Table of Contents



Introduction Building, Installing, and Packaging Mini-XML Getting Started with Mini-XML More Mini-XML Programming Techniques Using the mxmldoc Utility Mini-XML License

Release Notes Library Reference XML Schema

0Introduction

This programmers manual describes Mini-XML version 2.7, a small XML parsing library that you can use to read and write XML data files in your C and C++ applications.

Mini-XML was initially developed for the Gutenprint project to replace the rather large and unwieldy libxml2 library with something substantially smaller and easier-to-use. It all began one morning in June of 2003 when Robert posted the following sentence to the developer's list:

It's bad enough that we require libxml2, but rolling our own XML parser is a bit more than we can handle.

I then replied with:

Given the limited scope of what you use in XML, it should be trivial to code a mini-XML API in a few hundred lines of code.

I took my own challenge and coded furiously for two days to produced the initial public release of Mini-XML, total lines of code: 696. Robert promptly integrated Mini-XML into Gutenprint and removed libxml2.

Thanks to lots of feedback and support from various developers, Mini-XML has evolved since then to provide a more complete XML implementation and now stands at a whopping 3,747 lines of code, compared to 103,893 lines of code for libxml2 version 2.6.9.

Aside from Gutenprint, Mini-XML is used for the following projects/software applications:

Please email me (mxml @ easysw . com) if you would like your project added or removed from this list, or if you have any comments/quotes you would like me to publish about your experiences with Mini-XML.

Organization of This Document

This manual is organized into the following chapters and appendices:

Notation Conventions

Various font and syntax conventions are used in this guide. Examples and their meanings and uses are explained below:

mxmldoc
mxmldoc(1)
The names of commands; the first mention of a command or function in a chapter is followed by a manual page section number.

/var
/etc/hosts
File and directory names.

Request ID is Printer-123
Screen output.

lp -d printer filename ENTER
Literal user input; special keys like ENTER are in ALL CAPS.

12.3
Numbers in the text are written using the period (.) to indicate the decimal point.

Abbreviations

The following abbreviations are used throughout this manual:

Gb
Gigabytes, or 1073741824 bytes

kb
Kilobytes, or 1024 bytes

Mb
Megabytes, or 1048576 bytes

UTF-8, UTF-16
Unicode Transformation Format, 8-bit or 16-bit

W3C
World Wide Web Consortium

XML
Extensible Markup Language

Other References

The Unicode Standard, Version 4.0, Addison-Wesley, ISBN 0-321-18578-1
The definition of the Unicode character set which is used for XML.

Extensible Markup Language (XML) 1.0 (Third Edition)
The XML specification from the World Wide Web Consortium (W3C)

Legal Stuff

The Mini-XML library is copyright 2003-2011 by Michael Sweet. License terms are described in Appendix A - Mini-XML License .


1Building, Installing, and Packaging Mini-XML

This chapter describes how to build, install, and package Mini-XML on your system from the source archive. You will need an ANSI/ISO-C compatible compiler to build Mini-XML - GCC works, as do most vendors' C compilers. If you are building Mini-XML on Windows, we recommend using the Visual C++ environment with the supplied solution file. For other operating systems, you'll need a POSIX-compatible shell and make program in addition to the C compiler.

Compiling Mini-XML

Mini-XML comes with both an autoconf-based configure script and a Visual C++ solution that can be used to compile the library and associated tools.

Compiling with Visual C++

Open the mxml.sln solution in the vcnet folder. Choose the desired build configuration, "Debug" (the default) or "Release", and then choose Build Solution from the Build menu.

Compiling with Command-Line Tools

Type the following command to configure the Mini-XML source code for your system:

    ./configure ENTER

The default install prefix is /usr/local, which can be overridden using the --prefix option:

    ./configure --prefix=/foo ENTER

Other configure options can be found using the --help option:

    ./configure --help ENTER

Once you have configured the software, use the make(1) program to do the build and run the test program to verify that things are working, as follows:

    make ENTER

Installing Mini-XML

If you are using Visual C++, copy the mxml.lib and and mxml.h files to the Visual C++ lib and include directories, respectively.

Otherwise, use the make command with the install target to install Mini-XML in the configured directories:

    make install ENTER

Creating Mini-XML Packages

Mini-XML includes two files that can be used to create binary packages. The first file is mxml.spec which is used by the rpmbuild(8) software to create Red Hat Package Manager ("RPM") packages which are commonly used on Linux. Since rpmbuild wants to compile the software on its own, you can provide it with the Mini-XML tar file to build the package:

    rpmbuild -ta mxml-version.tar.gz ENTER

The second file is mxml.list which is used by the epm(1) program to create software packages in a variety of formats. The epm program is available from the following URL:

    http://www.easysw.com/epm/

Use the make command with the epm target to create portable and native packages for your system:

    make epm ENTER

The packages are stored in a subdirectory named dist for your convenience. The portable packages utilize scripts and tar files to install the software on the target system. After extracting the package archive, use the mxml.install script to install the software.

The native packages will be in the local OS's native format: RPM for Red Hat Linux, DPKG for Debian Linux, PKG for Solaris, and so forth. Use the corresponding commands to install the native packages.


2Getting Started with Mini-XML

This chapter describes how to write programs that use Mini-XML to access data in an XML file. Mini-XML provides the following functionality:

Mini-XML doesn't do validation or other types of processing on the data based upon schema files or other sources of definition information, nor does it support character entities other than those required by the XML specification.

