LindaSummer commented on code in PR #3268:
URL: https://github.com/apache/kvrocks/pull/3268#discussion_r2579845952
##########
src/types/redis_tdigest.h:
##########
@@ -33,6 +33,101 @@
#include "tdigest.h"
namespace redis {
+
+// TODO: It should be replaced by a iteration of the rocksdb iterator
+template <bool Reverse>
+class DummyCentroids {
+ public:
+ DummyCentroids(const TDigestMetadata& meta_data, const
std::vector<Centroid>& centroids)
+ : meta_data_(meta_data), centroids_(centroids) {}
+ class Iterator {
+ public:
+ using IterType = std::conditional_t<Reverse,
std::vector<Centroid>::const_reverse_iterator,
+ std::vector<Centroid>::const_iterator>;
+ Iterator(IterType iter, const std::vector<Centroid>& centroids) :
iter_(iter), centroids_(centroids) {}
+ std::unique_ptr<Iterator> Clone() const {
+ if (iter_ != getCendIter(centroids_)) {
+ return std::make_unique<Iterator>(
+ std::next(getCbeginIter(centroids_),
std::distance(getCbeginIter(centroids_), iter_)), centroids_);
+ }
+ return std::make_unique<Iterator>(getCendIter(centroids_), centroids_);
+ }
+ bool Next() {
+ if (Valid()) {
+ std::advance(iter_, 1);
+ }
+ return iter_ != getCendIter(centroids_);
+ }
+
+ // The Prev function can only be called for item is not cend,
+ // because we must guarantee the iterator to be inside the valid range
before iteration.
+ bool Prev() {
+ if (Valid() && iter_ != getCendIter(centroids_)) {
+ std::advance(iter_, -1);
+ }
+ return Valid();
+ }
+ bool Valid() const { return iter_ != getCendIter(centroids_); }
+ StatusOr<Centroid> GetCentroid() const {
+ if (iter_ == getCendIter(centroids_)) {
+ return {::Status::NotOK, "invalid iterator during decoding tdigest
centroid"};
+ }
+ return *iter_;
+ }
+
+ private:
+ IterType iter_;
+ const std::vector<Centroid>& centroids_;
+ template <typename Container>
+ decltype(auto) getCbeginIter(const Container& centroids) const {
+ if constexpr (Reverse) {
+ return centroids.crbegin();
+ } else {
+ return centroids.cbegin();
+ }
+ }
+
+ template <typename Container>
+ decltype(auto) getCendIter(const Container& centroids) const {
+ if constexpr (Reverse) {
+ return centroids.crend();
+ } else {
+ return centroids.cend();
+ }
+ }
+ };
+
+ std::unique_ptr<Iterator> Begin() const {
+ if constexpr (Reverse) {
Review Comment:
I think the getbegin and getend are both stateless, static is ok.
maybe they could be a free inline function protected by a `detail` private
namespace if you prefer this way.
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