find_next_bit.c

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/* find_next_bit.c: fallback find next bit implementation
 *
 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
 * Written by David Howells ([email protected])
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; either version
 * 2 of the License, or (at your option) any later version.
 */

#include <linux/bitops.h>
#include <linux/export.h>
#include <asm/types.h>
#include <asm/byteorder.h>

#define BITOP_WORD(nr)      ((nr) / BITS_PER_LONG)

#ifndef find_next_bit
/*
 * Find the next set bit in a memory region.
 */
unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
                unsigned long offset)
{
    const unsigned long *p = addr + BITOP_WORD(offset);
    unsigned long result = offset & ~(BITS_PER_LONG-1);
    unsigned long tmp;

    if (offset >= size)
        return size;
    size -= result;
    offset %= BITS_PER_LONG;
    if (offset) {
        tmp = *(p++);
        tmp &= (~0UL << offset);
        if (size < BITS_PER_LONG)
            goto found_first;
        if (tmp)
            goto found_middle;
        size -= BITS_PER_LONG;
        result += BITS_PER_LONG;
    }
    while (size & ~(BITS_PER_LONG-1)) {
        if ((tmp = *(p++)))
            goto found_middle;
        result += BITS_PER_LONG;
        size -= BITS_PER_LONG;
    }
    if (!size)
        return result;
    tmp = *p;

found_first:
    tmp &= (~0UL >> (BITS_PER_LONG - size));
    if (tmp == 0UL)     /* Are any bits set? */
        return result + size;   /* Nope. */
found_middle:
    return result + __ffs(tmp);
}
EXPORT_SYMBOL(find_next_bit);
#endif

#ifndef find_next_zero_bit
/*
 * This implementation of find_{first,next}_zero_bit was stolen from
 * Linus' asm-alpha/bitops.h.
 */
unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
                 unsigned long offset)
{
    const unsigned long *p = addr + BITOP_WORD(offset);
    unsigned long result = offset & ~(BITS_PER_LONG-1);
    unsigned long tmp;

    if (offset >= size)
        return size;
    size -= result;
    offset %= BITS_PER_LONG;
    if (offset) {
        tmp = *(p++);
        tmp |= ~0UL >> (BITS_PER_LONG - offset);
        if (size < BITS_PER_LONG)
            goto found_first;
        if (~tmp)
            goto found_middle;
        size -= BITS_PER_LONG;
        result += BITS_PER_LONG;
    }
    while (size & ~(BITS_PER_LONG-1)) {
        if (~(tmp = *(p++)))
            goto found_middle;
        result += BITS_PER_LONG;
        size -= BITS_PER_LONG;
    }
    if (!size)
        return result;
    tmp = *p;

found_first:
    tmp |= ~0UL << size;
    if (tmp == ~0UL)    /* Are any bits zero? */
        return result + size;   /* Nope. */
found_middle:
    return result + ffz(tmp);
}
EXPORT_SYMBOL(find_next_zero_bit);
#endif

#ifndef find_first_bit
/*
 * Find the first set bit in a memory region.
 */
unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
{
    const unsigned long *p = addr;
    unsigned long result = 0;
    unsigned long tmp;

    while (size & ~(BITS_PER_LONG-1)) {
        if ((tmp = *(p++)))
            goto found;
        result += BITS_PER_LONG;
        size -= BITS_PER_LONG;
    }
    if (!size)
        return result;

    tmp = (*p) & (~0UL >> (BITS_PER_LONG - size));
    if (tmp == 0UL)     /* Are any bits set? */
        return result + size;   /* Nope. */
found:
    return result + __ffs(tmp);
}
EXPORT_SYMBOL(find_first_bit);
#endif

#ifndef find_first_zero_bit
/*
 * Find the first cleared bit in a memory region.
 */
unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)
{
    const unsigned long *p = addr;
    unsigned long result = 0;
    unsigned long tmp;

    while (size & ~(BITS_PER_LONG-1)) {
        if (~(tmp = *(p++)))
            goto found;
        result += BITS_PER_LONG;
        size -= BITS_PER_LONG;
    }
    if (!size)
        return result;

    tmp = (*p) | (~0UL << size);
    if (tmp == ~0UL)    /* Are any bits zero? */
        return result + size;   /* Nope. */
found:
    return result + ffz(tmp);
}
EXPORT_SYMBOL(find_first_zero_bit);
#endif