The Basics

Mini-XML provides a single header file which you include:

    #include <mxml.h>

The Mini-XML library is included with your program using the -lmxml option:

    gcc -o myprogram myprogram.c -lmxml ENTER

If you have the pkg-config(1) software installed, you can use it to determine the proper compiler and linker options for your installation:

    pkg-config --cflags mxml ENTER
    pkg-config --libs mxml ENTER

Nodes

Every piece of information in an XML file (elements, text, numbers) is stored in memory in "nodes". Nodes are defined by the mxml_node_t structure. The type member defines the node type (element, integer, opaque, real, or text) which determines which value you want to look at in the value union.

Table 2-1: Mini-XML Node Value Members
ValueTypeNode member
Customvoid * node->value.custom.data
Elementchar * node->value.element.name
Integerintnode->value.integer
Opaque (string)char * node->value.opaque
Realdoublenode->value.real
Textchar *node->value.text.string

Each node also has a user_data member which allows you to associate application-specific data with each node as needed.

New nodes are created using the mxmlNewElement, mxmlNewInteger , mxmlNewOpaque, mxmlNewReal, mxmlNewText , mxmlNewTextf, and mxmlNewXML functions. Only elements can have child nodes, and the top node must be an element, usually the <?xml version="1.0" encoding="utf-8"?> node created by mxmlNewXML() .

Nodes have pointers to the node above (parent), below ( child), left (prev), and right (next) of the current node. If you have an XML file like the following:

    <?xml version="1.0" encoding="utf-8"?>
    <data>
        <node>val1</node>
        <node>val2</node>
        <node>val3</node>
        <group>
            <node>val4</node>
            <node>val5</node>
            <node>val6</node>
        </group>
        <node>val7</node>
        <node>val8</node>
    </data>

the node tree for the file would look like the following in memory:

    ?xml version="1.0" encoding="utf-8"?
      |
    data
      |
    node - node - node - group - node - node
      |      |      |      |       |      |
    val1   val2   val3     |     val7   val8
                           |
                         node - node - node
                           |      |      |
                         val4   val5   val6

where "-" is a pointer to the next node and "|" is a pointer to the first child node.

Once you are done with the XML data, use the mxmlDelete function to recursively free the memory that is used for a particular node or the entire tree:

    mxmlDelete(tree);

Creating XML Documents

You can create and update XML documents in memory using the various mxmlNew functions. The following code will create the XML document described in the previous section:

    mxml_node_t *xml;    /* <?xml ... ?> */
    mxml_node_t *data;   /* <data> */
    mxml_node_t *node;   /* <node> */
    mxml_node_t *group;  /* <group> */

    xml = mxmlNewXML("1.0");

    data = mxmlNewElement(xml, "data");

        node = mxmlNewElement(data, "node");
        mxmlNewText(node, 0, "val1");
        node = mxmlNewElement(data, "node");
        mxmlNewText(node, 0, "val2");
        node = mxmlNewElement(data, "node");
        mxmlNewText(node, 0, "val3");

        group = mxmlNewElement(data, "group");

            node = mxmlNewElement(group, "node");
            mxmlNewText(node, 0, "val4");
            node = mxmlNewElement(group, "node");
            mxmlNewText(node, 0, "val5");
            node = mxmlNewElement(group, "node");
            mxmlNewText(node, 0, "val6");

        node = mxmlNewElement(data, "node");
        mxmlNewText(node, 0, "val7");
        node = mxmlNewElement(data, "node");
        mxmlNewText(node, 0, "val8");

We start by creating the <?xml version="1.0" encoding="utf-8"?> node common to all XML files using the mxmlNewXML function:

    xml = mxmlNewXML("1.0");

We then create the <data> node used for this document using the mxmlNewElement function. The first argument specifies the parent node (xml) while the second specifies the element name (data):

    data = mxmlNewElement(xml, "data");

Each <node>...</node> in the file is created using the mxmlNewElement and mxmlNewText functions. The first argument of mxmlNewText specifies the parent node (node). The second argument specifies whether whitespace appears before the text - 0 or false in this case. The last argument specifies the actual text to add:

    node = mxmlNewElement(data, "node");
    mxmlNewText(node, 0, "val1");

The resulting in-memory XML document can then be saved or processed just like one loaded from disk or a string.

Loading XML

You load an XML file using the mxmlLoadFile function:

    FILE *fp;
    mxml_node_t *tree;

    fp = fopen("filename.xml", "r");
    tree = mxmlLoadFile(NULL, fp,
                        MXML_TEXT_CALLBACK);
    fclose(fp);

The first argument specifies an existing XML parent node, if any. Normally you will pass NULL for this argument unless you are combining multiple XML sources. The XML file must contain a complete XML document including the ?xml element if the parent node is NULL.

The second argument specifies the stdio file to read from, as opened by fopen() or popen(). You can also use stdin if you are implementing an XML filter program.

The third argument specifies a callback function which returns the value type of the immediate children for a new element node: MXML_CUSTOM, MXML_IGNORE, MXML_INTEGER, MXML_OPAQUE, MXML_REAL, or MXML_TEXT. Load callbacks are described in detail in Chapter 3. The example code uses the MXML_TEXT_CALLBACK constant which specifies that all data nodes in the document contain whitespace-separated text values. Other standard callbacks include MXML_IGNORE_CALLBACK, MXML_INTEGER_CALLBACK, MXML_OPAQUE_CALLBACK, and MXML_REAL_CALLBACK.

