add cache and start using it in repo

1 files changed, 58 insertions, 0 deletions

diff --git a/cache/cache.go b/cache/cache.go
new file mode 100644
index 0000000..ff2c279
--- /dev/null
+++ b/cache/cache.go
@@ -0,0 +1,58 @@
+package cache
+
+import "sync"
+
+type Cacher interface {
+	Get(key interface{}) (value []byte, exists bool)
+	Set(key interface{}, value []byte)
+	Len() int
+}
+
+type FifoCache struct {
+	head, tail *fifoCacheEntry
+	data       map[interface{}][]byte
+	capacity   int
+	mutex      sync.RWMutex
+}
+
+type fifoCacheEntry struct {
+	Key  interface{}
+	Next *fifoCacheEntry
+}
+
+func NewFifoCache(capacity int) *FifoCache {
+	return &FifoCache{data: make(map[interface{}][]byte, capacity), capacity: capacity}
+}
+
+func (c *FifoCache) Get(key interface{}) (value []byte, exists bool) {
+	c.mutex.RLock()
+	defer c.mutex.RUnlock()
+	value, exists = c.data[key]
+	return
+}
+
+func (c *FifoCache) Set(key interface{}, value []byte) {
+	c.mutex.Lock()
+	defer c.mutex.Unlock()
+	if len(c.data) == c.capacity {
+		// Evict first entry
+		evicted := c.head
+		c.head = evicted.Next
+		delete(c.data, evicted.Key)
+	}
+	entry := &fifoCacheEntry{Key: key}
+	if c.head == nil {
+		c.head = entry
+	}
+	if c.tail == nil {
+		c.tail = entry
+	} else {
+		c.tail.Next = entry
+		c.tail = entry
+	}
+	c.data[key] = value
+}
+
+func (c *FifoCache) Len() int {
+	return len(c.data)
+}