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77 lines
1.5 KiB
Go
77 lines
1.5 KiB
Go
// +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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