[GLib] Add GArrowNullArrayBuilder

c_glib/arrow-glib/array-builder.cpp

@@ -153,6 +153,9 @@ G_BEGIN_DECLS
  *
  * You need to use array builder class to create a new array.
  *
+ * #GArrowNullArrayBuilder is the class to create a new
+ * #GArrowNullArray.
+ *
  * #GArrowBooleanArrayBuilder is the class to create a new
  * #GArrowBooleanArray.
  *
@@ -409,6 +412,79 @@ garrow_array_builder_finish(GArrowArrayBuilder *builder, GError **error)
 }
 
 
+G_DEFINE_TYPE(GArrowNullArrayBuilder,
+              garrow_null_array_builder,
+              GARROW_TYPE_ARRAY_BUILDER)
+
+static void
+garrow_null_array_builder_init(GArrowNullArrayBuilder *builder)
+{
+}
+
+static void
+garrow_null_array_builder_class_init(GArrowNullArrayBuilderClass *klass)
+{
+}
+
+/**
+ * garrow_null_array_builder_new:
+ *
+ * Returns: A newly created #GArrowNullArrayBuilder.
+ */
+GArrowNullArrayBuilder *
+garrow_null_array_builder_new(void)
+{
+  auto builder = garrow_array_builder_new(arrow::null(),
+                                          NULL,
+                                          "[null-array-builder][new]");
+  return GARROW_NULL_ARRAY_BUILDER(builder);
+}
+
+/**
+ * garrow_null_array_builder_append_null:
+ * @builder: A #GArrowNullArrayBuilder.
+ * @error: (nullable): Return location for a #GError or %NULL.
+ *
+ * Returns: %TRUE on success, %FALSE if there was an error.
+ *
+ * Since: 0.14.0
+ */
+gboolean
+garrow_null_array_builder_append_null(GArrowNullArrayBuilder *builder,
+                                      GError **error)
+{
+  return garrow_array_builder_append_null<arrow::NullBuilder *>
+    (GARROW_ARRAY_BUILDER(builder),
+     error,
+     "[null-array-builder][append-null]");
+}
+
+/**
+ * garrow_null_array_builder_append_nulls:
+ * @builder: A #GArrowNullArrayBuilder.
+ * @n: The number of null values to be appended.
+ * @error: (nullable): Return location for a #GError or %NULL.
+ *
+ * Append multiple nulls at once. It's more efficient than multiple
+ * `append_null()` calls.
+ *
+ * Returns: %TRUE on success, %FALSE if there was an error.
+ *
+ * Since: 0.14.0
+ */
+gboolean
+garrow_null_array_builder_append_nulls(GArrowNullArrayBuilder *builder,
+                                       gint64 n,
+                                       GError **error)
+{
+  return garrow_array_builder_append_nulls<arrow::NullBuilder *>
+    (GARROW_ARRAY_BUILDER(builder),
+     n,
+     error,
+     "[boolean-array-builder][append-nulls]");
+}
+
+
 G_DEFINE_TYPE(GArrowBooleanArrayBuilder,
               garrow_boolean_array_builder,
               GARROW_TYPE_ARRAY_BUILDER)
@@ -3890,6 +3966,9 @@ garrow_array_builder_new_raw(arrow::ArrayBuilder *arrow_builder,
 {
   if (type == G_TYPE_INVALID) {
     switch (arrow_builder->type()->id()) {
+    case arrow::Type::type::NA:
+      type = GARROW_TYPE_NULL_ARRAY_BUILDER;
+      break;
     case arrow::Type::type::BOOL:
       type = GARROW_TYPE_BOOLEAN_ARRAY_BUILDER;
       break;

c_glib/arrow-glib/array-builder.h

@@ -45,6 +45,59 @@ GArrowArray        *garrow_array_builder_finish   (GArrowArrayBuilder *builder,
                                                    GError **error);
 
