xxhash_other.go

Documentation: github.com/cespare/xxhash

     1  // +build !amd64 appengine !gc purego
     2  
     3  package xxhash
     4  
     5  // Sum64 computes the 64-bit xxHash digest of b.
     6  func Sum64(b []byte) uint64 {
     7  	// A simpler version would be
     8  	//   x := New()
     9  	//   x.Write(b)
    10  	//   return x.Sum64()
    11  	// but this is faster, particularly for small inputs.
    12  
    13  	n := len(b)
    14  	var h uint64
    15  
    16  	if n >= 32 {
    17  		v1 := prime1v + prime2
    18  		v2 := prime2
    19  		v3 := uint64(0)
    20  		v4 := -prime1v
    21  		for len(b) >= 32 {
    22  			v1 = round(v1, u64(b[0:8:len(b)]))
    23  			v2 = round(v2, u64(b[8:16:len(b)]))
    24  			v3 = round(v3, u64(b[16:24:len(b)]))
    25  			v4 = round(v4, u64(b[24:32:len(b)]))
    26  			b = b[32:len(b):len(b)]
    27  		}
    28  		h = rol1(v1) + rol7(v2) + rol12(v3) + rol18(v4)
    29  		h = mergeRound(h, v1)
    30  		h = mergeRound(h, v2)
    31  		h = mergeRound(h, v3)
    32  		h = mergeRound(h, v4)
    33  	} else {
    34  		h = prime5
    35  	}
    36  
    37  	h += uint64(n)
    38  
    39  	i, end := 0, len(b)
    40  	for ; i+8 <= end; i += 8 {
    41  		k1 := round(0, u64(b[i:i+8:len(b)]))
    42  		h ^= k1
    43  		h = rol27(h)*prime1 + prime4
    44  	}
    45  	if i+4 <= end {
    46  		h ^= uint64(u32(b[i:i+4:len(b)])) * prime1
    47  		h = rol23(h)*prime2 + prime3
    48  		i += 4
    49  	}
    50  	for ; i < end; i++ {
    51  		h ^= uint64(b[i]) * prime5
    52  		h = rol11(h) * prime1
    53  	}
    54  
    55  	h ^= h >> 33
    56  	h *= prime2
    57  	h ^= h >> 29
    58  	h *= prime3
    59  	h ^= h >> 32
    60  
    61  	return h
    62  }
    63  
    64  func writeBlocks(x *xxh, b []byte) []byte {
    65  	v1, v2, v3, v4 := x.v1, x.v2, x.v3, x.v4
    66  	for len(b) >= 32 {
    67  		v1 = round(v1, u64(b[0:8:len(b)]))
    68  		v2 = round(v2, u64(b[8:16:len(b)]))
    69  		v3 = round(v3, u64(b[16:24:len(b)]))
    70  		v4 = round(v4, u64(b[24:32:len(b)]))
    71  		b = b[32:len(b):len(b)]
    72  	}
    73  	x.v1, x.v2, x.v3, x.v4 = v1, v2, v3, v4
    74  	return b
    75  }
    76
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