mxml.html

minixml2.5最新的版本。 嵌入式xml 解析、查找、生成、遍历 功能,全部实现是标准c,移植很容易。 最新的2.5

<P>The second argument is the stdio file to write to, as opened by <TT>
fopen()</TT> or <TT>popen()</TT>. You can also use <TT>stdout</TT> if
 you are implementing an XML filter program.</P>
<P>The third argument is the whitespace callback to use when saving the
 file. Whitespace callbacks are covered in detail in <A href="SAVE_CALLBACKS">
Chapter 3</A>. The previous example code uses the <TT>MXML_NO_CALLBACK</TT>
 constant to specify that no special whitespace handling is required.</P>
<P>The <A href="#mxmlSaveAllocString"><TT>mxmlSaveAllocString</TT></A>,
 and <A href="#mxmlSaveString"><TT>mxmlSaveString</TT></A> functions
 save XML node trees to strings:</P>
<PRE>
    char buffer[8192];
    char *ptr;
    mxml_node_t *tree;

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

    ...
    ptr = mxmlSaveAllocString(tree, MXML_NO_CALLBACK);
</PRE>
<P>The first and last arguments are the same as used for <TT>
mxmlSaveFile()</TT>. The <TT>mxmlSaveString</TT> function takes pointer
 and size arguments for saving the XML document to a fixed-size buffer,
 while <TT>mxmlSaveAllocString()</TT> returns a string buffer that was
 allocated using <TT>malloc()</TT>.</P>
<H3><A NAME="3_5_1">Controlling Line Wrapping</A></H3>
<P>When saving XML documents, Mini-XML normally wraps output lines at
 column 75 so that the text is readable in terminal windows. The <A href="#mxmlSetWrapMargin">
<TT>mxmlSetWrapMargin</TT></A> function overrides the default wrap
 margin:</P>
<PRE>
    /* Set the margin to 132 columns */
    mxmlSetWrapMargin(132);

    /* Disable wrapping */
    mxmlSetWrapMargin(0);
</PRE>

<!-- NEW PAGE-->
<H2><A NAME="3_6">Finding and Iterating Nodes</A></H2>
<P>The <A href="#mxmlWalkPrev"><TT>mxmlWalkPrev</TT></A> and <A href="#mxmlWalkNext">
<TT>mxmlWalkNext</TT></A>functions can be used to iterate through the
 XML node tree:</P>
<PRE>
    mxml_node_t *node;
    
    node = mxmlWalkPrev(current, tree,
                        MXML_DESCEND);

    node = mxmlWalkNext(current, tree,
                        MXML_DESCEND);
</PRE>
<P>In addition, you can find a named element/node using the <A href="#mxmlFindElement">
<TT>mxmlFindElement</TT></A> function:</P>
<PRE>
    mxml_node_t *node;
    
    node = mxmlFindElement(tree, tree, &quot;name&quot;,
                           &quot;attr&quot;, &quot;value&quot;,
                           MXML_DESCEND);
</PRE>
<P>The <TT>name</TT>, <TT>attr</TT>, and <TT>value</TT> arguments can be
 passed as <TT>NULL</TT> to act as wildcards, e.g.:</P>

<!-- NEED 4 -->
<PRE>
    /* Find the first &quot;a&quot; element */
    node = mxmlFindElement(tree, tree, &quot;a&quot;,
                           NULL, NULL,
                           MXML_DESCEND);
</PRE>

<!-- NEED 5 -->
<PRE>
    /* Find the first &quot;a&quot; element with &quot;href&quot;
       attribute */
    node = mxmlFindElement(tree, tree, &quot;a&quot;,
                           &quot;href&quot;, NULL,
                           MXML_DESCEND);
</PRE>

<!-- NEED 6 -->
<PRE>
    /* Find the first &quot;a&quot; element with &quot;href&quot;
       to a URL */
    node = mxmlFindElement(tree, tree, &quot;a&quot;,
                           &quot;href&quot;,
                           &quot;http://www.easysw.com/&quot;,
                           MXML_DESCEND);
</PRE>

<!-- NEED 5 -->
<PRE>
    /* Find the first element with a &quot;src&quot;
       attribute */
    node = mxmlFindElement(tree, tree, NULL,
                           &quot;src&quot;, NULL,
                           MXML_DESCEND);
</PRE>

<!-- NEED 5 -->
<PRE>
    /* Find the first element with a &quot;src&quot;
       = &quot;foo.jpg&quot; */
    node = mxmlFindElement(tree, tree, NULL,
                           &quot;src&quot;, &quot;foo.jpg&quot;,
                           MXML_DESCEND);
</PRE>
<P>You can also iterate with the same function:</P>
<PRE>
    mxml_node_t *node;

    for (node = mxmlFindElement(tree, tree,
                                &quot;name&quot;,
                                NULL, NULL,
                                MXML_DESCEND);
         node != NULL;
         node = mxmlFindElement(node, tree,
                                &quot;name&quot;,
                                NULL, NULL,
                                MXML_DESCEND))
    {
      ... do something ...
    }
</PRE>

