bitops.h

xen虚拟机源代码安装包

#ifndef _LINUX_BITOPS_H
#define _LINUX_BITOPS_H
#include <asm/types.h>

/*
 * ffs: find first bit set. This is defined the same way as
 * the libc and compiler builtin ffs routines, therefore
 * differs in spirit from the above ffz (man ffs).
 */

static inline int generic_ffs(int x)
{
    int r = 1;

    if (!x)
        return 0;
    if (!(x & 0xffff)) {
        x >>= 16;
        r += 16;
    }
    if (!(x & 0xff)) {
        x >>= 8;
        r += 8;
    }
    if (!(x & 0xf)) {
        x >>= 4;
        r += 4;
    }
    if (!(x & 3)) {
        x >>= 2;
        r += 2;
    }
    if (!(x & 1)) {
        x >>= 1;
        r += 1;
    }
    return r;
}

/*
 * fls: find last bit set.
 */

static __inline__ int generic_fls(int x)
{
    int r = 32;

    if (!x)
        return 0;
    if (!(x & 0xffff0000u)) {
        x <<= 16;
        r -= 16;
    }
    if (!(x & 0xff000000u)) {
        x <<= 8;
        r -= 8;
    }
    if (!(x & 0xf0000000u)) {
        x <<= 4;
        r -= 4;
    }
    if (!(x & 0xc0000000u)) {
        x <<= 2;
        r -= 2;
    }
    if (!(x & 0x80000000u)) {
        x <<= 1;
        r -= 1;
    }
    return r;
}

/*
 * Include this here because some architectures need generic_ffs/fls in
 * scope
 */
#include <asm/bitops.h>


static inline int generic_fls64(__u64 x)
{
    __u32 h = x >> 32;
    if (h)
        return fls(x) + 32;
    return fls(x);
}

static __inline__ int get_bitmask_order(unsigned int count)
{
    int order;
    
    order = fls(count);
    return order;   /* We could be slightly more clever with -1 here... */
}

static __inline__ int get_count_order(unsigned int count)
{
    int order;

    order = fls(count) - 1;
    if (count & (count - 1))
        order++;
    return order;
}

/*
 * hweightN: returns the hamming weight (i.e. the number
 * of bits set) of a N-bit word
 */

static inline unsigned int generic_hweight32(unsigned int w)
{
    unsigned int res = (w & 0x55555555) + ((w >> 1) & 0x55555555);
    res = (res & 0x33333333) + ((res >> 2) & 0x33333333);
    res = (res & 0x0F0F0F0F) + ((res >> 4) & 0x0F0F0F0F);
    res = (res & 0x00FF00FF) + ((res >> 8) & 0x00FF00FF);
    return (res & 0x0000FFFF) + ((res >> 16) & 0x0000FFFF);
}

static inline unsigned int generic_hweight16(unsigned int w)
{
    unsigned int res = (w & 0x5555) + ((w >> 1) & 0x5555);
    res = (res & 0x3333) + ((res >> 2) & 0x3333);
    res = (res & 0x0F0F) + ((res >> 4) & 0x0F0F);
    return (res & 0x00FF) + ((res >> 8) & 0x00FF);
}

static inline unsigned int generic_hweight8(unsigned int w)
{
    unsigned int res = (w & 0x55) + ((w >> 1) & 0x55);
    res = (res & 0x33) + ((res >> 2) & 0x33);
    return (res & 0x0F) + ((res >> 4) & 0x0F);
}

static inline unsigned long generic_hweight64(__u64 w)
{
#if BITS_PER_LONG < 64
    return generic_hweight32((unsigned int)(w >> 32)) +
        generic_hweight32((unsigned int)w);
#else
    u64 res;
    res = (w & 0x5555555555555555ul) + ((w >> 1) & 0x5555555555555555ul);
    res = (res & 0x3333333333333333ul) + ((res >> 2) & 0x3333333333333333ul);
    res = (res & 0x0F0F0F0F0F0F0F0Ful) + ((res >> 4) & 0x0F0F0F0F0F0F0F0Ful);
    res = (res & 0x00FF00FF00FF00FFul) + ((res >> 8) & 0x00FF00FF00FF00FFul);
    res = (res & 0x0000FFFF0000FFFFul) + ((res >> 16) & 0x0000FFFF0000FFFFul);
    return (res & 0x00000000FFFFFFFFul) + ((res >> 32) & 0x00000000FFFFFFFFul);
#endif
}

static inline unsigned long hweight_long(unsigned long w)
{
    return sizeof(w) == 4 ? generic_hweight32(w) : generic_hweight64(w);
}

/*
 * rol32 - rotate a 32-bit value left
 *
 * @word: value to rotate
 * @shift: bits to roll
 */
static inline __u32 rol32(__u32 word, unsigned int shift)
{
    return (word << shift) | (word >> (32 - shift));
}

/*
 * ror32 - rotate a 32-bit value right
 *
 * @word: value to rotate
 * @shift: bits to roll
 */
static inline __u32 ror32(__u32 word, unsigned int shift)
{
    return (word >> shift) | (word << (32 - shift));
}

#endif