github.com/gitbookio/syncgroup@v0.0.0-20181003125046-3e73b2e6a972/quickhash/fnva.go (about)

     1  package quickhash
     2  
     3  const (
     4  	offset64 uint64 = 14695981039346656037
     5  	prime64  uint64 = 1099511628211
     6  )
     7  
     8  // sum64 is an in-lined version of Go's built-in fnv 64a hash.
     9  // https://golang.org/pkg/hash/fnv/
    10  //
    11  // These lines of code are equivalent:
    12  //
    13  // hash := sum64(data)
    14  //
    15  // h := fnv.New64a()
    16  // h.Write(data)
    17  // hash := h.Sum64()
    18  //
    19  // but the former creates no allocations.
    20  func Fnv64a(data []byte) uint64 {
    21  	hash := offset64
    22  	for _, c := range data {
    23  		hash ^= uint64(c)
    24  		hash *= prime64
    25  	}
    26  	return hash
    27  }