64 lines
1.2 KiB
Go
64 lines
1.2 KiB
Go
package hasher
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import (
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"hash/maphash"
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"strconv"
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"github.com/navidrome/navidrome/utils/random"
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)
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var instance = NewHasher()
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func Reseed(id string) {
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instance.Reseed(id)
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}
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func SetSeed(id string, seed string) {
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instance.SetSeed(id, seed)
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}
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func HashFunc() func(id, str string) uint64 {
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return instance.HashFunc()
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}
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type Hasher struct {
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seeds map[string]string
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hashSeed maphash.Seed
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}
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func NewHasher() *Hasher {
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h := new(Hasher)
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h.seeds = make(map[string]string)
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h.hashSeed = maphash.MakeSeed()
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return h
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}
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// SetSeed sets a seed for the given id
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func (h *Hasher) SetSeed(id string, seed string) {
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h.seeds[id] = seed
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}
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// Reseed generates a new random seed for the given id
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func (h *Hasher) Reseed(id string) {
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_ = h.reseed(id)
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}
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func (h *Hasher) reseed(id string) string {
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seed := strconv.FormatUint(random.Uint64(), 36)
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h.seeds[id] = seed
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return seed
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}
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// HashFunc returns a function that hashes a string using the seed for the given id
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func (h *Hasher) HashFunc() func(id, str string) uint64 {
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return func(id, str string) uint64 {
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var seed string
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var ok bool
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if seed, ok = h.seeds[id]; !ok {
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seed = h.reseed(id)
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}
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return maphash.Bytes(h.hashSeed, []byte(seed+str))
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}
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}
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