tools/lib/find_bit.c

   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  */
  35 static 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  */
  72 unsigned 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  */
  83 unsigned 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  */
 100 unsigned 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
 114 unsigned 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
 122 unsigned 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