Simple in memory Tristate (miss/yes/no) cache

tristate.go

package tristate

import "sync"

// State for a tristate cache
type State int

// cache State contants
const (
	Miss State = iota
	Yes
	No
)

// Cache interface that satisfies the conditions
// of a tri-state (Miss/Yes/No)
type Cache interface {
	Get(key interface{}) State
	SetYes(keys ...interface{})
	SetNo(keys ...interface{})
}

// NewCache returns a tristate cache
func NewCache(n int) Cache {
	return &triStateCache{
		m:     sync.RWMutex{},
		cache: make(map[interface{}]State, n),
	}
}

// triStateCache is a simple yes/no/miss im memory cache
type triStateCache struct {
	m     sync.RWMutex
	cache map[interface{}]State
}

// is it in the cache
func (tsc *triStateCache) Get(id interface{}) State {
	tsc.m.RLock()
	defer tsc.m.RUnlock()
	if _, ok := tsc.cache[id]; !ok {
		return Miss
	}
	return tsc.cache[id]
}

func (tsc *triStateCache) SetYes(ids ...interface{}) {
	tsc.m.Lock()
	defer tsc.m.Unlock()
	for _, i := range ids {
		tsc.cache[i] = Yes
	}
}

func (tsc *triStateCache) SetNo(ids ...interface{}) {
	tsc.m.Lock()
	defer tsc.m.Unlock()
	for _, i := range ids {
		tsc.cache[i] = No
	}
}