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domc-0.3 released -- W3C's DOM in c

From: Michael B. Allen <mballen@erols.com>
Date: Sun, 22 Jul 2001 02:59:14 -0400
To: www-dom@w3.org
Message-ID: <20010722025914.A11361@nano.foo.net>
DOMC is a light weight implementation of the Document Object
Model (DOM) in ANSI c as specified in the W3C DOM Core Level
1 recommendation. When coupled with the Expat XML Parser
Toolkit, DOMC can load, store, build, and directly manipulate
XML documents represented as a tree in memory.

Enjoy,
Mike

Sun Jul 22 00:34:30 EDT 2001

                         DOMC
          The Document Object Model (DOM) in c

             http://auditorymodels.org/domc/

In the spirit of Expat and the community process I have
written a light weight implementation of the Document Object
Model (DOM) in ANSI c as specified in the W3C DOM Core Level1
recommendation:

  http://www.w3.org/TR/1998/REC-DOM-Level-1-19981001/level-one-core.html

under the MIT License. The package is available for immediate
download here:

  http://auditorymodels.org/domc/src/

The Document Object Model is the W3C recommended way to
manipulate XML and HTML documements as a tree of nodes. It is
the more sophisticated but more memory constraining alternative
to the SAX api.

Some functionality with respect to EntityReferences, Notations,
character encoding, and other peripherals are missing however
the package should be immediately useable in many contexts. The
goal is full compliance although HTML is not supported and I
have no plans to support it in the future. It is small (~1800
lines of code) and should prove to be highly extensible. I
strongly encourage you to contribute changes but as cited in
the MIT License you are not obligated to do so.

BUILDING:

UNIX - The package has not been prepared as a library but
the Makefile should build any of the examples and serve as a
model for how to integrate this code into your own. I suspect
in the simplest case this would be to export the appropriate
LD_LIBRARY_PATH or equivalent such as perhaps

  export LD_LIBRARY_PATH=domc_0.3/lib/

and compile with the equivalent of:

  gcc -Wall -I domc_0.3/lib -L domc_0.3/lib -lexpat \
        lib/stack.c lib/node.c lib/dom.c lib/expatls.c \
        -o my_program my_program.c

If expatls.c is left out the DOM_DocumentLS functions will
not be available but Expat will not be required to compile
(however, you will not be able to load or save to XML format
without your own serialization routines).

WINDOWS - I have never built this package on the Windows
platform but theres no reason why it shouldn't with a little
help. Some defines like DOM_String_dup will need to be replaced
with their equivalent windows functions. If you successfully
build DOMC on Windows I'm sure others would appreciate
your sending me a patch (preferably with your best guess at
conditional compilation that doesn't break the UNIX build).

THE API:

The popular C++ in c technique was NOT used. This means all
methods are expressed as functions that follow the pattern:

  DOM_Object_methodName(DOM_Object *obj, <parameters>)

where the first parameter is always the object the method is
being invoked on. Simple typedefs are used to compensate for
the lack of OO constructs in the c language. For example the
following IDL samples from the W3C specification:

  DOM_Element *DOM_Document_createElement( \
              in DOMString tagName raises(DOMException);
  NodeList getElementsByTagName(in DOMString name);
  Node appendChild(in Node newChild) raises(DOMException);

have been implemented in DOMC with the following prototypes:

  DOM_Element *DOM_Document_createElement( \
              DOM_Document *doc, const DOM_String *tagName);
  DOM_NodeList *DOM_Element_getElementsByTagName( \
              DOM_Element *element, const DOM_String *name);
  DOM_Node *DOM_Node_appendChild( \
              DOM_Node *node, DOM_Node *newChild);

I believe the only definitions in DOMC that are not specified
in the W3C documentation are the <code>DOM_Exception</code>
constants:

  #define DOM_NO_MEMORY_ERR               11
  #define DOM_NULL_POINTER_ERR            12
  #define DOM_SYSTEM_ERR                  13
  #define DOM_XML_PARSER_ERR              14

the memory management functions:

  void DOM_Document_destroyNode( \
              DOM_Document *doc, DOM_Node *node); 
  void DOM_Document_destroyNodeList(DOM_Document *doc, \
              DOM_NodeList *nl, int free_nodes);
  void DOM_Document_destroyNamedNodeMap(DOM_Document *doc, \
              DOM_NamedNodeMap *nnm, int free_nodes);

and load/save convenience operations:

  int DOM_DocumentLS_load(DOM_Document *doc, DOM_String *uri);
  int DOM_DocumentLS_save(DOM_Document *doc, \
              DOM_String *uri, DOM_Node *node);

The above load/save implementation is dependant on the Expat
XML Parser Toolkit which can be obtained from:

  http://expat.sourceforge.net/

however the source file can be left out of the compliation or
replaced with another implementation of the above methods.

All functions specified in Core Level 1 and two from Level 2
(e.g. DOM_Implementation_createDocument) have been completely
implemented minus the functionality previously mentioned.

The code should be highly portable however it has not been
compiled on any platform other than Linux. The only non-ANSI
code I can think of at the moment is the use of strdup however
this will need to be replaced with a function that checks for
invalid characters anyway.

Finally, below is an example program (something I always
look for when evaluating a new package) that was used to test
DOMC. There are several more example programs packaged with
the distribution.

--8<--

/* d4.c
 *
 * Load the XML file specified on the command line and build
 * a DOM tree returned as a DOM_Document object. Get the root
 * (yes, that union is a little strange -- doesn't happen a
 * lot) and add some new elements using a DOM_DocumentFragment
 * object. Then save the result as XML to stdout.
 */

#include <stdlib.h>
#include <stdio.h>
#include "dom.h"

int
main(int argc, char *argv[])
{
    DOM_Document *doc;
    DOM_DocumentFragment *dfrag;
    DOM_Element *root, *e0, *e1;
    DOM_Text *t0;

    if (argc < 2) {
        return EXIT_FAILURE;
    }

    doc = DOM_Implementation_createDocument(NULL, NULL, NULL);
    if (DOM_DocumentLS_load(doc, argv[1]) == 0) {
        return EXIT_FAILURE;
    }

    root = doc->u.Document.documentElement;

    dfrag = DOM_Document_createDocumentFragment(doc);
    e0 = DOM_Document_createElement(doc, "foo");
    e1 = DOM_Document_createElement(doc, "bar");
    t0 = DOM_Document_createTextNode(doc,
            "This tests the DocumentFragment operations such \
            as properly moving nodes from the DocumentFragment \
            into the children of another.");

    DOM_Node_appendChild(dfrag, e0);
    DOM_Node_appendChild(dfrag, e1);
    DOM_Node_appendChild(dfrag, t0);

    if (DOM_Node_appendChild(root->lastChild, dfrag) == NULL) {
        return EXIT_FAILURE;
    }

    if (DOM_DocumentLS_save(doc, "/dev/stdout", NULL) == 0) {
        return EXIT_FAILURE;
    }

    DOM_Document_destroyNode(doc, dfrag);
    DOM_Document_destroyNode(doc, doc);

    return EXIT_SUCCESS;
}
Received on Sunday, 22 July 2001 02:53:52 GMT

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