Get the world name (#1027)

Signed-off-by: ahcorde <[email protected]>

include/sdf/Root.hh

@@ -18,6 +18,7 @@
 #define SDF_ROOT_HH_
 
 #include <string>
+#include <vector>
 #include <gz/utils/ImplPtr.hh>
 
 #include "sdf/OutputConfig.hh"
@@ -58,6 +59,17 @@ namespace sdf
     /// \brief Default constructor
     public: Root();
 
+    /// \brief Get the name of the world without loading the entire world
+    /// Users shouldn't normally need to use this API.
+    /// This doesn't load the world, it might return the world name even if the
+    /// file is not a valid SDFormat file.
+    /// \param[in] _filename Name of the SDF file to parse.
+    /// \param[out] _worldNames A vector with world names
+    /// \return Errors, which is a vector of Error objects. Each Error includes
+    /// an error code and message. An empty vector indicates no error.
+    public: Errors WorldNamesFromFile(const std::string &_filename,
+                                     std::vector<std::string> &_worldNames);
+
     /// \brief Parse the given SDF file, and generate objects based on types
     /// specified in the SDF file.
     /// \param[in] _filename Name of the SDF file to parse.

src/Root.cc

@@ -140,6 +140,45 @@ Root::Root()
 {
 }
 
+Errors Root::WorldNamesFromFile(
+  const std::string &_filename,
+  std::vector<std::string> &_worldNames)
+{
+  Errors errors;
+
+  tinyxml2::XMLDocument doc;
+  if(doc.LoadFile(_filename.c_str()))
+  {
+    errors.push_back({ErrorCode::FILE_READ,
+                      "Unable to load file[" + _filename + "]:" +
+                      doc.ErrorStr()});
+    return errors;
+  }
+  tinyxml2::XMLElement * pRootElement = doc.RootElement();
+  if (nullptr != pRootElement)
+  {
+    tinyxml2::XMLElement * pworld = pRootElement->FirstChildElement("world");
+
+    while(pworld)
+    {
+      _worldNames.push_back(pworld->Attribute("name"));
+      pworld = pworld->NextSiblingElement("world");
+    }
+
+    if (_worldNames.size() == 0)
+    {
+      errors.push_back({ErrorCode::ELEMENT_INVALID,
+                        "Failed to read the world tag."});
+    }
+  }
+  else
+  {
+    errors.push_back({ErrorCode::ELEMENT_INVALID,
+                      "Failed to read the root."});
+  }
+  return errors;
+}
+
 /////////////////////////////////////////////////
 Errors Root::Load(const std::string &_filename)
 {

src/Root_TEST.cc

@@ -26,6 +26,7 @@
 #include "sdf/World.hh"
 #include "sdf/Frame.hh"
 #include "sdf/Root.hh"
+#include "test_config.hh"
 
 /////////////////////////////////////////////////
 TEST(DOMRoot, Construction)
@@ -65,6 +66,29 @@ TEST(DOMRoot, MoveAssignmentOperator)
   EXPECT_EQ("test_root", root2.Version());
 }
 
+TEST(DOMRoot, WorldNamesFromFile)
+{
+  const auto path = sdf::testing::TestFile("sdf", "basic_shapes.sdf");
+  sdf::Root root;
+  std::vector<std::string> worldNames;
+  auto errors = root.WorldNamesFromFile(path, worldNames);
+  EXPECT_TRUE(errors.empty());
+  EXPECT_EQ(1u, worldNames.size());
+  EXPECT_EQ("shapes_world", worldNames[0]);
+
+  worldNames.clear();
+  const auto path2 = sdf::testing::TestFile("sdf", "empty_invalid.sdf");
+  errors = root.WorldNamesFromFile(path2, worldNames);
+  EXPECT_EQ(0u, worldNames.size());
+  EXPECT_FALSE(errors.empty());
+
+  worldNames.clear();
+  const auto path3 = sdf::testing::TestFile("sdf", "invalid_file_name.sdf");
+  errors = root.WorldNamesFromFile(path3, worldNames);
+  EXPECT_EQ(0u, worldNames.size());
+  EXPECT_FALSE(errors.empty());
+}
+
 /////////////////////////////////////////////////
 TEST(DOMRoot, StringModelSdfParse)
 {