feat: HLL - expose get_lg_config_k for Sketch & Union

Author: ovr

datasketches-cpp/hll.cpp

@@ -36,6 +36,10 @@ datasketches::target_hll_type OpaqueHLLSketch::get_target_type() const {
   return this->inner_.get_target_type();
 }
 
+uint8_t OpaqueHLLSketch::get_lg_config_k() const {
+  return this->inner_.get_lg_config_k();
+}
+
 std::unique_ptr<std::vector<uint8_t>> OpaqueHLLSketch::serialize() const {
   // TODO: could use a custom streambuf to avoid the
   // stream -> vec copy https://stackoverflow.com/a/13059195/1779853
@@ -80,6 +84,10 @@ datasketches::target_hll_type OpaqueHLLUnion::get_target_type() const {
   return this->inner_.get_target_type();
 }
 
+uint8_t OpaqueHLLUnion::get_lg_config_k() const {
+  return this->inner_.get_lg_config_k();
+}
+
 std::unique_ptr<OpaqueHLLUnion> new_opaque_hll_union(uint8_t lg_max_k) {
   return std::unique_ptr<OpaqueHLLUnion>(new OpaqueHLLUnion{ lg_max_k });
 }

datasketches-cpp/hll.hpp

@@ -20,6 +20,7 @@ class OpaqueHLLSketch {
   friend std::unique_ptr<OpaqueHLLSketch> deserialize_opaque_hll_sketch(rust::Slice<const uint8_t> buf);
   OpaqueHLLSketch(unsigned lg_k, datasketches::target_hll_type tgt_type);
   datasketches::target_hll_type get_target_type() const;
+  uint8_t get_lg_config_k() const;
 private:
   OpaqueHLLSketch(datasketches::hll_sketch&& hll);
   OpaqueHLLSketch(std::istream& is);
@@ -36,6 +37,7 @@ class OpaqueHLLUnion {
   void merge(std::unique_ptr<OpaqueHLLSketch> to_add);
   OpaqueHLLUnion(uint8_t lg_max_k);
   datasketches::target_hll_type get_target_type() const;
+  uint8_t get_lg_config_k() const;
 private:
   datasketches::hll_union inner_;
 };

src/bridge.rs

@@ -56,6 +56,7 @@ pub(crate) mod ffi {
         pub(crate) fn update_u64(self: Pin<&mut OpaqueHLLSketch>, value: u64);
         pub(crate) fn serialize(self: &OpaqueHLLSketch) -> UniquePtr<CxxVector<u8>>;
         pub(crate) fn get_target_type(self: &OpaqueHLLSketch) -> target_hll_type;
+        pub(crate) fn get_lg_config_k(self: &OpaqueHLLSketch) -> u8;
 
         pub(crate) fn new_opaque_hll_sketch(
             lg_k: u32,
@@ -74,6 +75,7 @@ pub(crate) mod ffi {
         ) -> UniquePtr<OpaqueHLLSketch>;
         pub(crate) fn merge(self: Pin<&mut OpaqueHLLUnion>, to_add: UniquePtr<OpaqueHLLSketch>);
         pub(crate) fn get_target_type(self: &OpaqueHLLUnion) -> target_hll_type;
+        pub(crate) fn get_lg_config_k(self: &OpaqueHLLUnion) -> u8;
 
         include!("dsrs/datasketches-cpp/theta.hpp");
 

src/wrapper/hll.rs

@@ -57,6 +57,11 @@ impl HLLSketch {
         self.inner.get_target_type()
     }
 
+    /// Returns sketch's configured lg_k value
+    pub fn get_lg_config_k(&self) -> u8 {
+        self.inner.get_lg_config_k()
+    }
+
     pub fn serialize(&self) -> impl AsRef<[u8]> {
         struct UPtrVec(cxx::UniquePtr<cxx::CxxVector<u8>>);
         impl AsRef<[u8]> for UPtrVec {
@@ -99,6 +104,11 @@ impl HLLUnion {
         self.inner.get_target_type()
     }
 
+    /// Returns union's configured lg_k value
+    pub fn get_lg_config_k(&self) -> u8 {
+        self.inner.get_lg_config_k()
+    }
+
     /// Retrieve the current unioned sketch as a copy.
     pub fn sketch(&self, tgt_type: HLLType) -> HLLSketch {
         HLLSketch {
@@ -153,6 +163,7 @@ mod tests {
     #[test]
     fn hll_simple_test_hll4() {
         let mut hh = HLLSketch::new(12, HLLType::HLL_4);
+        assert_eq!(hh.get_lg_config_k(), 12);
         assert_eq!(hh.get_target_type(), HLLType::HLL_4);
 
         assert_eq!(hh.estimate(), 0.0);
@@ -171,6 +182,7 @@ mod tests {
     #[test]
     fn hll_simple_test_hll6() {
         let mut hh = HLLSketch::new(12, HLLType::HLL_6);
+        assert_eq!(hh.get_lg_config_k(), 12);
         assert_eq!(hh.get_target_type(), HLLType::HLL_6);
 
         assert_eq!(hh.estimate(), 0.0);
@@ -189,6 +201,7 @@ mod tests {
     #[test]
     fn hll_simple_test_hll8() {
         let mut hh = HLLSketch::new(12, HLLType::HLL_8);
+        assert_eq!(hh.get_lg_config_k(), 12);
         assert_eq!(hh.get_target_type(), HLLType::HLL_8);
 
         assert_eq!(hh.estimate(), 0.0);
@@ -211,6 +224,7 @@ mod tests {
 
         let mut union = HLLUnion::new(12);
         assert_eq!(union.get_target_type(), HLLType::HLL_8);
+        assert_eq!(union.get_lg_config_k(), 12);
 
         union.merge(hll);
         union.merge(HLLSketch::new(12, HLLType::HLL_4));