Implementation:Google deepmind Mujoco XML Parser

Knowledge Sources	Google_deepmind_Mujoco
Domains	Physics Simulation, XML Parsing
Last Updated	2026-02-15 04:00 GMT

Overview

Implements the top-level XML parsing and saving interface for MuJoCo models, dispatching between MJCF and URDF formats.

Description

xml.cc serves as the main entry point for XML-based model loading and saving in MuJoCo. It uses tinyxml2 for XML document parsing, dispatches to mjXReader (MJCF native reader) or mjXURDF (URDF reader) based on document structure, and handles locale management to ensure consistent numeric formatting across different system locales. The file implements LocaleOverride classes for Windows, macOS, and Linux that temporarily switch to the "C" locale during XML operations to prevent comma-vs-period decimal separator issues.

Usage

Called when loading models via mj_loadXML, mj_parseXML, mj_saveXML, or any other XML-based model I/O operations.

Code Reference

Source Location

• Repository: Google_deepmind_Mujoco
• File: src/xml/xml.cc
• Lines: 1-395

Key Functions

// Top-level parsing using tinyxml2
// Locale-safe XML operations via LocaleOverride
// Dispatches to xml_native_reader.h (MJCF) or xml_urdf.h (URDF)

class LocaleOverride {
 public:
  LocaleOverride();   // switches to "C" locale
  ~LocaleOverride();  // restores original locale
};

Import

#include "xml/xml.h"
#include "xml/xml_native_reader.h"
#include "xml/xml_native_writer.h"
#include "xml/xml_urdf.h"
#include "tinyxml2.h"

I/O Contract

Inputs

Name	Type	Required	Description
filename	const char*	Yes	Path to XML file (MJCF or URDF format)
vfs	const mjVFS*	No	Virtual file system for resource lookups
error	char*	No	Buffer for error messages
error_sz	int	No	Size of error buffer

Outputs

Name	Type	Description
mjSpec*	mjSpec*	Parsed model specification from XML input
mjModel*	mjModel*	Compiled model (from mj_loadXML)
int	int	Return code for save operations (0 on success)

Related Pages

• Environment:Google_deepmind_Mujoco_C_Build_Environment