Using Advanced Resource Embedder

To embed files and generate Ada, C or Go source file, the Advanced Resource Embedder must identify the files, organize them and may be perform some transformation on these files before their integration. To control this process, it is possible to use some options passed to the are (1) tool but a better control is achieved by using an XML configuration file.

Defining resources

The XML file describes a list of resources that must be generated. It is introduced by the package root XML element and each resource is represented by a resource XML element. A resource is assigned a name and composed of several installation rules that describe how files are integrated and whether some transformations are made before their integration.

  <resource name='Help' format='string'>
    <install mode='xxx'>
  <resource name='Config' format='lines'>
    <install mode='xxx'>
  <resource name='Web' format='binary'>
    <install mode='xxx'>
    <install mode='yyy'>

The resource content can be available in several formats by the code generator. This format is controlled by the format attribute. The following data formats are supported:

  • binary format provides the file content as a binary data.
  • string format provides the file content as string.
  • lines format splits the content in several lines and according to a set of customisable rules.

To help you in the control of the generated code, the resource description can also define specific attributes that allow you to tune the code generator. The following XML definition:

  <resource name='Help'
    <install mode='copy'>
      <fileset dir="help">
        <include name="**/*.txt"/>

creates a resource named Help and composed of text files located in the help directory and with the .txt file extension. The code generator will use the name man_content for the data type that represents the file description and it will use man_get_help_content for the generated function name.

Controlling the lines format

The lines format tells the code generator to represent the content as an array of separate lines. For this integration, some control is available to indicate how the content must be split and optionaly apply some filter on the input content. These controls are made within the XML description by using the line-separator and line-filter description: The line-separator indicates the characters that represent a line separation. There can be several line-separator definition. The line-filter defines a regular expression that when matched must be replaced by an empty string or a specified content. The line-filter are applied in the order of the XML definition.

The example below is intended to integrate an SQL scripts with:

  • a separate line for each SQL statement,
  • remove spurious empty lines and SQL comments.

The SQL statements are separated by ; (semi-colon) and the line-separator indicates to split lines on that character. By splitting on the ;, we allow to have an SQL statement on multiple lines.

  <resource name='Scripts'
            format='lines' keep-empty-lines="no"
            type='access constant String'>

    <!-- Remove new lines -->

    <!-- Remove C comments -->

    <!-- Remove contiguous spaces after C comments removal -->
    <line-filter replace=' '>[ \t][ \t]+</line-filter>

    <install mode='copy' strip-extension='yes'>
      <fileset dir="sql">
        <include name="**/*.sql"/>

Then the first line-filter will remove the \r and \n characters.

The regular expression /\*[^/]*\*/ matches a C style comment and remove it.

The last line-filter replaces multiple tabs and spaces by a single occurence.

By default an empty line is discarded. This behavior can be changed by using the keep-empty-lines attribute and setting the value to true.

Selecting files

An important step in the configuration of the Advanced Resource Embedder is the selection of files that will be embedded. The mechanism to select files is heavily inspired by the ant (1) Java builder with the notion of filesets and patterns.

A fileset describes a collection of files stored in a directory and it uses a set of inclusion and exclusion patterns to select files of that directory. A fileset is described by the fileset XML element and it can contain several include and exclude XML element. Each include element describes a pattern that the file must match to be taken into account. Sometimes a file can be matched but you want to exclude it and you will use the exclude XML element to reject that file.

A pattern a either a fixed relative path or it may contain wildcards. A single wildcard pattern applies only to a single directory and the special notation **/ indicates to match any child directory.

The following definition:

  <include name="*.html"/>
  <include name="*.css"/>
  <include name="*.js"/>
  <exclude name="test.js"/>

will select files from the directories passed to the are tool and it takes into account only files with .html, .css and .js extension. Child directories are excluded as well as the test.js file if it exists.

A fileset can indicate a directory name by using the dir attribute. In that case, the file selection will start from the directory with the given name.

<fileset dir='web'>
  <include name="**/*.html"/>
  <include name="**/*.css"/>
  <include name="**/*.js"/>
  <exclude name="preview/**"/>

That definition scans the web directory for each argument passed to the are tool and selects recursively all .html, .css and .js files. If the web directory contains a preview directory, that directory and any file it contains will be excluded.

You may include and combine several fileset XML element to describe complex file selection.

Integration modes

The Advanced Resource Embedder provides several modes for the integration of a file. After files are matched, a decision must be made on the files to integrate them in the output. Sometimes it happens that several source files will correspond to a single output. For this integration, it is possible to make some specific transformations.

The installation rule is described by the install XML element. That rule in fact contains the fileset that indicates the files that must be taken into account by the installation rule.

<install mode='copy'>
    <include name='**/*.txt'/>

The installation modes are described more into details in the Rules chapter.

Man page


are - Resource embedder to include files in Ada, C/C++, Go binaries


are [ -v ] [-vv] [-V] [--tmp directory ] [-k] [--keep] [-o directory ] [-l lang ] [--rule path ] [--resource name ] [--fileset pattern ] [--ignore-case] [--list-access] [--var-access] [--var-prefix prefix ] [--no-type-declaration] [--type-name name ] [--function-name name ] [--member-content name ] [--member-length name ] [--member-modtime name ] [--member-format name ] [--preelaborate] [--content-only] directory...


are is a tool to generate C, Ada or Go source allowing to embed files in a binary program by compiling and linking with the compiled generated sources.

