bitmap(1)
bitmaps利用一个或多个ulong类型来提供位数组，在一个给定位图中的有效位数不需要是确定的BITS_PER_LONG的倍数，位图接口和可用运算列在bitmap.h中。lib/bitmap.c中的函数实现适用于所有结构，特定于不同结构的函数实现位于include/asm-<arch>/bitop.h头文件以及arch/<arch>相关文件中。
bitmap_zero(dst, nbits) *dst = 0UL
bitmap_fill(dst, nbits) *dst = ~0UL
bitmap_copy(dst, src, nbits) *dst = *src
bitmap_and(dst, src1, src2, nbits) *dst = *src1 & *src2
bitmap_or(dst, src1, src2, nbits) *dst = *src1 | *src2
bitmap_xor(dst, src1, src2, nbits) *dst = *src1 ^ *src2
bitmap_andnot(dst, src1, src2, nbits) *dst = *src1 & ~(*src2)
bitmap_complement(dst, src, nbits) *dst = ~(*src)
bitmap_equal(src1, src2, nbits) Are *src1 and *src2 equal?
bitmap_intersects(src1, src2, nbits) Do *src1 and *src2 overlap?
bitmap_subset(src1, src2, nbits) Is *src1 a subset of *src2?
bitmap_empty(src, nbits) Are all bits zero in *src?
bitmap_full(src, nbits) Are all bits set in *src?
bitmap_weight(src, nbits) Hamming Weight: number set bits
bitmap_set(dst, pos, nbits) Set specified bit area
bitmap_clear(dst, pos, nbits) Clear specified bit area
bitmap_find_next_zero_area(buf, len, pos, n, mask) Find bit free area
bitmap_shift_right(dst, src, n, nbits) *dst = *src >> n
bitmap_shift_left(dst, src, n, nbits) *dst = *src << n
bitmap_remap(dst, src, old, new, nbits) *dst = map(old, new)(src)
bitmap_bitremap(oldbit, old, new, nbits) newbit = map(old, new)(oldbit)
bitmap_onto(dst, orig, relmap, nbits) *dst = orig relative to relmap
bitmap_fold(dst, orig, sz, nbits) dst bits = orig bits mod sz
bitmap_scnprintf(buf, len, src, nbits) Print bitmap src to buf
bitmap_parse(buf, buflen, dst, nbits) Parse bitmap dst from kernel buf
bitmap_parse_user(ubuf, ulen, dst, nbits) Parse bitmap dst from user buf
bitmap_scnlistprintf(buf, len, src, nbits) Print bitmap src as list to buf
bitmap_parselist(buf, dst, nbits) Parse bitmap dst from kernel buf
bitmap_parselist_user(buf, dst, nbits) Parse bitmap dst from user buf
bitmap_find_free_region(bitmap, bits, order) Find and allocate bit region
bitmap_release_region(bitmap, pos, order) Free specified bit region
bitmap_allocate_region(bitmap, pos, order) Allocate specified bit region
asm/bitops.h中的下列操作也适用于位图
set_bit(bit, addr) *addr |= bit
clear_bit(bit, addr) *addr &= ~bit
change_bit(bit, addr) *addr ^= bit
test_bit(bit, addr) Is bit set in *addr?
test_and_set_bit(bit, addr) Set bit and return old value
test_and_clear_bit(bit, addr) Clear bit and return old value
test_and_change_bit(bit, addr) Change bit and return old value
find_first_zero_bit(addr, nbits) Position first zero bit in *addr
find_first_bit(addr, nbits) Position first set bit in *addr
find_next_zero_bit(addr, nbits, bit) Position next zero bit in *addr >= bit
find_next_bit(addr, nbits, bit) Position next set bit in *addr >= bit
static inline void set_bit(int nr, unsigned long *addr)
{ addr[nr / BITS_PER_LONG] |= 1UL << (nr % BITS_PER_LONG);} // 除法应尽量改为移位操作
static inline void clear_bit(int nr, unsigned long *addr)
{ addr[nr / BITS_PER_LONG] &= ~(1UL << (nr % BITS_PER_LONG)); }
static __always_inline int test_bit(unsigned int nr, const unsigned long *addr)
{ return ((1UL << (nr % BITS_PER_LONG)) & (((unsigned long *)addr)[nr / BITS_PER_LONG])) != 0; }
#define DIV_ROUND_UP(n,d) (((n) + (d) - 1) / (d))
#define BITS_TO_LONGS(nr) DIV_ROUND_UP(nr, BITS_PER_BYTE * sizeof(long))
#define DECLARE_BITMAP(name,bits) unsigned long name[BITS_TO_LONGS(bits)]
typedef struct cpumask { DECLARE_BITMAP(bits, NR_CPUS); } cpumask_t;