The mxmlLoadString function loads XML node trees from a string:

    char buffer[8192];
    mxml_node_t *tree;

    ...
    tree = mxmlLoadString(NULL, buffer,
                          MXML_TEXT_CALLBACK);

The first and third arguments are the same as used for mxmlLoadFile(). The second argument specifies the string or character buffer to load and must be a complete XML document including the ?xml element if the parent node is NULL.

Saving XML

You save an XML file using the mxmlSaveFile function:

    FILE *fp;
    mxml_node_t *tree;

    fp = fopen("filename.xml", "w");
    mxmlSaveFile(tree, fp, MXML_NO_CALLBACK);
    fclose(fp);

The first argument is the XML node tree to save. It should normally be a pointer to the top-level ?xml node in your XML document.

The second argument is the stdio file to write to, as opened by fopen() or popen(). You can also use stdout if you are implementing an XML filter program.

The third argument is the whitespace callback to use when saving the file. Whitespace callbacks are covered in detail in Chapter 3. The previous example code uses the MXML_NO_CALLBACK constant to specify that no special whitespace handling is required.

The mxmlSaveAllocString, and mxmlSaveString functions save XML node trees to strings:

    char buffer[8192];
    char *ptr;
    mxml_node_t *tree;

    ...
    mxmlSaveString(tree, buffer, sizeof(buffer),
                   MXML_NO_CALLBACK);

    ...
    ptr = mxmlSaveAllocString(tree, MXML_NO_CALLBACK);

The first and last arguments are the same as used for mxmlSaveFile(). The mxmlSaveString function takes pointer and size arguments for saving the XML document to a fixed-size buffer, while mxmlSaveAllocString() returns a string buffer that was allocated using malloc().

Controlling Line Wrapping

When saving XML documents, Mini-XML normally wraps output lines at column 75 so that the text is readable in terminal windows. The mxmlSetWrapMargin function overrides the default wrap margin:

    /* Set the margin to 132 columns */
    mxmlSetWrapMargin(132);

    /* Disable wrapping */
    mxmlSetWrapMargin(0);

Finding and Iterating Nodes

The mxmlWalkPrev and mxmlWalkNextfunctions can be used to iterate through the XML node tree:

    mxml_node_t *node;
    
    node = mxmlWalkPrev(current, tree,
                        MXML_DESCEND);

    node = mxmlWalkNext(current, tree,
                        MXML_DESCEND);

In addition, you can find a named element/node using the mxmlFindElement function:

    mxml_node_t *node;
    
    node = mxmlFindElement(tree, tree, "name",
                           "attr", "value",
                           MXML_DESCEND);

The name, attr, and value arguments can be passed as NULL to act as wildcards, e.g.:

    /* Find the first "a" element */
    node = mxmlFindElement(tree, tree, "a",
                           NULL, NULL,
                           MXML_DESCEND);
    /* Find the first "a" element with "href"
       attribute */
    node = mxmlFindElement(tree, tree, "a",
                           "href", NULL,
                           MXML_DESCEND);
    /* Find the first "a" element with "href"
       to a URL */
    node = mxmlFindElement(tree, tree, "a",
                           "href",
                           "http://www.easysw.com/",
                           MXML_DESCEND);
    /* Find the first element with a "src"
       attribute */
    node = mxmlFindElement(tree, tree, NULL,
                           "src", NULL,
                           MXML_DESCEND);
    /* Find the first element with a "src"
       = "foo.jpg" */
    node = mxmlFindElement(tree, tree, NULL,
                           "src", "foo.jpg",
                           MXML_DESCEND);

You can also iterate with the same function:

    mxml_node_t *node;

    for (node = mxmlFindElement(tree, tree,
                                "name",
                                NULL, NULL,
                                MXML_DESCEND);
         node != NULL;
         node = mxmlFindElement(node, tree,
                                "name",
                                NULL, NULL,
                                MXML_DESCEND))
    {
      ... do something ...
    }

The MXML_DESCEND argument can actually be one of three constants:

Finding Value Nodes

You can find the value of a specific node in the tree using the mxmlFindValue, for example:

    mxml_node_t *value = mxmlFindValue(tree, "path/to/*/foo/bar");

The second argument is a "path" to the parent node. Each component of the path is separated by a slash (/) and represents a named element in the document tree or a wildcard (*) path representing 0 or more intervening nodes.


3More Mini-XML Programming Techniques

This chapter shows additional ways to use the Mini-XML library in your programs.

Load Callbacks

Chapter 2 introduced the mxmlLoadFile() and mxmlLoadString() functions. The last argument to these functions is a callback function which is used to determine the value type of each data node in an XML document.

Mini-XML defines several standard callbacks for simple XML data files:

You can provide your own callback functions for more complex XML documents. Your callback function will receive a pointer to the current element node and must return the value type of the immediate children for that element node: MXML_INTEGER, MXML_OPAQUE, MXML_REAL, or MXML_TEXT. The function is called after the element and its attributes have been read, so you can look at the element name, attributes, and attribute values to determine the proper value type to return.

