LXR linux/tools/lib/find

   1/* bit search implementation
   2 *
   3 * Copied from lib/find_bit.c to tools/lib/find_bit.c
   4 *
   5 * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
   6 * Written by David Howells (dhowells@redhat.com)
   7 *
   8 * Copyright (C) 2008 IBM Corporation
   9 * 'find_last_bit' is written by Rusty Russell <rusty@rustcorp.com.au>
  10 * (Inspired by David Howell's find_next_bit implementation)
  11 *
  12 * Rewritten by Yury Norov <yury.norov@gmail.com> to decrease
  13 * size and improve performance, 2015.
  14 *
  15 * This program is free software; you can redistribute it and/or
  16 * modify it under the terms of the GNU General Public License
  17 * as published by the Free Software Foundation; either version
  18 * 2 of the License, or (at your option) any later version.
  19 */
  20
  21#include <linux/bitops.h>
  22#include <linux/bitmap.h>
  23#include <linux/kernel.h>
  24
  25#if !defined(find_next_bit) || !defined(find_next_zero_bit) || \
  26                !defined(find_next_and_bit)
  27
  28/*
  29 * This is a common helper function for find_next_bit, find_next_zero_bit, and
  30 * find_next_and_bit. The differences are:
  31 *  - The "invert" argument, which is XORed with each fetched word before
  32 *    searching it for one bits.
  33 *  - The optional "addr2", which is anded with "addr1" if present.
  34 */
  35static inline unsigned long _find_next_bit(const unsigned long *addr1,
  36                const unsigned long *addr2, unsigned long nbits,
  37                unsigned long start, unsigned long invert)
  38{
  39        unsigned long tmp;
  40
  41        if (unlikely(start >= nbits))
  42                return nbits;
  43
  44        tmp = addr1[start / BITS_PER_LONG];
  45        if (addr2)
  46                tmp &= addr2[start / BITS_PER_LONG];
  47        tmp ^= invert;
  48
  49        /* Handle 1st word. */
  50        tmp &= BITMAP_FIRST_WORD_MASK(start);
  51        start = round_down(start, BITS_PER_LONG);
  52
  53        while (!tmp) {
  54                start += BITS_PER_LONG;
  55                if (start >= nbits)
  56                        return nbits;
  57
  58                tmp = addr1[start / BITS_PER_LONG];
  59                if (addr2)
  60                        tmp &= addr2[start / BITS_PER_LONG];
  61                tmp ^= invert;
  62        }
  63
  64        return min(start + __ffs(tmp), nbits);
  65}
  66#endif
  67
  68#ifndef find_next_bit
  69/*
  70 * Find the next set bit in a memory region.
  71 */
  72unsigned long find_next_bit(const unsigned long *addr, unsigned long size,
  73                            unsigned long offset)
  74{
  75        return _find_next_bit(addr, NULL, size, offset, 0UL);
  76}
  77#endif
  78
  79#ifndef find_first_bit
  80/*
  81 * Find the first set bit in a memory region.
  82 */
  83unsigned long find_first_bit(const unsigned long *addr, unsigned long size)
  84{
  85        unsigned long idx;
  86
  87        for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
  88                if (addr[idx])
  89                        return min(idx * BITS_PER_LONG + __ffs(addr[idx]), size);
  90        }
  91
  92        return size;
  93}
  94#endif
  95
  96#ifndef find_first_zero_bit
  97/*
  98 * Find the first cleared bit in a memory region.
  99 */
 100unsigned long find_first_zero_bit(const unsigned long *addr, unsigned long size)
 101{
 102        unsigned long idx;
 103
 104        for (idx = 0; idx * BITS_PER_LONG < size; idx++) {
 105                if (addr[idx] != ~0UL)
 106                        return min(idx * BITS_PER_LONG + ffz(addr[idx]), size);
 107        }
 108
 109        return size;
 110}
 111#endif
 112
 113#ifndef find_next_zero_bit
 114unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size,
 115                                 unsigned long offset)
 116{
 117        return _find_next_bit(addr, NULL, size, offset, ~0UL);
 118}
 119#endif
 120
 121#ifndef find_next_and_bit
 122unsigned long find_next_and_bit(const unsigned long *addr1,
 123                const unsigned long *addr2, unsigned long size,
 124                unsigned long offset)
 125{
 126        return _find_next_bit(addr1, addr2, size, offset, 0UL);
 127}
 128#endif
 129