github.com/bir3/gocompiler@v0.3.205/src/cmd/gocmd/compress/zstd/internal/xxhash/xxhash_other.go (about)

     1  //go:build (!amd64 && !arm64) || appengine || !gc || purego || noasm
     2  // +build !amd64,!arm64 appengine !gc purego noasm
     3  
     4  package xxhash
     5  
     6  // Sum64 computes the 64-bit xxHash digest of b.
     7  func Sum64(b []byte) uint64 {
     8  	// A simpler version would be
     9  	//   d := New()
    10  	//   d.Write(b)
    11  	//   return d.Sum64()
    12  	// but this is faster, particularly for small inputs.
    13  
    14  	n := len(b)
    15  	var h uint64
    16  
    17  	if n >= 32 {
    18  		v1 := primes[0] + prime2
    19  		v2 := prime2
    20  		v3 := uint64(0)
    21  		v4 := -primes[0]
    22  		for len(b) >= 32 {
    23  			v1 = round(v1, u64(b[0:8:len(b)]))
    24  			v2 = round(v2, u64(b[8:16:len(b)]))
    25  			v3 = round(v3, u64(b[16:24:len(b)]))
    26  			v4 = round(v4, u64(b[24:32:len(b)]))
    27  			b = b[32:len(b):len(b)]
    28  		}
    29  		h = rol1(v1) + rol7(v2) + rol12(v3) + rol18(v4)
    30  		h = mergeRound(h, v1)
    31  		h = mergeRound(h, v2)
    32  		h = mergeRound(h, v3)
    33  		h = mergeRound(h, v4)
    34  	} else {
    35  		h = prime5
    36  	}
    37  
    38  	h += uint64(n)
    39  
    40  	for ; len(b) >= 8; b = b[8:] {
    41  		k1 := round(0, u64(b[:8]))
    42  		h ^= k1
    43  		h = rol27(h)*prime1 + prime4
    44  	}
    45  	if len(b) >= 4 {
    46  		h ^= uint64(u32(b[:4])) * prime1
    47  		h = rol23(h)*prime2 + prime3
    48  		b = b[4:]
    49  	}
    50  	for ; len(b) > 0; b = b[1:] {
    51  		h ^= uint64(b[0]) * 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(d *Digest, b []byte) int {
    65  	v1, v2, v3, v4 := d.v1, d.v2, d.v3, d.v4
    66  	n := len(b)
    67  	for len(b) >= 32 {
    68  		v1 = round(v1, u64(b[0:8:len(b)]))
    69  		v2 = round(v2, u64(b[8:16:len(b)]))
    70  		v3 = round(v3, u64(b[16:24:len(b)]))
    71  		v4 = round(v4, u64(b[24:32:len(b)]))
    72  		b = b[32:len(b):len(b)]
    73  	}
    74  	d.v1, d.v2, d.v3, d.v4 = v1, v2, v3, v4
    75  	return n - len(b)
    76  }