#ifdef __BIG_ENDIAN

/* include/linux/byteorder does not support "unsigned long" type */
static inline unsigned long ext2_swabp(const unsigned long * x)
{
#if BITS_PER_LONG == 64
    return (unsigned long) __swab64p((u64 *) x);
#elif BITS_PER_LONG == 32
    return (unsigned long) __swab32p((u32 *) x);
#else
#error BITS_PER_LONG not defined
#endif
}

/* include/linux/byteorder doesn't support "unsigned long" type */
static inline unsigned long ext2_swab(const unsigned long y)
{
#if BITS_PER_LONG == 64
    return (unsigned long) __swab64((u64) y);
#elif BITS_PER_LONG == 32
    return (unsigned long) __swab32((u32) y);
#else
#error BITS_PER_LONG not defined
#endif
}

#ifndef find_next_zero_bit_le
unsigned long find_next_zero_bit_le(const void *addr, unsigned
        long size, unsigned long offset)
{
    const unsigned long *p = addr;
    unsigned long result = offset & ~(BITS_PER_LONG - 1);
    unsigned long tmp;

    if (offset >= size)
        return size;
    p += BITOP_WORD(offset);
    size -= result;
    offset &= (BITS_PER_LONG - 1UL);
    if (offset) {
        tmp = ext2_swabp(p++);
        tmp |= (~0UL >> (BITS_PER_LONG - offset));
        if (size < BITS_PER_LONG)
            goto found_first;
        if (~tmp)
            goto found_middle;
        size -= BITS_PER_LONG;
        result += BITS_PER_LONG;
    }

    while (size & ~(BITS_PER_LONG - 1)) {
        if (~(tmp = *(p++)))
            goto found_middle_swap;
        result += BITS_PER_LONG;
        size -= BITS_PER_LONG;
    }
    if (!size)
        return result;
    tmp = ext2_swabp(p);
found_first:
    tmp |= ~0UL << size;
    if (tmp == ~0UL)    /* Are any bits zero? */
        return result + size; /* Nope. Skip ffz */
found_middle:
    return result + ffz(tmp);

found_middle_swap:
    return result + ffz(ext2_swab(tmp));
}
EXPORT_SYMBOL(find_next_zero_bit_le);
#endif

#ifndef find_next_bit_le
unsigned long find_next_bit_le(const void *addr, unsigned
        long size, unsigned long offset)
{
    const unsigned long *p = addr;
    unsigned long result = offset & ~(BITS_PER_LONG - 1);
    unsigned long tmp;

    if (offset >= size)
        return size;
    p += BITOP_WORD(offset);
    size -= result;
    offset &= (BITS_PER_LONG - 1UL);
    if (offset) {
        tmp = ext2_swabp(p++);
        tmp &= (~0UL << offset);
        if (size < BITS_PER_LONG)
            goto found_first;
        if (tmp)
            goto found_middle;
        size -= BITS_PER_LONG;
        result += BITS_PER_LONG;
    }

    while (size & ~(BITS_PER_LONG - 1)) {
        tmp = *(p++);
        if (tmp)
            goto found_middle_swap;
        result += BITS_PER_LONG;
        size -= BITS_PER_LONG;
    }
    if (!size)
        return result;
    tmp = ext2_swabp(p);
found_first:
    tmp &= (~0UL >> (BITS_PER_LONG - size));
    if (tmp == 0UL)     /* Are any bits set? */
        return result + size; /* Nope. */
found_middle:
    return result + __ffs(tmp);

found_middle_swap:
    return result + __ffs(ext2_swab(tmp));
}
EXPORT_SYMBOL(find_next_bit_le);
#endif

#endif /* __BIG_ENDIAN */