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37 lines
461 B
37 lines
461 B
5 years ago
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// +build !go1.9
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package roaring
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// LeadingZeroBits returns the number of consecutive most significant zero
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// bits of x.
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func countLeadingZeros(i uint64) int {
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if i == 0 {
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return 64
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}
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n := 1
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x := uint32(i >> 32)
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if x == 0 {
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n += 32
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x = uint32(i)
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}
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if (x >> 16) == 0 {
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n += 16
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x <<= 16
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}
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if (x >> 24) == 0 {
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n += 8
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x <<= 8
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}
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if x>>28 == 0 {
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n += 4
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x <<= 4
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}
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if x>>30 == 0 {
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n += 2
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x <<= 2
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}
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n -= int(x >> 31)
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return n
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}
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