Corentin Chary | e0e53b2 | 2011-02-04 09:06:04 +0100 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved. |
| 3 | * Written by David Howells (dhowells@redhat.com) |
| 4 | * Copyright (C) 2008 IBM Corporation |
| 5 | * Written by Rusty Russell <rusty@rustcorp.com.au> |
| 6 | * (Inspired by David Howell's find_next_bit implementation) |
| 7 | * |
| 8 | * This program is free software; you can redistribute it and/or |
| 9 | * modify it under the terms of the GNU General Public License |
| 10 | * as published by the Free Software Foundation; either version |
| 11 | * 2 of the License, or (at your option) any later version. |
| 12 | */ |
| 13 | |
Peter Maydell | aafd758 | 2016-01-29 17:49:55 +0000 | [diff] [blame] | 14 | #include "qemu/osdep.h" |
Paolo Bonzini | 1de7afc | 2012-12-17 18:20:00 +0100 | [diff] [blame] | 15 | #include "qemu/bitops.h" |
Corentin Chary | e0e53b2 | 2011-02-04 09:06:04 +0100 | [diff] [blame] | 16 | |
| 17 | #define BITOP_WORD(nr) ((nr) / BITS_PER_LONG) |
| 18 | |
| 19 | /* |
| 20 | * Find the next set bit in a memory region. |
| 21 | */ |
| 22 | unsigned long find_next_bit(const unsigned long *addr, unsigned long size, |
| 23 | unsigned long offset) |
| 24 | { |
| 25 | const unsigned long *p = addr + BITOP_WORD(offset); |
| 26 | unsigned long result = offset & ~(BITS_PER_LONG-1); |
| 27 | unsigned long tmp; |
| 28 | |
| 29 | if (offset >= size) { |
| 30 | return size; |
| 31 | } |
| 32 | size -= result; |
| 33 | offset %= BITS_PER_LONG; |
| 34 | if (offset) { |
| 35 | tmp = *(p++); |
| 36 | tmp &= (~0UL << offset); |
| 37 | if (size < BITS_PER_LONG) { |
| 38 | goto found_first; |
| 39 | } |
| 40 | if (tmp) { |
| 41 | goto found_middle; |
| 42 | } |
| 43 | size -= BITS_PER_LONG; |
| 44 | result += BITS_PER_LONG; |
| 45 | } |
Peter Lieven | 49f676a | 2013-03-26 10:58:34 +0100 | [diff] [blame] | 46 | while (size >= 4*BITS_PER_LONG) { |
| 47 | unsigned long d1, d2, d3; |
| 48 | tmp = *p; |
| 49 | d1 = *(p+1); |
| 50 | d2 = *(p+2); |
| 51 | d3 = *(p+3); |
| 52 | if (tmp) { |
| 53 | goto found_middle; |
| 54 | } |
| 55 | if (d1 | d2 | d3) { |
| 56 | break; |
| 57 | } |
| 58 | p += 4; |
| 59 | result += 4*BITS_PER_LONG; |
| 60 | size -= 4*BITS_PER_LONG; |
| 61 | } |
| 62 | while (size >= BITS_PER_LONG) { |
Corentin Chary | e0e53b2 | 2011-02-04 09:06:04 +0100 | [diff] [blame] | 63 | if ((tmp = *(p++))) { |
| 64 | goto found_middle; |
| 65 | } |
| 66 | result += BITS_PER_LONG; |
| 67 | size -= BITS_PER_LONG; |
| 68 | } |
| 69 | if (!size) { |
| 70 | return result; |
| 71 | } |
| 72 | tmp = *p; |
| 73 | |
| 74 | found_first: |
| 75 | tmp &= (~0UL >> (BITS_PER_LONG - size)); |
| 76 | if (tmp == 0UL) { /* Are any bits set? */ |
| 77 | return result + size; /* Nope. */ |
| 78 | } |
| 79 | found_middle: |
Richard Henderson | 265ce4a | 2013-02-13 17:47:37 -0800 | [diff] [blame] | 80 | return result + ctzl(tmp); |
Corentin Chary | e0e53b2 | 2011-02-04 09:06:04 +0100 | [diff] [blame] | 81 | } |
| 82 | |
| 83 | /* |
| 84 | * This implementation of find_{first,next}_zero_bit was stolen from |
| 85 | * Linus' asm-alpha/bitops.h. |
| 86 | */ |
| 87 | unsigned long find_next_zero_bit(const unsigned long *addr, unsigned long size, |
| 88 | unsigned long offset) |
| 89 | { |
| 90 | const unsigned long *p = addr + BITOP_WORD(offset); |
| 91 | unsigned long result = offset & ~(BITS_PER_LONG-1); |
| 92 | unsigned long tmp; |
| 93 | |
| 94 | if (offset >= size) { |
| 95 | return size; |
| 96 | } |
| 97 | size -= result; |
| 98 | offset %= BITS_PER_LONG; |
| 99 | if (offset) { |
| 100 | tmp = *(p++); |
| 101 | tmp |= ~0UL >> (BITS_PER_LONG - offset); |
| 102 | if (size < BITS_PER_LONG) { |
| 103 | goto found_first; |
| 104 | } |
| 105 | if (~tmp) { |
| 106 | goto found_middle; |
| 107 | } |
| 108 | size -= BITS_PER_LONG; |
| 109 | result += BITS_PER_LONG; |
| 110 | } |
| 111 | while (size & ~(BITS_PER_LONG-1)) { |
| 112 | if (~(tmp = *(p++))) { |
| 113 | goto found_middle; |
| 114 | } |
| 115 | result += BITS_PER_LONG; |
| 116 | size -= BITS_PER_LONG; |
| 117 | } |
| 118 | if (!size) { |
| 119 | return result; |
| 120 | } |
| 121 | tmp = *p; |
| 122 | |
| 123 | found_first: |
| 124 | tmp |= ~0UL << size; |
| 125 | if (tmp == ~0UL) { /* Are any bits zero? */ |
| 126 | return result + size; /* Nope. */ |
| 127 | } |
| 128 | found_middle: |
Richard Henderson | 0f9d8bd | 2013-02-13 17:47:42 -0800 | [diff] [blame] | 129 | return result + ctzl(~tmp); |
Corentin Chary | e0e53b2 | 2011-02-04 09:06:04 +0100 | [diff] [blame] | 130 | } |
| 131 | |
| 132 | unsigned long find_last_bit(const unsigned long *addr, unsigned long size) |
| 133 | { |
| 134 | unsigned long words; |
| 135 | unsigned long tmp; |
| 136 | |
| 137 | /* Start at final word. */ |
| 138 | words = size / BITS_PER_LONG; |
| 139 | |
| 140 | /* Partial final word? */ |
| 141 | if (size & (BITS_PER_LONG-1)) { |
| 142 | tmp = (addr[words] & (~0UL >> (BITS_PER_LONG |
| 143 | - (size & (BITS_PER_LONG-1))))); |
| 144 | if (tmp) { |
| 145 | goto found; |
| 146 | } |
| 147 | } |
| 148 | |
| 149 | while (words) { |
| 150 | tmp = addr[--words]; |
| 151 | if (tmp) { |
| 152 | found: |
Richard Henderson | 4932398 | 2013-02-13 17:47:41 -0800 | [diff] [blame] | 153 | return words * BITS_PER_LONG + BITS_PER_LONG - 1 - clzl(tmp); |
Corentin Chary | e0e53b2 | 2011-02-04 09:06:04 +0100 | [diff] [blame] | 154 | } |
| 155 | } |
| 156 | |
| 157 | /* Not found */ |
| 158 | return size; |
| 159 | } |