xmacro is a simple tool to define and parse XML macro. it's inspired by ros/xacro which is an XML macro language desiged for urdf, xmacro looks like simplified version of ros/xacro , but it's more simple, and also more easy to use.

• xmacro is independent of ROS, you could install it by pip .
• XML namespaces isn't used in xmacro , and there are some reserved words for xmacro : xmacro_include, xmacro_define_value, xmacro_define_block, xmacro_block.
• it provides python api so that we could parse xml file in ROS2 launch file.
• it provides xmacro4sdf : general xmacro with some specific function for sdf.

Installation

# install by pip
pip install xmacro
# install from source code
git clone https://github.com/gezp/xmacro.git
cd xmacro && sudo python3 setup.py install

examples

# some examples in folder test/
xmacro test_xmacro.xml.xmacro > test_xmacro.xml

• Value macro
• Block macro
• Math expressions
• Include
• Python API

Value macro are named values that can be inserted anywhere into the XML document except <xmacro_define_block> block.

xmacro definition

<!--definition of properties -->
<xmacro_define_value name="radius" value="4.3" />
<!--use of properties-->
<circle diameter="${2 * radius}" />

generated xml

<circle diameter="8.6" />

Define block macros with the macro tag <xmacro_define_block>, then specify the macro name and a list of parameters. The list of parameters should be whitespace separated.

The usage of block macros is to define <xmacro_block> which will be replaced with corresponding <xmacro_define_block> block.

xmacro definition

<!--definition of macro-->
	<xmacro_define_value name="mass" value="0.2" />
	<xmacro_define_block macro_name="box_inertia" params="m x y z">
        <mass>${m}</mass>
        <inertia>
            <ixx>${m*(y*y+z*z)/12}</ixx>
            <ixy>0</ixy>
            <ixz>0</ixz>
            <iyy>${m*(x*x+z*z)/12}</iyy>
            <iyz>0</iyz>
            <izz>${m*(x*x+z*z)/12}</izz>
        </inertia>
    </xmacro_define_block>
<!--use of macro-->
    <inertial>
         <pose>0 0 0.02 0 0 0</pose>
         <xmacro_block name="box_inertia" m="${mass}" x="0.3" y="0.1" z="0.2"/>
    </inertial>

generated xml

			<inertial>
				<pose>0 0 0.02 0 0 0</pose>
				<mass>0.2</mass>
				<inertia>
					<ixx>0.0008333333333333335</ixx>
					<ixy>0</ixy>
					<ixz>0</ixz>
					<iyy>0.002166666666666667</iyy>
					<iyz>0</iyz>
					<izz>0.002166666666666667</izz>
				</inertia>
			</inertial>

• only support simple parameters (string and number), and block parameters isn't supported.
• it's supported to use other xmacro_block in xmacro_define_block which is recursive definition.

it's not recommended to define macro recursively (only support <=5).

• within dollared-braces ${xxxx}, you can also write simple math expressions.
• refer to examples of **Value macro ** and **Block macro **
• it's implemented by calling eval() in python, so it's unsafe for some cases.

You can include other xmacro files by using the <xmacro_include> tag.

• it will include the xmcaro definition with tag <xmacro_define_value> and macros with tag <xmacro_define_block>.

<xmacro_include uri="file://simple_car/model.sdf.xmacro"/>

• The uri for file means to open the file directly.
  • it try to open the file with relative path simple_car/model.sdf.xmacro .
  • you can also try to open file with absolute path /simple_car/model.sdf.xmacro with uri file:///simple_car/model.sdf.xmacro.
• <xmacro_include> supports to include recursively.

you can use xmacro in python easily

from xmacro.xmacro import XMLMacro

xmacro=XMLMacro()
#case1 parse from file
xmacro.set_xml_file(inputfile)
xmacro.generate()
xmacro.to_file(outputfile)

#case2 parse from xml string
xmacro.set_xml_string(xml_str)
xmacro.generate()
xmacro.to_file(outputfile)

#case3 generate to string
xmacro.set_xml_file(inputfile)
xmacro.generate()
xmacro.to_string()

#case4 custom property
xmacro.set_xml_file(inputfile)
# use custom property dictionary to overwrite global property  
# defined by <xacro_define_property> (only in 'inputfile')
kv={"rplidar_a2_h":0.8}
xmacro.generate(kv)
xmacro.to_file(outputfile)

pre-defined common.sdf.xmacro

<!--macro defination:inertia-->
<xmacro_define_block name="inertia_cylinder" params="m r l">
<xmacro_define_block name="inertia_box" params="m x y z">
<xmacro_define_block name="inertia_sphere" params="m r">
<!--macro defination:geometry-->
<xmacro_define_block name="geometry_cylinder" params="r l">
<xmacro_define_block name="geometry_box" params="x y z">
<xmacro_define_block name="geometry_sphere" params="r">
<xmacro_define_block name="geometry_mesh" params="uri">
<!--macro defination:visual_collision_with_mesh-->
<xmacro_define_block name="visual_collision_with_mesh" params="prefix uri">

examples

# some examples in folder test/sdf
xmacro4sdf model.sdf.xmacro > model.sdf

maintainer : Zhenpeng Ge, [email protected]

xmacro is provided under MIT License.