vendor: add github.com/die-net/lrucache

vendor/github.com/die-net/lrucache/twotier/twotier.go

@@ -0,0 +1,57 @@
+// Package twotier provides a wrapper for two httpcache.Cache instances,
+// allowing you to use both a small and fast cache for popular objects and
+// fall back to a larger and slower cache for less popular ones.
+package twotier
+
+import (
+	"github.com/gregjones/httpcache"
+)
+
+// TwoTier creates a two-tiered cache out of two httpcache.Cache instances.
+// Reads are favored from first, and writes affect both first and second.
+type TwoTier struct {
+	first  httpcache.Cache
+	second httpcache.Cache
+}
+
+// New creates a TwoTier. Both first and second must be non-nil.
+func New(first httpcache.Cache, second httpcache.Cache) *TwoTier {
+	if first == nil || second == nil || first == second {
+		return nil
+	}
+	return &TwoTier{first: first, second: second}
+}
+
+// Get returns the []byte representation of a cached response and a bool set
+// to true if the key was found.  It tries the first tier cache, and if
+// that's not successful, copies the result from the second tier into the
+// first tier.
+func (c *TwoTier) Get(key string) ([]byte, bool) {
+	if value, ok := c.first.Get(key); ok {
+		return value, true
+	}
+
+	value, ok := c.second.Get(key)
+	if !ok {
+		return nil, false
+	}
+
+	c.first.Set(key, value)
+
+	return value, true
+}
+
+// Set stores the []byte representation of a response for a given key into
+// the second tier cache, and deletes the cache entry from the first tier
+// cache.
+func (c *TwoTier) Set(key string, value []byte) {
+	c.second.Set(key, value)
+	c.first.Delete(key)
+}
+
+// Delete removes the value associated with a key from both the first and
+// second tier caches.
+func (c *TwoTier) Delete(key string) {
+	c.second.Delete(key)
+	c.first.Delete(key)
+}