Introduce a cache to improve performance of construction of SDFormat (#1610)

arjo129 · Addisu Z. Taddese · web-flow · commit 403d96a76e74 · 2026-01-02T10:24:14.000-06:00
Reduces load times significantly as it caches the first parse of the spec so that it does not need to be reparsed during construction through static initiallization of a cache.

---------

Signed-off-by: Arjo Chakravarty &lt;arjo@openrobotics.org&gt;
Signed-off-by: Arjo Chakravarty &lt;arjo129@gmail.com&gt;
Co-authored-by: Addisu Z. Taddese &lt;addisu@openrobotics.org&gt;
diff --git a/include/sdf/SDFImpl.hh b/include/sdf/SDFImpl.hh
@@ -166,6 +166,8 @@ namespace sdf
   class SDFORMAT_VISIBLE SDF
   {
     public: SDF();
+    public: SDF(const SDF& other);
+    public: SDF& operator=(const SDF& other);
     /// \brief Destructor
     public: ~SDF();
     public: void PrintDescription();
diff --git a/src/Root.cc b/src/Root.cc
@@ -14,6 +14,7 @@
  * limitations under the License.
  *
 */
+#include <gz/utils/NeverDestroyed.hh>
 #include <string>
 #include <variant>
 #include <vector>
@@ -24,6 +25,7 @@
 #include "sdf/Light.hh"
 #include "sdf/Model.hh"
 #include "sdf/Root.hh"
+#include "sdf/SDFImpl.hh"
 #include "sdf/Types.hh"
 #include "sdf/World.hh"
 #include "sdf/parser.hh"
@@ -34,6 +36,18 @@
 
 using namespace sdf;
 
+/// \brief A cache for SDF Parsing
+struct SdfCache {
+
+  /// \brief Constructor.
+  SdfCache(): sdfParsed(new SDF()) {
+    init(this->sdfParsed);
+  }
+
+  /// \brief The parsed SDF Spec
+  SDFPtr sdfParsed;
+};
+
 /// \brief Private data for sdf::Root
 class sdf::Root::Implementation
 {
@@ -217,9 +231,9 @@ Errors Root::LoadSdfString(const std::string &_sdf)
 Errors Root::LoadSdfString(const std::string &_sdf, const ParserConfig &_config)
 {
   Errors errors;
-  SDFPtr sdfParsed(new SDF());
-  init(sdfParsed);
-
+  // Make a copy of the cached structure
+  static gz::utils::NeverDestroyed<SdfCache> cache;
+  SDFPtr sdfParsed = std::make_shared<SDF>(*cache.Access().sdfParsed);
   // Read an SDF string, and store the result in sdfParsed.
   if (!readString(_sdf, _config, sdfParsed, errors))
   {
diff --git a/src/SDF.cc b/src/SDF.cc
@@ -219,6 +219,18 @@ SDF::SDF()
 {
 }
 
+/////////////////////////////////////////////////
+SDF::SDF(const SDF& other)
+{
+  this->dataPtr = std::make_unique<SDFPrivate>(*other.dataPtr);
+}
+
+/////////////////////////////////////////////////
+SDF& SDF::operator=(const SDF& other)
+{
+  this->dataPtr = std::make_unique<SDFPrivate>(*other.dataPtr);
+  return *this;
+}
 /////////////////////////////////////////////////
 SDF::~SDF()
 {
diff --git a/src/SDFImplPrivate.hh b/src/SDFImplPrivate.hh
@@ -37,6 +37,23 @@ namespace sdf
     {
     };
 
+    /// Copy constructor: Ensure Deep copy.
+    public: SDFPrivate(const SDFPrivate& other)
+    {
+      this->path = other.path;
+      this->originalVersion = other.originalVersion;
+      this->root = other.root->Clone();
+    }
+
+    /// Copy constructor: Ensure Deep Copy
+    public: SDFPrivate& operator=(const SDFPrivate& other)
+    {
+      this->path = other.path;
+      this->originalVersion = other.originalVersion;
+      this->root = other.root->Clone();
+      return *this;
+    }
+
     /// \brief Store the root element.
     /// \sa ElementPtr Root()
     /// \sa void Root(const ElementPtr _root)
diff --git a/src/SDF_TEST.cc b/src/SDF_TEST.cc
@@ -854,4 +854,29 @@ TEST(SDF, FindFileModelSDFCurrDir)
   ASSERT_EQ(std::remove(tempFile.c_str()), 0);
   std::filesystem::current_path(prevPath);
 }
+
+///////////////////////////////////////////////////
+// Test the copy constructor provides a deep copy
+TEST(SDF, CopyConstructor)
+{
+  // Set up a simple sdf model file
+  std::ostringstream stream;
+  stream << "<sdf version='1.3'>"
+         << "  <model name='test_model'>"
+         << "    <pose>0 1 2  0 0 0</pose>"
+         << "    <static>false</static>"
+         << "  </model>"
+         << "</sdf>";
+  sdf::SDF sdfParsed;
+  sdfParsed.SetFromString(stream.str());
+
+  sdf::SDF copy1sdfParsed(sdfParsed);
+  sdf::SDF copy2sdfParsed = sdfParsed;
+
+  sdfParsed.Root()->SetName("Test");
+  ASSERT_EQ(sdfParsed.Root()->GetName(), "Test");
+  // Since a deep copy occurs no changes should be reflected;
+  ASSERT_NE(copy1sdfParsed.Root()->GetName(), "Test");
+  ASSERT_NE(copy2sdfParsed.Root()->GetName(), "Test");
+}
 #endif  // _WIN32

Original file line number	Diff line number	Diff line change
`@@ -166,6 +166,8 @@ namespace sdf`
`166`	`166`	`class SDFORMAT_VISIBLE SDF`
`167`	`167`	`{`
`168`	`168`	`public: SDF();`
	`169`	`+ public: SDF(const SDF& other);`
	`170`	`+ public: SDF& operator=(const SDF& other);`
`169`	`171`	`/// \brief Destructor`
`170`	`172`	`public: ~SDF();`
`171`	`173`	`public: void PrintDescription();`
Original file line number	Diff line number	Diff line change
`@@ -219,6 +219,18 @@ SDF::SDF()`
`219`	`219`	`{`
`220`	`220`	`}`
`221`	`221`
	`222`	`+/////////////////////////////////////////////////`
	`223`	`+SDF::SDF(const SDF& other)`
	`224`	`+{`
	`225`	`+ this->dataPtr = std::make_unique<SDFPrivate>(*other.dataPtr);`
	`226`	`+}`
	`227`	`+`
	`228`	`+/////////////////////////////////////////////////`
	`229`	`+SDF& SDF::operator=(const SDF& other)`
	`230`	`+{`
	`231`	`+ this->dataPtr = std::make_unique<SDFPrivate>(*other.dataPtr);`
	`232`	`+ return *this;`
	`233`	`+}`
`222`	`234`	`/////////////////////////////////////////////////`
`223`	`235`	`SDF::~SDF()`
`224`	`236`	`{`