d_cache.go

package gossipcache

import (
	"github.com/golang/groupcache/lru"
	"sync"
)

// cache is a wrapper around an *lru.Cache that adds synchronization,
// makes values always be ByteView, and counts the size of all keys and
// values.
type cache struct {
	mu         sync.RWMutex
	nbytes     int64 // of all keys and values
	lru        *lru.Cache
	nhit, nget int64
	nevict     int64 // number of evictions
}

func (c *cache) add(key string, value ByteView) {
	c.mu.Lock()
	defer c.mu.Unlock()
	if c.lru == nil {
		c.lru = &lru.Cache{
			OnEvicted: func(key lru.Key, value interface{}) {
				val := value.(ByteView)
				c.nbytes -= int64(len(key.(string))) + int64(val.Len())
				c.nevict++
			},
		}
	}
	c.lru.Add(key, value)
	c.nbytes += int64(len(key)) + int64(value.Len())
}

func (c *cache) get(key string) (value ByteView, ok bool) {
	c.mu.Lock()
	defer c.mu.Unlock()
	c.nget++
	if c.lru == nil {
		return
	}
	vi, ok := c.lru.Get(key)
	if !ok {
		return
	}
	c.nhit++
	return vi.(ByteView), true
}

func (c *cache) bytes() int64 {
	c.mu.RLock()
	defer c.mu.RUnlock()
	return c.nbytes
}

func (c *cache) removeOldest() {
	c.mu.Lock()
	defer c.mu.Unlock()
	if c.lru != nil {
		c.lru.RemoveOldest()
	}
}