The following callback function looks for an attribute named "type" or the element name to determine the value type for its child nodes:

    mxml_type_t
    type_cb(mxml_node_t *node)
    {
      const char *type;

     /*
      * You can lookup attributes and/or use the
      * element name, hierarchy, etc...
      */

      type = mxmlElementGetAttr(node, "type");
      if (type == NULL)
	type = node->value.element.name;

      if (!strcmp(type, "integer"))
	return (MXML_INTEGER);
      else if (!strcmp(type, "opaque"))
	return (MXML_OPAQUE);
      else if (!strcmp(type, "real"))
	return (MXML_REAL);
      else
	return (MXML_TEXT);
    }

To use this callback function, simply use the name when you call any of the load functions:

    FILE *fp;
    mxml_node_t *tree;

    fp = fopen("filename.xml", "r");
    tree = mxmlLoadFile(NULL, fp, type_cb);
    fclose(fp);

Save Callbacks

Chapter 2 also introduced the mxmlSaveFile(), mxmlSaveString(), and mxmlSaveAllocString() functions. The last argument to these functions is a callback function which is used to automatically insert whitespace in an XML document.

Your callback function will be called up to four times for each element node with a pointer to the node and a "where" value of MXML_WS_BEFORE_OPEN, MXML_WS_AFTER_OPEN, MXML_WS_BEFORE_CLOSE, or MXML_WS_AFTER_CLOSE. The callback function should return NULL if no whitespace should be added and the string to insert (spaces, tabs, carriage returns, and newlines) otherwise.

The following whitespace callback can be used to add whitespace to XHTML output to make it more readable in a standard text editor:

    const char *
    whitespace_cb(mxml_node_t *node,
                  int where)
    {
      const char *name;

     /*
      * We can conditionally break to a new line
      * before or after any element. These are
      * just common HTML elements...
      */

      name = node->value.element.name;

      if (!strcmp(name, "html") ||
          !strcmp(name, "head") ||
          !strcmp(name, "body") ||
	  !strcmp(name, "pre") ||
          !strcmp(name, "p") ||
	  !strcmp(name, "h1") ||
          !strcmp(name, "h2") ||
          !strcmp(name, "h3") ||
	  !strcmp(name, "h4") ||
          !strcmp(name, "h5") ||
          !strcmp(name, "h6"))
      {
       /*
	* Newlines before open and after
        * close...
	*/

	if (where == MXML_WS_BEFORE_OPEN ||
            where == MXML_WS_AFTER_CLOSE)
	  return ("\n");
      }
      else if (!strcmp(name, "dl") ||
               !strcmp(name, "ol") ||
               !strcmp(name, "ul"))
      {
       /*
	* Put a newline before and after list
        * elements...
	*/

	return ("\n");
      }
      else if (!strcmp(name, "dd") ||
               !strcmp(name, "dt") ||
               !strcmp(name, "li"))
      {
       /*
	* Put a tab before <li>'s, * <dd>'s,
        * and <dt>'s, and a newline after them...
	*/

	if (where == MXML_WS_BEFORE_OPEN)
	  return ("\t");
	else if (where == MXML_WS_AFTER_CLOSE)
	  return ("\n");
      }

     /*
      * Return NULL for no added whitespace...
      */

      return (NULL);
    }

To use this callback function, simply use the name when you call any of the save functions:

    FILE *fp;
    mxml_node_t *tree;

    fp = fopen("filename.xml", "w");
    mxmlSaveFile(tree, fp, whitespace_cb);
    fclose(fp);

Custom Data Types

Mini-XML supports custom data types via global load and save callbacks. Only a single set of callbacks can be active at any time, however your callbacks can store additional information in order to support multiple custom data types as needed. The MXML_CUSTOM node type identifies custom data nodes.

The load callback receives a pointer to the current data node and a string of opaque character data from the XML source with character entities converted to the corresponding UTF-8 characters. For example, if we wanted to support a custom date/time type whose value is encoded as "yyyy-mm-ddThh:mm:ssZ" (ISO format), the load callback would look like the following:

    typedef struct
    {
      unsigned      year,    /* Year */
                    month,   /* Month */
                    day,     /* Day */
                    hour,    /* Hour */
                    minute,  /* Minute */
                    second;  /* Second */
      time_t        unix;    /* UNIX time */
    } iso_date_time_t;

    int
    load_custom(mxml_node_t *node,
                const char *data)
    {
      iso_date_time_t *dt;
      struct tm tmdata;

     /*
      * Allocate data structure...
      */

      dt = calloc(1, sizeof(iso_date_time_t));

     /*
      * Try reading 6 unsigned integers from the
      * data string...
      */

      if (sscanf(data, "%u-%u-%uT%u:%u:%uZ",
                 &(dt->year), &(dt->month),
                 &(dt->day), &(dt->hour),
                 &(dt->minute),
                 &(dt->second)) != 6)
      {
       /*
        * Unable to read numbers, free the data
        * structure and return an error...
        */

        free(dt);

        return (-1);
      }

     /*
      * Range check values...
      */

      if (dt->month <1 || dt->month > 12 ||
          dt->day  <1 || dt->day > 31 ||
          dt->hour  <0 || dt->hour > 23 ||
          dt->minute  <0 || dt->minute > 59 ||
          dt->second  <0 || dt->second > 59)
      {
       /*
        * Date information is out of range...
        */

        free(dt);

        return (-1);
      }

     /*
      * Convert ISO time to UNIX time in
      * seconds...
      */

      tmdata.tm_year = dt->year - 1900;
      tmdata.tm_mon  = dt->month - 1;
      tmdata.tm_day  = dt->day;
      tmdata.tm_hour = dt->hour;
      tmdata.tm_min  = dt->minute;
      tmdata.tm_sec  = dt->second;

      dt->unix = gmtime(&tmdata);

