Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
kernel
os
linux
bitmap: add bitmap_weight_from()
The function calculates a Hamming weight of a bitmap starting from an
arbitrary bit.
Signed-off-by: Yury Norov <ynorov@nvidia.com>
+59
+33
include/linux/bitmap.h
+33
include/linux/bitmap.h
···
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* bitmap_weight(src, nbits) Hamming Weight: number set bits
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* bitmap_weight_and(src1, src2, nbits) Hamming Weight of and'ed bitmap
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* bitmap_weight_andnot(src1, src2, nbits) Hamming Weight of andnot'ed bitmap
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* bitmap_weight_from(src, start, end) Hamming Weight starting from @start
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* bitmap_set(dst, pos, nbits) Set specified bit area
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* bitmap_clear(dst, pos, nbits) Clear specified bit area
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* bitmap_find_next_zero_area(buf, len, pos, n, mask) Find bit free area
···
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if (small_const_nbits(nbits))
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return hweight_long(*src1 & ~(*src2) & BITMAP_LAST_WORD_MASK(nbits));
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return __bitmap_weight_andnot(src1, src2, nbits);
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+
}
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/**
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* bitmap_weight_from - Hamming weight for a memory region
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* @bitmap: The base address
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* @start: The bitnumber to starts weighting
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* @end: the bitmap size in bits
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*
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* Returns the number of set bits in the region. If @start >= @end,
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* return >= end.
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*/
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static __always_inline
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unsigned long bitmap_weight_from(const unsigned long *bitmap,
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unsigned int start, unsigned int end)
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{
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unsigned long w;
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+
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if (unlikely(start >= end))
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return end;
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+
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if (small_const_nbits(end))
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return hweight_long(*bitmap & GENMASK(end - 1, start));
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bitmap += start / BITS_PER_LONG;
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/* Opencode round_down() to not include math.h */
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end -= start & ~(BITS_PER_LONG - 1);
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start %= BITS_PER_LONG;
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w = bitmap_weight(bitmap, end);
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if (start)
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w -= hweight_long(*bitmap & BITMAP_LAST_WORD_MASK(start));
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return w;
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}
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static __always_inline
+26
lib/test_bitmap.c
+26
lib/test_bitmap.c
···
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}
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}
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static void __init test_bitmap_weight(void)
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{
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unsigned int bit, w1, w2, w;
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DECLARE_BITMAP(b, 30);
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bitmap_parselist("all:1/2", b, 30);
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/* Test inline implementation */
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w = bitmap_weight(b, 30);
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w1 = bitmap_weight(b, 15);
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w2 = bitmap_weight_from(b, 15, 30);
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expect_eq_uint(15, w);
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expect_eq_uint(8, w1);
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expect_eq_uint(7, w2);
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+
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/* Test outline implementation */
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w = bitmap_weight(exp1, EXP1_IN_BITS);
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for (bit = 0; bit < EXP1_IN_BITS; bit++) {
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w1 = bitmap_weight(exp1, bit);
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w2 = bitmap_weight_from(exp1, bit, EXP1_IN_BITS);
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expect_eq_uint(w1 + w2, w);
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}
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}
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static void __init test_for_each_clear_bit(void)
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{
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DECLARE_BITMAP(orig, 500);
···
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test_bitmap_const_eval();
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test_bitmap_read_write();
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test_bitmap_read_perf();
1447
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test_bitmap_weight();
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test_bitmap_write_perf();
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test_find_nth_bit();