make a value copy using the API

1 files changed, 45 insertions, 3 deletions

diff --git a/eval/src/vespa/eval/eval/value.cpp b/eval/src/vespa/eval/eval/value.cpp
index 7dcd04c8ab2..bfa77d1a604 100644
--- a/eval/src/vespa/eval/eval/value.cpp
+++ b/eval/src/vespa/eval/eval/value.cpp
@@ -64,12 +64,54 @@ ValueType ScalarValue<T>::_type = ValueType::make_type(get_cell_type<T>(), {});
 template class ScalarValue<double>;
 template class ScalarValue<float>;
 
+namespace {
+
+struct CopyValue {
+    template <typename CT>
+    static std::unique_ptr<Value> invoke(const Value &value,
+                                         const ValueType &type,
+                                         const ValueBuilderFactory &factory)
+    {
+        size_t num_mapped = type.count_mapped_dimensions();
+        size_t dense_size = type.dense_subspace_size();
+        const auto & idx = value.index();
+        auto input_cells = value.cells().typify<CT>();
+        auto builder = factory.create_value_builder<CT>(type, num_mapped, dense_size, idx.size());
+        std::vector<string_id> addr(num_mapped);
+        if (num_mapped == 0) {
+            assert(idx.size() == 1);
+            auto array_ref = builder->add_subspace(addr);
+            for (size_t i = 0; i < dense_size; ++i) {
+                array_ref[i] = input_cells[i];
+            }
+        } else {
+            auto view = idx.create_view({});
+            view->lookup({});
+            std::vector<string_id*> addr_fetch;
+            addr_fetch.reserve(num_mapped);
+            for (auto & label : addr) {
+                addr_fetch.push_back(&label);
+            }
+            size_t subspace_idx;
+            while (view->next_result(addr_fetch, subspace_idx)) {
+                auto array_ref = builder->add_subspace(addr);
+                for (size_t i = 0; i < dense_size; ++i) {
+                    array_ref[i] = input_cells[(dense_size * subspace_idx) + i];
+                }
+            }
+        }
+        return builder->build(std::move(builder));
+    }
+};
+
+} // namespace <unnamed>
+
 std::unique_ptr<Value>
 ValueBuilderFactory::copy(const Value &value) const
 {
-    nbostream stream;
-    encode_value(value, stream);
-    return decode_value(stream, *this);
+    const auto & type = value.type();
+    return typify_invoke<1,TypifyCellType,CopyValue>(type.cell_type(),
+                                                     value, type, *this);
 }
 
 } // namespace vespalib::eval