     /*
      * Assign custom node data and destroy
      * function pointers...
      */

      node->value.custom.data    = dt;
      node->value.custom.destroy = free;

     /*
      * Return with no errors...
      */

      return (0);
    }

The function itself can return 0 on success or -1 if it is unable to decode the custom data or the data contains an error. Custom data nodes contain a void pointer to the allocated custom data for the node and a pointer to a destructor function which will free the custom data when the node is deleted.

The save callback receives the node pointer and returns an allocated string containing the custom data value. The following save callback could be used for our ISO date/time type:

    char *
    save_custom(mxml_node_t *node)
    {
      char data[255];
      iso_date_time_t *dt;


      dt = (iso_date_time_t *)node->custom.data;

      snprintf(data, sizeof(data),
               "%04u-%02u-%02uT%02u:%02u:%02uZ",
               dt->year, dt->month, dt->day,
               dt->hour, dt->minute, dt->second);

      return (strdup(data));
    }

You register the callback functions using the mxmlSetCustomHandlers() function:

    mxmlSetCustomHandlers(load_custom,
                          save_custom);

Changing Node Values

All of the examples so far have concentrated on creating and loading new XML data nodes. Many applications, however, need to manipulate or change the nodes during their operation, so Mini-XML provides functions to change node values safely and without leaking memory.

Existing nodes can be changed using the mxmlSetElement(), mxmlSetInteger(), mxmlSetOpaque() , mxmlSetReal(), mxmlSetText(), and mxmlSetTextf() functions. For example, use the following function call to change a text node to contain the text "new" with leading whitespace:

    mxml_node_t *node;

    mxmlSetText(node, 1, "new");

Formatted Text

The mxmlNewTextf() and mxmlSetTextf() functions create and change text nodes, respectively, using printf-style format strings and arguments. For example, use the following function call to create a new text node containing a constructed filename:

    mxml_node_t *node;

    node = mxmlNewTextf(node, 1, "%s/%s",
                        path, filename);

Indexing

Mini-XML provides functions for managing indices of nodes. The current implementation provides the same functionality as mxmlFindElement(). The advantage of using an index is that searching and enumeration of elements is significantly faster. The only disadvantage is that each index is a static snapshot of the XML document, so indices are not well suited to XML data that is updated more often than it is searched. The overhead of creating an index is approximately equal to walking the XML document tree. Nodes in the index are sorted by element name and attribute value.

Indices are stored in mxml_index_t structures. The mxmlIndexNew() function creates a new index:

    mxml_node_t *tree;
    mxml_index_t *ind;

    ind = mxmlIndexNew(tree, "element",
                       "attribute");

The first argument is the XML node tree to index. Normally this will be a pointer to the ?xml element.

The second argument contains the element to index; passing NULL indexes all element nodes alphabetically.

The third argument contains the attribute to index; passing NULL causes only the element name to be indexed.

Once the index is created, the mxmlIndexEnum(), mxmlIndexFind() , and mxmlIndexReset() functions are used to access the nodes in the index. The mxmlIndexReset() function resets the "current" node pointer in the index, allowing you to do new searches and enumerations on the same index. Typically you will call this function prior to your calls to mxmlIndexEnum() and mxmlIndexFind().

The mxmlIndexEnum() function enumerates each of the nodes in the index and can be used in a loop as follows:

    mxml_node_t *node;

    mxmlIndexReset(ind);

    while ((node = mxmlIndexEnum(ind)) != NULL)
    {
      // do something with node
    }

The mxmlIndexFind() function locates the next occurrence of the named element and attribute value in the index. It can be used to find all matching elements in an index, as follows:

    mxml_node_t *node;

    mxmlIndexReset(ind);

    while ((node = mxmlIndexFind(ind, "element",
                                 "attr-value"))
                != NULL)
    {
      // do something with node
    }

The second and third arguments represent the element name and attribute value, respectively. A NULL pointer is used to return all elements or attributes in the index. Passing NULL for both the element name and attribute value is equivalent to calling mxmlIndexEnum.

When you are done using the index, delete it using the mxmlIndexDelete() function:

    mxmlIndexDelete(ind);

SAX (Stream) Loading of Documents

Mini-XML supports an implementation of the Simple API for XML (SAX) which allows you to load and process an XML document as a stream of nodes. Aside from allowing you to process XML documents of any size, the Mini-XML implementation also allows you to retain portions of the document in memory for later processing.

The mxmlSAXLoadFd, mxmlSAXLoadFile, and mxmlSAXLoadString functions provide the SAX loading APIs. Each function works like the corresponding mxmlLoad function but uses a callback to process each node as it is read.

