cache: move package to plumbing

Because cache package is only intended to be used at internal level, we move it to the plumbing package.

1 files changed, 68 insertions, 0 deletions

diff --git a/plumbing/cache/object.go b/plumbing/cache/object.go
new file mode 100644
index 0000000..47e390b
--- /dev/null
+++ b/plumbing/cache/object.go
@@ -0,0 +1,68 @@
+package cache
+
+import "srcd.works/go-git.v4/plumbing"
+
+const (
+	initialQueueSize = 20
+	MaxSize          = 10 * MiByte
+)
+
+type ObjectFIFO struct {
+	objects map[plumbing.Hash]plumbing.EncodedObject
+	order   *queue
+
+	maxSize    int64
+	actualSize int64
+}
+
+// NewObjectFIFO returns an Object cache that keeps the newest objects that fit
+// into the specific memory size
+func NewObjectFIFO(size int64) *ObjectFIFO {
+	return &ObjectFIFO{
+		objects: make(map[plumbing.Hash]plumbing.EncodedObject),
+		order:   newQueue(initialQueueSize),
+		maxSize: size,
+	}
+}
+
+// Add adds a new object to the cache. If the object size is greater than the
+// cache size, the object is not added.
+func (c *ObjectFIFO) Add(o plumbing.EncodedObject) {
+	// if the size of the object is bigger or equal than the cache size,
+	// skip it
+	if o.Size() >= c.maxSize {
+		return
+	}
+
+	// if the object is into the cache, do not add it again
+	if _, ok := c.objects[o.Hash()]; ok {
+		return
+	}
+
+	// delete the oldest object if cache is full
+	if c.actualSize >= c.maxSize {
+		h := c.order.Pop()
+		o := c.objects[h]
+		if o != nil {
+			c.actualSize -= o.Size()
+			delete(c.objects, h)
+		}
+	}
+
+	c.objects[o.Hash()] = o
+	c.order.Push(o.Hash())
+	c.actualSize += o.Size()
+}
+
+// Get returns an object by his hash. If the object is not found in the cache, it
+// returns nil
+func (c *ObjectFIFO) Get(k plumbing.Hash) plumbing.EncodedObject {
+	return c.objects[k]
+}
+
+// Clear the content of this object cache
+func (c *ObjectFIFO) Clear() {
+	c.objects = make(map[plumbing.Hash]plumbing.EncodedObject)
+	c.order = newQueue(initialQueueSize)
+	c.actualSize = 0
+}