The process to use are is simple and composed of three steps:

  • First, you describe the resources that you want to embed. The description is either made on command line arguments or by writing an XML file. The XML description gives more flexibility as it allows to define a transformation rule that must be executed on the original file before being embedded. This allows to minify a Javascript or CSS file, compress some files and even encrypt a file before its integration.

  • You run the are command with the your target language and rule description and you give the tool a list of directories that must be scanned to identify the files that must be collected. The are tool scan the directories according to the patterns that you have given either on the command line or in the XML rule description. After identifying the files, the tool applies the rules and execute the transformations. The are tool then invokes the target language generator that writes one or several files depending on the list of resources.

  • Once the files are generated, you use them in your program and add them in your build process as they are now part of your sources. After building your program, it now embeds the resource files that were collected and optionally transformed.

The identification of files is made by using fileset patterns similar to the ant(1) tool. The patterns are applied to the directories that are passed to the are tool. Files that match the pattern are selected and taken into account. The pattern can be an exact relative path definition or it may contain wildcards. Below are some examples:

.txt This pattern matches all files with a .txt extension in the directories passed to the command. Only the root directories are taken into account (the .txt* files in sub-directories are ignored).

/.txt The / pattern indicates that the pattern is applied on directories recursively. The files must then match the .txt pattern to be taken into account. Therefore, the /.txt pattern will match all .txt* files in any directory.

config/.conf This pattern will match the .conf files in the config* directory.

web/index.html This pattern matches a fixed path.


The following options are recognized by are:

-V Prints the are version.

-v Enable the verbose mode.

-vv Enable debugging output.

--tmp directory Use the directory to build the resource files. The default directory is are-generator and it is created in the current working directory. This option allows to choose another path.

--keep Keep the directory used to prepare the resource files. By default the are-generator directory (which can be overriden by the --tmp option) is removed when the code generation is finished. By keeping the directory, you can have a look at the files and their transformations.

--output directory Set the output directory path where generators writes the code.

--lang language Select the target generator language. The supported languages are Ada, C, and Go. The default language is Ada.

--rule path Read the XML file that describes the resources to generate. The use of a XML resource file allows to use the advance features of the tool such as doing some transformations on the input files. The XML resource file can describe several resources and provides mechanisms to control the generation for each of them.

--resource name Define the name of the resource collection. This option is used to create a resource with the given name.

--fileset pattern Define the pattern to match files for the resource collection. After the --resource option, this indicates the pattern to match the files for that resource.

--name-access Generate support to query content with a name. The code generator will declare and genrate a function which given a name returns the embedded content if that name is known.

--list-access Generate support to list the content names. Most code generator will declare a variable that represents a sorted list of names which represents the resource. It is possible to use a dichotomic search on that name array.

--var-access Declare a variable to give access to each content. When this option is given, the code generator will emit a global variable declaration with the name of the file. By using the global variable, the program can access the resource directly.

--var-prefix prefix Defines the prefix to be used for the variable declarations that give access access to each content. This option implies the --var-access option.

--no-type-declaration Do not declare any type in the package specification. It is assumed that the types used by the generated code is declared somewhere else and is visible during the compilation.

--type-name name Define the name of the type used to hold the information. This is the name of the C, Ada or Go type that is generated. It must be a valid name of the target language.

--member-content name Define the name data structure member holding the content.

--member-length name Define the name data structure member holding the length.

--member-modtime name Define the name data structure member holding the modification time.

--member-format name Define the name data structure member holding the content format

--preelaborate This option is recognized by the Ada generator and it tells it to emit a pragma Preelaborate in the generated specification file.

--content-only This option is specific to the Ada generator and instructs the generator to only give access to the content.


The rule descritions are best expressed by using an XML file. The XML file can describe several resources and for each of them it defines the files that must be included with their optional transformation. The XML file must have a package root element.

A resource is described by the resource XML element with a mandatory name attribute that indicates the name of the resource. It then contains an install XML element which describes the installation rule with the patterns that identify the files.

  <resource name='help' format='string'>
   <install mode='copy'>
     <fileset dir='help'>
      <include name='**/*.txt'/>

A resource can be represented as an array of strings by using the lines format. In that case, a line-separator XML element indicates the character on which lines are split. The keep-empty-lines attribute controls whether an empty line is kept or must be discarded. The default will discard empty lines. With the lines format, the final content will be represented as an array of strings.

  <resource name='help' format='lines' keep-empty-lines='true'>
   <install mode='copy'>
     <fileset dir='help'>
      <include name='**/*.txt'/>


The are tool provides several installation modes:

copy Copy the file.

copy-first Copy the first file.

exec Execute a command with the file.

copy-exec The file is copied and a command is then executed with the target path for some transformations.

concat The files that match the pattern are concatenated.

bundle This mode concern Java like property files and allows to do some specific merge in the files.

merge This mode concern Java like property files and allows to do some specific merge in the files.


ant(1), gprbuild(1), gzip(1), closure(1), yui-compressor(1)


Written by Stephane Carrez.