Add getter and setter for the indent value of Ox::Builder (#296)

* Add Ox::Builder#indent

This getter return the indent option of the builder.

* Add Ox::Builder#indent=

With this setter the indentation level can be changes dynamically. It
allows to build XML where some of the nodes are formatted inline within
the parent node.
This is useful for nodes that consider all spacing and line-breaking as
part of the value of the node's text.

ext/ox/builder.c

@@ -881,6 +881,35 @@ builder_column(VALUE self) {
     return LONG2NUM(((Builder)DATA_PTR(self))->col);
 }
 
+/* call-seq: indent()
+ *
+ * Returns the indentation level
+ */
+static VALUE
+builder_get_indent(VALUE self) {
+    return INT2NUM(((Builder)DATA_PTR(self))->indent);
+}
+
+/* call-seq: indent=(indent)
+ *
+ * Sets the indentation level
+ *
+ * - +indent+ (Fixnum) indentaion level, negative values excludes terminating newline
+ */
+static VALUE
+builder_set_indent(VALUE self, VALUE indent) {
+#ifdef RUBY_INTEGER_UNIFICATION
+    if (rb_cInteger != rb_obj_class(indent)) {
+#else
+    if (rb_cFixnum != rb_obj_class(indent)) {
+#endif
+      rb_raise(ox_parse_error_class, "indent must be a fixnum.\n");
+    }
+
+    ((Builder)DATA_PTR(self))->indent = NUM2INT(indent);
+    return Qnil;
+}
+
 /* call-seq: pos()
  *
  * Returns the number of bytes written.
@@ -940,4 +969,6 @@ ox_init_builder(VALUE ox) {
     rb_define_method(builder_class, "line", builder_line, 0);
     rb_define_method(builder_class, "column", builder_column, 0);
     rb_define_method(builder_class, "pos", builder_pos, 0);
+    rb_define_method(builder_class, "indent", builder_get_indent, 0);
+    rb_define_method(builder_class, "indent=", builder_set_indent, 1);
 }

test/tests.rb

@@ -1471,6 +1471,7 @@ def test_prepend_child_when_nodes_not_empty
 
   def test_builder
     b = Ox::Builder.new(:indent => 2)
+    assert_equal(2, b.indent())
     assert_equal(1, b.line())
     assert_equal(1, b.column())
     assert_equal(0, b.pos())
@@ -1510,6 +1511,31 @@ def test_builder
 |, xml)
   end
 
+  def test_builder_set_indent
+    b = Ox::Builder.new(:indent => 2)
+    assert_equal(2, b.indent())
+    b.instruct(:xml, :version => '1.0', :encoding => 'UTF-8')
+    b.element('one')
+    b.element('two')
+    b.indent = 0
+    b.text('Sample ')
+    b.element('three', :a => 'ack')
+    b.text('sample')
+    b.pop() # </three>
+    b.pop() # </two>
+    b.indent = 2
+    b.element('four')
+    b.pop()
+    b.close()
+    xml = b.to_s
+    assert_equal(%|<?xml version="1.0" encoding="UTF-8"?>
+<one>
+  <two>Sample <three a="ack">sample</three></two>
+  <four/>
+</one>
+|, xml)
+  end
+
   def test_builder_file
     filename = File.join(File.dirname(__FILE__), 'create_file_test.xml')
     b = Ox::Builder.file(filename, :indent => 2)