vendor/github.com/allegro/bigcache/fnv.go


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package bigcache

// newDefaultHasher returns a new 64-bit FNV-1a Hasher which makes no memory allocations.
// Its Sum64 method will lay the value out in big-endian byte order.
// See https://en.wikipedia.org/wiki/Fowler–Noll–Vo_hash_function
func newDefaultHasher() Hasher {
    return fnv64a{}
}

type fnv64a struct{}

const (
    // offset64 FNVa offset basis. See https://en.wikipedia.org/wiki/Fowler–Noll–Vo_hash_function#FNV-1a_hash
    offset64 = 14695981039346656037
    // prime64 FNVa prime value. See https://en.wikipedia.org/wiki/Fowler–Noll–Vo_hash_function#FNV-1a_hash
    prime64 = 1099511628211
)

// Sum64 gets the string and returns its uint64 hash value.
func (f fnv64a) Sum64(key string) uint64 {
    var hash uint64 = offset64
    for i := 0; i < len(key); i++ {
        hash ^= uint64(key[i])
        hash *= prime64
    }

    return hash
}