Add redis support for distributed caching

vendor/github.com/alicebob/miniredis/v2/hll.go

@@ -0,0 +1,42 @@
+package miniredis
+
+import (
+	"github.com/alicebob/miniredis/v2/hyperloglog"
+)
+
+type hll struct {
+	inner *hyperloglog.Sketch
+}
+
+func newHll() *hll {
+	return &hll{
+		inner: hyperloglog.New14(),
+	}
+}
+
+// Add returns true if cardinality has been changed, or false otherwise.
+func (h *hll) Add(item []byte) bool {
+	return h.inner.Insert(item)
+}
+
+// Count returns the estimation of a set cardinality.
+func (h *hll) Count() int {
+	return int(h.inner.Estimate())
+}
+
+// Merge merges the other hll into original one (not making a copy but doing this in place).
+func (h *hll) Merge(other *hll) {
+	_ = h.inner.Merge(other.inner)
+}
+
+// Bytes returns raw-bytes representation of hll data structure.
+func (h *hll) Bytes() []byte {
+	dataBytes, _ := h.inner.MarshalBinary()
+	return dataBytes
+}
+
+func (h *hll) copy() *hll {
+	return &hll{
+		inner: h.inner.Clone(),
+	}
+}