🦈🏠🐜❗ Initial Commit ❗🐜🦈🏠

http/cache.go

@@ -0,0 +1,99 @@
+package http
+
+import (
+	"container/list"
+	"fmt"
+	"hash/fnv"
+	"net"
+	"sync"
+)
+
+type Cache struct {
+	capacity  int
+	mu        sync.RWMutex
+	entries   map[uint64]*list.Element
+	values    *list.List
+	evictions uint64
+}
+
+type CacheStats struct {
+	Capacity  int
+	Size      int
+	Evictions uint64
+}
+
+func NewCache(capacity int) *Cache {
+	if capacity < 0 {
+		capacity = 0
+	}
+	return &Cache{
+		capacity: capacity,
+		entries:  make(map[uint64]*list.Element),
+		values:   list.New(),
+	}
+}
+
+func key(ip net.IP) uint64 {
+	h := fnv.New64a()
+	h.Write(ip)
+	return h.Sum64()
+}
+
+func (c *Cache) Set(ip net.IP, resp Response) {
+	if c.capacity == 0 {
+		return
+	}
+	k := key(ip)
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	minEvictions := len(c.entries) - c.capacity + 1
+	if minEvictions > 0 { // At or above capacity. Shrink the cache
+		evicted := 0
+		for el := c.values.Front(); el != nil && evicted < minEvictions; {
+			value := el.Value.(Response)
+			delete(c.entries, key(value.IP))
+			next := el.Next()
+			c.values.Remove(el)
+			el = next
+			evicted++
+		}
+		c.evictions += uint64(evicted)
+	}
+	current, ok := c.entries[k]
+	if ok {
+		c.values.Remove(current)
+	}
+	c.entries[k] = c.values.PushBack(resp)
+}
+
+func (c *Cache) Get(ip net.IP) (Response, bool) {
+	k := key(ip)
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	r, ok := c.entries[k]
+	if !ok {
+		return Response{}, false
+	}
+	return r.Value.(Response), true
+}
+
+func (c *Cache) Resize(capacity int) error {
+	if capacity < 0 {
+		return fmt.Errorf("invalid capacity: %d\n", capacity)
+	}
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	c.capacity = capacity
+	c.evictions = 0
+	return nil
+}
+
+func (c *Cache) Stats() CacheStats {
+	c.mu.RLock()
+	defer c.mu.RUnlock()
+	return CacheStats{
+		Size:      len(c.entries),
+		Capacity:  c.capacity,
+		Evictions: c.evictions,
+	}
+}