Deserialization must fail if bytes remain after the last entry

tuple/include/tuple_sketch_impl.hpp

@@ -590,6 +590,11 @@ compact_tuple_sketch<S, A> compact_tuple_sketch<S, A>::deserialize(const void* b
       (*summary).~S();
     }
   }
+  const size_t bytes_consumed = ptr - base;
+  if (bytes_consumed != size) {
+    throw std::out_of_range("Unexpected buffer size: bytes consumed "
+        + std::to_string(bytes_consumed) + ", bytes available " + std::to_string(size));
+  }
   const bool is_ordered = flags_byte & (1 << flags::IS_ORDERED);
   return compact_tuple_sketch(is_empty, is_ordered, seed_hash, theta, std::move(entries));
 }

tuple/test/tuple_sketch_test.cpp

@@ -430,4 +430,16 @@ TEST_CASE("tuple sketch: deserialize bounds-checks each entry key", "[tuple_sket
                     std::out_of_range);
 }
 
+TEST_CASE("tuple sketch: deserialize rejects unconsumed bytes", "[tuple_sketch]") {
+  // A compact sketch serialized with a wider summary (double, 8 bytes) and then
+  // deserialized as a narrower summary (float, 4 bytes). The reader consumes less
+  // data than the entries occupy, so deserialization must fail if bytes remain 
+  // after the last entry.
+  auto update_sketch = update_tuple_sketch<double>::builder().build();
+  update_sketch.update(1, 1.0);
+  auto bytes = update_sketch.compact().serialize();
+  REQUIRE_THROWS_AS(compact_tuple_sketch<float>::deserialize(bytes.data(), bytes.size()),
+                    std::out_of_range);
+}
+
 } /* namespace datasketches */