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package atomic
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import (
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	"sync"
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	"github.com/zeebo/xxh3"
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)
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const shardSize = 128
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type KeyedRWMutex struct {
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	noCopy
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	mutexes [shardSize]sync.RWMutex
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}
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func NewKeyedRWMutex() *KeyedRWMutex {
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	return &KeyedRWMutex{}
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}
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func (m *KeyedRWMutex) obtain(key string) *sync.RWMutex {
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	i := xxh3.HashString(key) % shardSize
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	return &m.mutexes[i]
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}
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func (m *KeyedRWMutex) Lock(key string) func() {
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	mu := m.obtain(key)
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	mu.Lock()
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	return mu.Unlock
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}
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func (m *KeyedRWMutex) RLock(key string) func() {
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	mu := m.obtain(key)
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	mu.RLock()
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	return mu.RUnlock
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}