Binary constant macros

[Tom Torfs]

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

 

[CBFalconer]

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.

 

[Sergio Masci]

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

 

[Pete Fenelon]

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

 

[Leor Zolman]

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
(e-mail address removed)
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

 

[Spehro Pefhany]

Sweet and evil. I like it.

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

Best regards,
Spehro Pefhany

 

[Uwe Hercksen]

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