 
+#define GARROW_TYPE_NULL_ARRAY_BUILDER       \
+  (garrow_null_array_builder_get_type())
+#define GARROW_NULL_ARRAY_BUILDER(obj)                                  \
+  (G_TYPE_CHECK_INSTANCE_CAST((obj),                                    \
+                              GARROW_TYPE_NULL_ARRAY_BUILDER,           \
+                              GArrowNullArrayBuilder))
+#define GARROW_NULL_ARRAY_BUILDER_CLASS(klass)                  \
+  (G_TYPE_CHECK_CLASS_CAST((klass),                             \
+                           GARROW_TYPE_NULL_ARRAY_BUILDER,      \
+                           GArrowNullArrayBuilderClass))
+#define GARROW_IS_NULL_ARRAY_BUILDER(obj)                               \
+  (G_TYPE_CHECK_INSTANCE_TYPE((obj),                                    \
+                              GARROW_TYPE_NULL_ARRAY_BUILDER))
+#define GARROW_IS_NULL_ARRAY_BUILDER_CLASS(klass)               \
+  (G_TYPE_CHECK_CLASS_TYPE((klass),                             \
+                           GARROW_TYPE_NULL_ARRAY_BUILDER))
+#define GARROW_NULL_ARRAY_BUILDER_GET_CLASS(obj)                \
+  (G_TYPE_INSTANCE_GET_CLASS((obj),                             \
+                             GARROW_TYPE_NULL_ARRAY_BUILDER,    \
+                             GArrowNullArrayBuilderClass))
+
+typedef struct _GArrowNullArrayBuilder         GArrowNullArrayBuilder;
+typedef struct _GArrowNullArrayBuilderClass    GArrowNullArrayBuilderClass;
+
+/**
+ * GArrowNullArrayBuilder:
+ *
+ * It wraps `arrow::NullBuilder`.
+ */
+struct _GArrowNullArrayBuilder
+{
+  /*< private >*/
+  GArrowArrayBuilder parent_instance;
+};
+
+struct _GArrowNullArrayBuilderClass
+{
+  GArrowArrayBuilderClass parent_class;
+};
+
+GType garrow_null_array_builder_get_type(void) G_GNUC_CONST;
+
+GArrowNullArrayBuilder *garrow_null_array_builder_new(void);
+
+/* TODO: should wrap AppendValue? */
+
+gboolean garrow_null_array_builder_append_null(GArrowNullArrayBuilder *builder,
+                                               GError **error);
+gboolean garrow_null_array_builder_append_nulls(GArrowNullArrayBuilder *builder,
+                                                gint64 n,
+                                                GError **error);
+
+
 #define GARROW_TYPE_BOOLEAN_ARRAY_BUILDER       \
   (garrow_boolean_array_builder_get_type())
 #define GARROW_BOOLEAN_ARRAY_BUILDER(obj)                               \

c_glib/test/helper/buildable.rb

@@ -17,6 +17,10 @@
 
 module Helper
   module Buildable
+    def build_null_array(values)
+      build_array(Arrow::NullArrayBuilder.new, values)
+    end
+
     def build_boolean_array(values)
       build_array(Arrow::BooleanArrayBuilder.new, values)
     end

c_glib/test/test-null-array.rb

@@ -16,18 +16,37 @@
 # under the License.
 
 class TestNullArray < Test::Unit::TestCase
+  include Helper::Buildable
+
+  def test_new
+    assert_equal(build_null_array([nil, nil, nil]),
+                 Arrow::NullArray.new(3))
+  end
+
   def test_length
-    array = Arrow::NullArray.new(3)
+    builder = Arrow::NullArrayBuilder.new
+    builder.append_null
+    builder.append_null
+    builder.append_null
+    array = builder.finish
     assert_equal(3, array.length)
   end
 
   def test_n_nulls
-    array = Arrow::NullArray.new(3)
+    builder = Arrow::NullArrayBuilder.new
+    builder.append_null
+    builder.append_null
+    builder.append_null
+    array = builder.finish
     assert_equal(3, array.n_nulls)
   end
 
   def test_slice
-    array = Arrow::NullArray.new(3)
+    builder = Arrow::NullArrayBuilder.new
+    builder.append_null
+    builder.append_null
+    builder.append_null
+    array = builder.finish
     assert_equal(2, array.slice(1, 2).length)
   end
 end