fixed serialization of empty sketch as bytes

apache · Feb 21, 2024 · 7f0c235 · 7f0c235
1 parent 1b0ab18
commit 7f0c235
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Showing 2 changed files with 22 additions and 1 deletion.
diff --git a/tdigest/include/tdigest_impl.hpp b/tdigest/include/tdigest_impl.hpp
@@ -320,7 +320,7 @@ template<typename T, typename A>
 auto tdigest<T, A>::serialize(unsigned header_size_bytes) const -> vector_bytes {
   const_cast<tdigest*>(this)->merge_buffered(); // side effect
   const uint8_t preamble_longs = is_empty() ? PREAMBLE_LONGS_EMPTY : PREAMBLE_LONGS_NON_EMPTY;
-  const size_t size_bytes = preamble_longs * sizeof(uint64_t) + sizeof(T) * 2 + sizeof(centroid) * centroids_.size();
+  const size_t size_bytes = preamble_longs * sizeof(uint64_t) + (is_empty() ? 0 : sizeof(T) * 2 + sizeof(centroid) * centroids_.size());
   vector_bytes bytes(size_bytes, 0, allocator_);
   uint8_t* ptr = bytes.data() + header_size_bytes;
 

diff --git a/tdigest/test/tdigest_test.cpp b/tdigest/test/tdigest_test.cpp
@@ -204,6 +204,27 @@ TEST_CASE("serialize deserialize bytes non empty", "[tdigest]") {
   REQUIRE(td.get_quantile(0.5) == deserialized_td.get_quantile(0.5));
 }
 
+TEST_CASE("serialize deserialize steam and bytes equivalence empty", "[tdigest]") {
+  tdigest<double> td(100);
+  std::stringstream s(std::ios::in | std::ios::out | std::ios::binary);
+  td.serialize(s);
+  auto bytes = td.serialize();
+
+  REQUIRE(bytes.size() == static_cast<size_t>(s.tellp()));
+  for (size_t i = 0; i < bytes.size(); ++i) {
+    REQUIRE(((char*)bytes.data())[i] == (char)s.get());
+  }
+
+  s.seekg(0); // rewind
+  auto deserialized_td1 = tdigest<double>::deserialize(s);
+  auto deserialized_td2 = tdigest<double>::deserialize(bytes.data(), bytes.size());
+  REQUIRE(bytes.size() == static_cast<size_t>(s.tellg()));
+
+  REQUIRE(deserialized_td1.get_k() == deserialized_td2.get_k());
+  REQUIRE(deserialized_td1.get_total_weight() == deserialized_td2.get_total_weight());
+  REQUIRE(deserialized_td1.is_empty() == deserialized_td2.is_empty());
+}
+
 TEST_CASE("serialize deserialize steam and bytes equivalence", "[tdigest]") {
   tdigest<double> td(100);
   for (int i = 0; i < 1000; ++i) td.update(i);