The callback function receives the node, an event code, and a user data pointer you supply:

    void
    sax_cb(mxml_node_t *node,
           mxml_sax_event_t event,
           void *data)
    {
      ... do something ...
    }

The event will be one of the following:

Elements are released after the close element is processed. All other nodes are released after they are processed. The SAX callback can retain the node using the mxmlRetain function. For example, the following SAX callback will retain all nodes, effectively simulating a normal in-memory load:

    void
    sax_cb(mxml_node_t *node,
           mxml_sax_event_t event,
           void *data)
    {
      if (event != MXML_SAX_ELEMENT_CLOSE)
        mxmlRetain(node);
    }

More typically the SAX callback will only retain a small portion of the document that is needed for post-processing. For example, the following SAX callback will retain the title and headings in an XHTML file. It also retains the (parent) elements like <html>, <head>, and <body>, and processing directives like <?xml ... ?> and <!DOCTYPE ... >:

    void
    sax_cb(mxml_node_t *node,
           mxml_sax_event_t event,
           void *data)
    {
      if (event == MXML_SAX_ELEMENT_OPEN)
      {
       /*
        * Retain headings and titles...
        */

        char *name = node->value.element.name;

        if (!strcmp(name, "html") ||
            !strcmp(name, "head") ||
            !strcmp(name, "title") ||
            !strcmp(name, "body") ||
            !strcmp(name, "h1") ||
            !strcmp(name, "h2") ||
            !strcmp(name, "h3") ||
            !strcmp(name, "h4") ||
            !strcmp(name, "h5") ||
            !strcmp(name, "h6"))
          mxmlRetain(node);
      }
      else if (event == MXML_SAX_DIRECTIVE)
        mxmlRetain(node);
      else if (event == MXML_SAX_DATA &&
               node->parent->ref_count > 1)
      {
       /*
        * If the parent was retained, then retain
        * this data node as well.
        */

        mxmlRetain(node);
      }
    }

The resulting skeleton document tree can then be searched just like one loaded using the mxmlLoad functions. For example, a filter that reads an XHTML document from stdin and then shows the title and headings in the document would look like:

    mxml_node_t *doc, *title, *body, *heading;

    doc = mxmlSAXLoadFd(NULL, 0,
                        MXML_TEXT_CALLBACK,
                        sax_cb, NULL);

    title = mxmlFindElement(doc, doc, "title",
                            NULL, NULL,
                            MXML_DESCEND);

    if (title)
      print_children(title);

    body = mxmlFindElement(doc, doc, "body",
                           NULL, NULL,
                           MXML_DESCEND);

    if (body)
    {
      for (heading = body->child;
           heading;
           heading = heading->next)
        print_children(heading);
    }

4Using the mxmldoc Utility

This chapter describes how to use mxmldoc(1) program to automatically generate documentation from C and C++ source files.

The Basics

Originally developed to generate the Mini-XML and CUPS API documentation, mxmldoc is now a general-purpose utility which scans C and C++ source files to produce HTML and man page documentation along with an XML file representing the functions, types, and definitions in those source files. Unlike popular documentation generators like Doxygen or Javadoc, mxmldoc uses in-line comments rather than comment headers, allowing for more "natural" code documentation.

By default, mxmldoc produces HTML documentation. For example, the following command will scan all of the C source and header files in the current directory and produce a HTML documentation file called filename.html:

    mxmldoc *.h *.c >filename.html ENTER

You can also specify an XML file to create which contains all of the information from the source files. For example, the following command creates an XML file called filename.xml in addition to the HTML file:

    mxmldoc filename.xml *.h *.c >filename.html ENTER

The --no-output option disables the normal HTML output:

    mxmldoc --no-output filename.xml *.h *.c ENTER

You can then run mxmldoc again with the XML file alone to generate the HTML documentation:

    mxmldoc filename.xml >filename.html ENTER

Creating Man Pages

The --man filename option tells mxmldoc to create a man page instead of HTML documentation, for example:

    mxmldoc --man filename filename.xml \
        >filename.man ENTER

    mxmldoc --man filename *.h *.c \
        >filename.man ENTER

Creating Xcode Documentation Sets

The --docset directory.docset option tells mxmldoc to create an Xcode documentation set containing the HTML documentation, for example:

    mxmldoc --docset foo.docset *.h *.c foo.xml ENTER

Xcode documentation sets can only be built on Mac OS X with Xcode 3.0 or higher installed.

Commenting Your Code

As noted previously, mxmldoc looks for in-line comments to describe the functions, types, and constants in your code. Mxmldoc will document all public names it finds in your source files - any names starting with the underscore character (_) or names that are documented with the @private@ directive are treated as private and are undocumented.

Comments appearing directly before a function or type definition are used to document that function or type. Comments appearing after argument, definition, return type, or variable declarations are used to document that argument, definition, return type, or variable. For example, the following code excerpt defines a key/value structure and a function that creates a new instance of that structure:

    /* A key/value pair. This is used with the
       dictionary structure. */

    struct keyval
    {
      char *key; /* Key string */
      char *val; /* Value string */
    };

    /* Create a new key/value pair. */

    struct keyval * /* New key/value pair */
    new_keyval(
        const char *key, /* Key string */
	const char *val) /* Value string */
    {
      ...
    }

Mxmldoc also knows to remove extra asterisks (*) from the comment string, so the comment string:

    /*
     * Compute the value of PI.
     *
     * The function connects to an Internet server
     * that streams audio of mathematical monks
     * chanting the first 100 digits of PI.
     */

will be shown as:

    Compute the value of PI.

    The function connects to an Internet server
    that streams audio of mathematical monks
    chanting the first 100 digits of PI.

