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 129