:0)

/* *** user macros *** /

/* for upto 8-bit binary constants */
#define B8(d) ((unsigned char)B8__(HEX__(d)))

/* for upto 16-bit binary constants, MSB first */
#define B16(dmsb,dlsb) (((unsigned short)B8(dmsb)<<8) \
+ B8(dlsb))

/* for upto 32-bit binary constants, MSB first */
#define B32(dmsb,db2,db3,dlsb) (((unsigned long)B8(dmsb)<<24) \
+ ((unsigned long)B8(db2)<<16) \
+ ((unsigned long)B8(db3)<<8) \
+ B8(dlsb))

/* Sample usage:
B8(01010101) = 85
B16(10101010,01010101) = 43605
B32(10000000,11111111,10101010,01010101) = 2164238933
*/

greetings,
Tom


This may be closest thing I've seen to C++ template metaprogramming... in
C. And it doesn't even require the most up-to-date compilers! ;-)
Very useful.
-leor

Leor Zolman
BD Software
le**@bdsoft.com
www.bdsoft.com -- On-Site Training in C/C++, Java, Perl & Unix
C++ users: Download BD Software's free STL Error Message
Decryptor at www.bdsoft.com/tools/stlfilt.html
Nov 14 '05 #5

P: n/a
On Fri, 27 Feb 2004 20:59:22 +0000, the renowned Pete Fenelon
<pe**@fenelon.com> wrote:
In comp.arch.embedded Tom Torfs <to******@village.uunet.be> wrote:
Hello All,

I've been missing the lack of support for binary numeric literals in
C. To get around it I wrote the following handy macros, which allows
you to simply write something like:


Sweet and evil. I like it.


Me too. Suggest you write it up for Dr. Dobbs.

Best regards,
Spehro Pefhany
--
"it's the network..." "The Journey is the reward"
sp***@interlog.com Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog Info for designers: http://www.speff.com
Nov 14 '05 #6

P: n/a


Tom Torfs wrote:

I've been missing the lack of support for binary numeric literals in
C. To get around it I wrote the following handy macros, which allows
you to simply write something like:

whatever = B8(10101010);

and will translate as:

whatever = 85;

(compile-time constant)

Hello,

thanks a lot, very helpful and very ingenious.
I think you will even manage to define macros for numbers with neither
decimal base nor a power of two as base.
But what is the use of compile time constant with a base of seven or
twelve? I can imagine no example, but maybe somebody else can. ;-)

Bye

Nov 14 '05 #7

This discussion thread is closed

Replies have been disabled for this discussion.