cubefs

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// +build !amd64 appengine !gc purego
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package xxhash
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// Sum64 computes the 64-bit xxHash digest of b.
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func Sum64(b []byte) uint64 {
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	// A simpler version would be
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	//   d := New()
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	//   d.Write(b)
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	//   return d.Sum64()
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	// but this is faster, particularly for small inputs.
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	n := len(b)
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	var h uint64
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	if n >= 32 {
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		v1 := prime1v + prime2
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		v2 := prime2
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		v3 := uint64(0)
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		v4 := -prime1v
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		for len(b) >= 32 {
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			v1 = round(v1, u64(b[0:8:len(b)]))
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			v2 = round(v2, u64(b[8:16:len(b)]))
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			v3 = round(v3, u64(b[16:24:len(b)]))
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			v4 = round(v4, u64(b[24:32:len(b)]))
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			b = b[32:len(b):len(b)]
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		}
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		h = rol1(v1) + rol7(v2) + rol12(v3) + rol18(v4)
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		h = mergeRound(h, v1)
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		h = mergeRound(h, v2)
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		h = mergeRound(h, v3)
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		h = mergeRound(h, v4)
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	} else {
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		h = prime5
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	}
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	h += uint64(n)
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	i, end := 0, len(b)
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	for ; i+8 <= end; i += 8 {
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		k1 := round(0, u64(b[i:i+8:len(b)]))
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		h ^= k1
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		h = rol27(h)*prime1 + prime4
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	}
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	if i+4 <= end {
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		h ^= uint64(u32(b[i:i+4:len(b)])) * prime1
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		h = rol23(h)*prime2 + prime3
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		i += 4
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	}
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	for ; i < end; i++ {
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		h ^= uint64(b[i]) * prime5
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		h = rol11(h) * prime1
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	}
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	h ^= h >> 33
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	h *= prime2
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	h ^= h >> 29
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	h *= prime3
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	h ^= h >> 32
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	return h
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}
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func writeBlocks(d *Digest, b []byte) int {
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	v1, v2, v3, v4 := d.v1, d.v2, d.v3, d.v4
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	n := len(b)
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	for len(b) >= 32 {
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		v1 = round(v1, u64(b[0:8:len(b)]))
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		v2 = round(v2, u64(b[8:16:len(b)]))
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		v3 = round(v3, u64(b[16:24:len(b)]))
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		v4 = round(v4, u64(b[24:32:len(b)]))
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		b = b[32:len(b):len(b)]
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	}
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	d.v1, d.v2, d.v3, d.v4 = v1, v2, v3, v4
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	return n - len(b)
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}
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