package foo

import (
    "hash"
    "hash/fnv"
)

func harsh(fieldVals []interface{}) uint64 {
    if len(fieldVals) == 0 {
        // Avoid allocating the hasher if there are no fieldVals
        return 0
    }

    h := fnv.New64a() // .(*fnv.Sum64a)

    for _, v := range fieldVals {
        switch v := v.(type) {
        case string:
            h.Write([]byte(v))
        case int, int32:
            vi, ok := v.(int32)
            if !ok {
                vi = int32(v.(int))
            }
            b := [4]byte{}
            for i := 0; i < 4; i++ {
                b[i] = byte(vi & 0xFF)
                vi >>= 8
            }
            h.Write(b[:])
        case bool:
            if v {
                h.Write([]byte{1})
            } else {
                h.Write([]byte{0})
            }
        }
    }
    return h.Sum64()
}