38 lines
466 B
Go
38 lines
466 B
Go
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// +build !amd64 appengine
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package bits
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// Clz counts leading zeroes
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func Clz(x uint64) uint64 {
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var n uint64
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n = 1
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if (x >> 32) == 0 {
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n = n + 32
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x = x << 32
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}
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if (x >> (32 + 16)) == 0 {
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n = n + 16
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x = x << 16
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}
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if (x >> (32 + 16 + 8)) == 0 {
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n = n + 8
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x = x << 8
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}
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if (x >> (32 + 16 + 8 + 4)) == 0 {
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n = n + 4
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x = x << 4
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}
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if (x >> (32 + 16 + 8 + 4 + 2)) == 0 {
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n = n + 2
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x = x << 2
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}
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n = n - (x >> 63)
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return uint64(n)
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}
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