Binary constant macros

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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

Re: Binary constant macros
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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.

--
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   Available for consulting/temporary embedded and systems.
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Re: Binary constant macros
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<snip>

Very good!

Regards
Sergio Masci

http://www.xcprod.com/titan/XCSB - optimising structured PIC BASIC compiler



Re: Binary constant macros

[whatever = B8(10101010); using long hex constants}

really clever, thanks!

Oliver
--
Oliver Betz, Muenchen

Re: Binary constant macros
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Sweet and evil. I like it.

pete
--
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Re: Binary constant macros
On Fri, 27 Feb 2004 20:59:22 +0000, the renowned Pete Fenelon

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

Best regards,
Spehro Pefhany
--
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Re: Binary constant macros

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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
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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

Re: Binary constant macros
Between this and the URL of the unmaintainable code site it has been a
glorious day for comp.arch.embedded!  Thanks, Tom.  Your contribution has
already enhanced my current project!

--
========================================================================
          Michael Kesti            |  "And like, one and one don't make
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Re: Binary constant macros


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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


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