Comments can also include the following special @name ...@ directive strings:

Titles, Sections, and Introductions

Mxmldoc also provides options to set the title, section, and introduction text for the generated documentation. The --title text option specifies the title for the documentation. The title string is usually put in quotes:

    mxmldoc filename.xml \
        --title "My Famous Documentation" \
        >filename.html ENTER

The --section name option specifies the section for the documentation. For HTML documentation, the name is placed in a HTML comment such as:

    <!-- SECTION: name -->

For man pages, the section name is usually just a number ("3"), or a number followed by a vendor name ("3acme"). The section name is used in the .TH directive in the man page:

    .TH mylibrary 3acme "My Title" ...

The default section name for man page output is "3". There is no default section name for HTML output.

Finally, the --intro filename option specifies a file to embed after the title and section but before the generated documentation. For HTML documentation, the file must consist of valid HTML without the usual DOCTYPE, html, and body elements. For man page documentation, the file must consist of valid nroff(1) text.


AMini-XML License

The Mini-XML library and included programs are provided under the terms of the GNU Library General Public License version 2 (LGPL2) with the following exceptions:

  1. Static linking of applications to the Mini-XML library does not constitute a derivative work and does not require the author to provide source code for the application, use the shared Mini-XML libraries, or link their applications against a user-supplied version of Mini-XML.

    If you link the application to a modified version of Mini-XML, then the changes to Mini-XML must be provided under the terms of the LGPL2 in sections 1, 2, and 4.

  2. You do not have to provide a copy of the Mini-XML license with programs that are linked to the Mini-XML library, nor do you have to identify the Mini-XML license in your program or documentation as required by section 6 of the LGPL2.

GNU LIBRARY GENERAL PUBLIC LICENSE

Version 2, June 1991
Copyright (C) 1991 Free Software Foundation, Inc.
59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.
[This is the first released version of the library GPL. It is numbered 2 because it goes with version 2 of the ordinary GPL.]

Preamble

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That's all there is to it!


BRelease Notes

Changes in Mini-XML 2.7

Changes in Mini-XML 2.6

Changes in Mini-XML 2.5

Changes in Mini-XML 2.4

Changes in Mini-XML 2.3

Changes in Mini-XML 2.2.2

Changes in Mini-XML 2.2.1

Changes in Mini-XML 2.2

Changes in Mini-XML 2.1

Changes in Mini-XML 2.0

Changes in Mini-XML 1.3

Changes in Mini-XML 1.2

Changes in Mini-XML 1.1.2

Changes in Mini-XML 1.1.1

Changes in Mini-XML 1.1

Changes in Mini-XML 1.0

Changes in Mini-XML 0.93

Changes in Mini-XML 0.92

Changes in Mini-XML 0.91

Changes in Mini-XML 0.9


CLibrary Reference

Contents


DXML Schema

This appendix provides the XML schema that is used for the XML files produced by mxmldoc. This schema is available on-line at:

    http://www.easysw.com/~mike/mxmldoc.xsd

mxmldoc.xsd


<?xml version="1.0"?>
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema">
  <xsd:annotation>
    <xsd:documentation xml:lang="en">
      Mini-XML 2.3 documentation schema for mxmldoc output.
      Copyright 2003-2007 by Michael Sweet.
    </xsd:documentation>
  </xsd:annotation>

  <!-- basic element definitions -->
  <xsd:element name="argument" type="argumentType"/>
  <xsd:element name="class" type="classType"/>
  <xsd:element name="constant" type="constantType"/>
  <xsd:element name="description" type="xsd:string"/>
  <xsd:element name="enumeration" type="enumerationType"/>
  <xsd:element name="function" type="functionType"/>
  <xsd:element name="mxmldoc" type="mxmldocType"/>
  <xsd:element name="namespace" type="namespaceType"/>
  <xsd:element name="returnvalue" type="returnvalueType"/>
  <xsd:element name="seealso" type="identifierList"/>
  <xsd:element name="struct" type="structType"/>
  <xsd:element name="typedef" type="typedefType"/>
  <xsd:element name="type" type="xsd:string"/>
  <xsd:element name="union" type="unionType"/>
  <xsd:element name="variable" type="variableType"/>

  <!-- descriptions of complex elements -->
  <xsd:complexType name="argumentType">
    <xsd:sequence>
      <xsd:element ref="type" minOccurs="1" maxOccurs="1"/>
      <xsd:element ref="description" minOccurs="0" maxOccurs="1"/>
    </xsd:sequence>
    <xsd:attribute name="default" type="xsd:string" use="optional"/>
    <xsd:attribute name="name" type="identifier" use="required"/>
    <xsd:attribute name="direction" type="direction" use="optional"
     default="I"/>
  </xsd:complexType>

  <xsd:complexType name="classType">
    <xsd:sequence>
      <xsd:element ref="description" minOccurs="0" maxOccurs="1"/>
      <xsd:choice minOccurs="0" maxOccurs="unbounded">
	<xsd:element ref="class"/>
	<xsd:element ref="enumeration"/>
	<xsd:element ref="function"/>
	<xsd:element ref="struct"/>
	<xsd:element ref="typedef"/>
	<xsd:element ref="union"/>
	<xsd:element ref="variable"/>
      </xsd:choice>
    </xsd:sequence>
    <xsd:attribute name="name" type="identifier" use="required"/>
    <xsd:attribute name="parent" type="xsd:string" use="optional"/>
  </xsd:complexType>

