include/linux/bitops.h

   1 #ifndef _LINUX_BITOPS_H
   2 #define _LINUX_BITOPS_H
   3
   4 #include <asm/types.h>
   5
   6 /*
   7  * ffs: find first bit set. This is defined the same way as
   8  * the libc and compiler builtin ffs routines, therefore
   9  * differs in spirit from the above ffz (man ffs).
  10  */
  11
  12 static inline int generic_ffs(int x)
  13 {
  14         int r = 1;
  15
  16         if (!x)
  17                 return 0;
  18         if (!(x & 0xffff)) {
  19                 x >>= 16;
  20                 r += 16;
  21         }
  22         if (!(x & 0xff)) {
  23                 x >>= 8;
  24                 r += 8;
  25         }
  26         if (!(x & 0xf)) {
  27                 x >>= 4;
  28                 r += 4;
  29         }
  30         if (!(x & 3)) {
  31                 x >>= 2;
  32                 r += 2;
  33         }
  34         if (!(x & 1)) {
  35                 x >>= 1;
  36                 r += 1;
  37         }
  38         return r;
  39 }
  40
  41 /**
  42  * fls - find last (most-significant) bit set
  43  * @x: the word to search
  44  *
  45  * This is defined the same way as ffs.
  46  * Note fls(0) = 0, fls(1) = 1, fls(0x80000000) = 32.
  47  */
  48 static inline int generic_fls(int x)
  49 {
  50         int r = 32;
  51
  52         if (!x)
  53                 return 0;
  54         if (!(x & 0xffff0000u)) {
  55                 x <<= 16;
  56                 r -= 16;
  57         }
  58         if (!(x & 0xff000000u)) {
  59                 x <<= 8;
  60                 r -= 8;
  61         }
  62         if (!(x & 0xf0000000u)) {
  63                 x <<= 4;
  64                 r -= 4;
  65         }
  66         if (!(x & 0xc0000000u)) {
  67                 x <<= 2;
  68                 r -= 2;
  69         }
  70         if (!(x & 0x80000000u)) {
  71                 x <<= 1;
  72                 r -= 1;
  73         }
  74         return r;
  75 }
  76
  77
  78 /*
  79  * hweightN: returns the hamming weight (i.e. the number
  80  * of bits set) of a N-bit word
  81  */
  82
  83 static inline unsigned int generic_hweight32(unsigned int w)
  84 {
  85         unsigned int res = (w & 0x55555555) + ((w >> 1) & 0x55555555);
  86         res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
  87         res = (res & 0x0F0F0F0F) + ((res >> 4) & 0x0F0F0F0F);
  88         res = (res & 0x00FF00FF) + ((res >> 8) & 0x00FF00FF);
  89         return (res & 0x0000FFFF) + ((res >> 16) & 0x0000FFFF);
  90 }
  91
  92 static inline unsigned int generic_hweight16(unsigned int w)
  93 {
  94         unsigned int res = (w & 0x5555) + ((w >> 1) & 0x5555);
  95         res = (res & 0x3333) + ((res >> 2) & 0x3333);
  96         res = (res & 0x0F0F) + ((res >> 4) & 0x0F0F);
  97         return (res & 0x00FF) + ((res >> 8) & 0x00FF);
  98 }
  99
 100 static inline unsigned int generic_hweight8(unsigned int w)
 101 {
 102         unsigned int res = (w & 0x55) + ((w >> 1) & 0x55);
 103         res = (res & 0x33) + ((res >> 2) & 0x33);
 104         return (res & 0x0F) + ((res >> 4) & 0x0F);
 105 }
 106
 107 #define BIT_MASK(nr)            (1UL << ((nr) % BITS_PER_LONG))
 108 #define BIT_WORD(nr)            ((nr) / BITS_PER_LONG)
 109
 110 #include <asm/bitops.h>
 111
 112 /* linux/include/asm-generic/bitops/non-atomic.h */
 113
 114 #ifndef PLATFORM__SET_BIT
 115 # define __set_bit generic_set_bit
 116 #endif
 117
 118 #ifndef PLATFORM__CLEAR_BIT
 119 # define __clear_bit generic_clear_bit
 120 #endif
 121
 122 #ifndef PLATFORM_FFS
 123 # define ffs generic_ffs
 124 #endif
 125
 126 #ifndef PLATFORM_FLS
 127 # define fls generic_fls
 128 #endif
 129
 130 /**
 131  * __set_bit - Set a bit in memory
 132  * @nr: the bit to set
 133  * @addr: the address to start counting from
 134  *
 135  * Unlike set_bit(), this function is non-atomic and may be reordered.
 136  * If it's called on the same region of memory simultaneously, the effect
 137  * may be that only one operation succeeds.
 138  */
 139 static inline void generic_set_bit(int nr, volatile unsigned long *addr)
 140 {
 141         unsigned long mask = BIT_MASK(nr);
 142         unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
 143
 144         *p  |= mask;
 145 }
 146
 147 static inline void generic_clear_bit(int nr, volatile unsigned long *addr)
 148 {
 149         unsigned long mask = BIT_MASK(nr);
 150         unsigned long *p = ((unsigned long *)addr) + BIT_WORD(nr);
 151
 152         *p &= ~mask;
 153 }
 154
 155 #endif