bithacks.h

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/* 
** bithacks.h - bit hacks macros. v1.0
**
** Peteris Krumins (peter@catonmat.net)
** http://www.catonmat.net  --  good coders code, great reuse
**
** This file is explained in the following article:
** http://www.catonmat.net/blog/bit-hacks-header-file
**
** Released under the MIT license.
*/

#ifndef BITHACKS_H
#define BITHACKS_H

#define HEXIFY(x) 0x##x##LU

#define B8IFY(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))

#define B8(x) ((unsigned char)B8IFY(HEXIFY(x)))

/*
** Bit hack routines. See the following article for explanation:
** http://www.catonmat.net/blog/low-level-bit-hacks-you-absolutely-must-know
**
*/

/* test if x is even */
#define B_EVEN(x)        (((x)&1)==0)

/* test if x is odd */
#define B_ODD(x)         (!B_EVEN((x)))

/* test if n-th bit in x is set */
#define B_IS_SET(x, n)   (((x) & (1<<(n)))?1:0)

/* set n-th bit in x */
#define B_SET(x, n)      ((x) |= (1<<(n)))

/* unset n-th bit in x */
#define B_UNSET(x, n)    ((x) &= ~(1<<(n)))

/* toggle n-th bit in x */
#define B_TOGGLE(x, n)   ((x) ^= (1<<(n)))

/* turn off right-most 1-bit in x */
#define B_TURNOFF_1(x)   ((x) &= ((x)-1))

/* isolate right-most 1-bit in x */
#define B_ISOLATE_1(x)   ((x) &= (-(x)))

/* right-propagate right-most 1-bit in x */
#define B_PROPAGATE_1(x) ((x) |= ((x)-1))

/* isolate right-most 0-bit in x */
#define B_ISOLATE_0(x)   ((x) = ~x & ((x)+1))

/* turn on right-most 0-bit in x */
#define B_TURNON_0(x)    ((x) |= ((x)+1))

/*
** more bit hacks coming as soon as I post an article on advanced bit hacks
*/

#endif