  <xsd:complexType name="constantType">
    <xsd:sequence>
      <xsd:element ref="description" minOccurs="0" maxOccurs="1"/>
    </xsd:sequence>
    <xsd:attribute name="name" type="identifier" use="required"/>
  </xsd:complexType>

  <xsd:complexType name="enumerationType">
    <xsd:sequence>
      <xsd:element ref="description" minOccurs="0" maxOccurs="1"/>
      <xsd:element ref="constant" minOccurs="1" maxOccurs="unbounded"/>
    </xsd:sequence>
    <xsd:attribute name="name" type="identifier" use="required"/>
  </xsd:complexType>

  <xsd:complexType name="functionType">
    <xsd:sequence>
      <xsd:element ref="returnvalue" minOccurs="0" maxOccurs="1"/>
      <xsd:element ref="description" minOccurs="0" maxOccurs="1"/>
      <xsd:element ref="argument" minOccurs="1" maxOccurs="unbounded"/>
      <xsd:element ref="seealso" minOccurs="0" maxOccurs="1"/>
    </xsd:sequence>
    <xsd:attribute name="name" type="identifier" use="required"/>
    <xsd:attribute name="scope" type="scope" use="optional"/>
  </xsd:complexType>

  <xsd:complexType name="mxmldocType">
    <xsd:choice minOccurs="0" maxOccurs="unbounded">
      <xsd:element ref="class"/>
      <xsd:element ref="enumeration"/>
      <xsd:element ref="function"/>
      <xsd:element ref="namespace"/>
      <xsd:element ref="struct"/>
      <xsd:element ref="typedef"/>
      <xsd:element ref="union"/>
      <xsd:element ref="variable"/>
    </xsd:choice>
  </xsd:complexType>

  <xsd:complexType name="namespaceType">
    <xsd:sequence>
      <xsd:element ref="description" minOccurs="0" maxOccurs="1"/>
      <xsd:choice minOccurs="0" maxOccurs="unbounded">
	<xsd:element ref="class"/>
	<xsd:element ref="enumeration"/>
	<xsd:element ref="function"/>
	<xsd:element ref="struct"/>
	<xsd:element ref="typedef"/>
	<xsd:element ref="union"/>
	<xsd:element ref="variable"/>
      </xsd:choice>
    </xsd:sequence>
    <xsd:attribute name="name" type="identifier" use="required"/>
  </xsd:complexType>

  <xsd:complexType name="returnvalueType">
    <xsd:sequence>
      <xsd:element ref="type" minOccurs="1" maxOccurs="1"/>
      <xsd:element ref="description" minOccurs="0" maxOccurs="1"/>
    </xsd:sequence>
  </xsd:complexType>

  <xsd:complexType name="structType">
    <xsd:sequence>
      <xsd:element ref="description" minOccurs="0" maxOccurs="1"/>
      <xsd:choice minOccurs="0" maxOccurs="unbounded">
	<xsd:element ref="variable"/>
	<xsd:element ref="function"/>
      </xsd:choice>
    </xsd:sequence>
    <xsd:attribute name="name" type="identifier" use="required"/>
  </xsd:complexType>

  <xsd:complexType name="typedefType">
    <xsd:sequence>
      <xsd:element ref="type" minOccurs="1" maxOccurs="1"/>
      <xsd:element ref="description" minOccurs="0" maxOccurs="1"/>
    </xsd:sequence>
    <xsd:attribute name="name" type="identifier" use="required"/>
  </xsd:complexType>

  <xsd:complexType name="unionType">
    <xsd:sequence>
      <xsd:element ref="description" minOccurs="0" maxOccurs="1"/>
      <xsd:element ref="variable" minOccurs="0" maxOccurs="unbounded"/>
    </xsd:sequence>
    <xsd:attribute name="name" type="identifier" use="required"/>
  </xsd:complexType>

  <xsd:complexType name="variableType">
    <xsd:sequence>
      <xsd:element ref="type" minOccurs="1" maxOccurs="1"/>
      <xsd:element ref="description" minOccurs="0" maxOccurs="1"/>
    </xsd:sequence>
    <xsd:attribute name="name" type="identifier" use="required"/>
  </xsd:complexType>

  <!-- data types -->
  <xsd:simpleType name="direction">
    <xsd:restriction base="xsd:string">
      <xsd:enumeration value="I"/>
      <xsd:enumeration value="O"/>
      <xsd:enumeration value="IO"/>
    </xsd:restriction>
  </xsd:simpleType>

  <xsd:simpleType name="identifier">
    <xsd:restriction base="xsd:string">
      <xsd:pattern value="[a-zA-Z_(.]([a-zA-Z_(.,)* 0-9])*"/>
    </xsd:restriction>
  </xsd:simpleType>

  <xsd:simpleType name="identifierList">
    <xsd:list itemType="identifier"/>
  </xsd:simpleType>

  <xsd:simpleType name="scope">
    <xsd:restriction base="xsd:string">
      <xsd:enumeration value=""/>
      <xsd:enumeration value="private"/>
      <xsd:enumeration value="protected"/>
      <xsd:enumeration value="public"/>
    </xsd:restriction>
  </xsd:simpleType>
</xsd:schema>