<!-- NEED 10 -->
<P>The <TT>MXML_DESCEND</TT> argument can actually be one of three
 constants:</P>
<UL>
<LI><TT>MXML_NO_DESCEND</TT> means to not to look at any child nodes in
 the element hierarchy, just look at siblings at the same level or
 parent nodes until the top node or top-of-tree is reached.
<P>The previous node from &quot;group&quot; would be the &quot;node&quot; element to the
 left, while the next node from &quot;group&quot; would be the &quot;node&quot; element to
 the right.
<BR>
<BR></P>
</LI>
<LI><TT>MXML_DESCEND_FIRST</TT> means that it is OK to descend to the
 first child of a node, but not to descend further when searching.
 You'll normally use this when iterating through direct children of a
 parent node, e.g. all of the &quot;node&quot; and &quot;group&quot; elements under the
 &quot;?xml&quot; parent node in the example above.
<P>This mode is only applicable to the search function; the walk
 functions treat this as <TT>MXML_DESCEND</TT> since every call is a
 first time.
<BR>
<BR></P>
</LI>
<LI><TT>MXML_DESCEND</TT> means to keep descending until you hit the
 bottom of the tree. The previous node from &quot;group&quot; would be the &quot;val3&quot;
 node and the next node would be the first node element under &quot;group&quot;.
<P>If you were to walk from the root node &quot;?xml&quot; to the end of the tree
 with <TT>mxmlWalkNext()</TT>, the order would be:</P>
<P><TT>?xml data node val1 node val2 node val3 group node val4 node val5
 node val6 node val7 node val8</TT></P>
<P>If you started at &quot;val8&quot; and walked using <TT>mxmlWalkPrev()</TT>,
 the order would be reversed, ending at &quot;?xml&quot;.</P>
</LI>
</UL>
<HR NOSHADE>
<H1 align="right"><A name="ADVANCED"><IMG align="right" alt="3" height="100"
hspace="10" src="3.gif" width="100"></A>More Mini-XML Programming
 Techniques</H1>
<P>This chapter shows additional ways to use the Mini-XML library in
 your programs.</P>
<H2><A name="LOAD_CALLBACKS">Load Callbacks</A></H2>
<P><A href="#LOAD_XML">Chapter 2</A> introduced the <A href="#mxmlLoadFile">
<TT>mxmlLoadFile()</TT></A> and <A href="#mxmlLoadString"><TT>
mxmlLoadString()</TT></A> 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.</P>
<P>Mini-XML defines several standard callbacks for simple XML data
 files:</P>
<UL>
<LI><TT>MXML_INTEGER_CALLBACK</TT> - All data nodes contain
 whitespace-separated integers.</LI>
<LI><TT>MXML_OPAQUE_CALLBACK</TT> - All data nodes contain opaque
 strings (&quot;CDATA&quot;).</LI>
<LI><TT>MXML_REAL_CALLBACK</TT> - All data nodes contain
 whitespace-separated floating-point numbers.</LI>
<LI><TT>MXML_TEXT_CALLBACK</TT> - All data nodes contain
 whitespace-separated strings.</LI>
</UL>
<P>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: <TT>MXML_INTEGER</TT>, <TT>MXML_OPAQUE</TT>, <TT>
MXML_REAL</TT>, or <TT>MXML_TEXT</TT>. The function is called<I> after</I>
 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.</P>

<!-- NEED 2in -->
<P>The following callback function looks for an attribute named &quot;type&quot;
 or the element name to determine the value type for its child nodes:</P>
<PRE>
    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, &quot;type&quot;);
      if (type == NULL)
	type = node-&gt;value.element.name;

      if (!strcmp(type, &quot;integer&quot;))
	return (MXML_INTEGER);
      else if (!strcmp(type, &quot;opaque&quot;))
	return (MXML_OPAQUE);
      else if (!strcmp(type, &quot;real&quot;))
	return (MXML_REAL);
      else
	return (MXML_TEXT);
    }
</PRE>
<P>To use this callback function, simply use the name when you call any
 of the load functions:</P>
<PRE>
    FILE *fp;
    mxml_node_t *tree;

    fp = fopen(&quot;filename.xml&quot;, &quot;r&quot;);
    tree = mxmlLoadFile(NULL, fp, <B>type_cb</B>);
    fclose(fp);
</PRE>
<H2><A name="SAVE_CALLBACKS">Save Callbacks</A></H2>
<P><A href="#LOAD_XML">Chapter 2</A> also introduced the <A href="#mxmlSaveFile">
<TT>mxmlSaveFile()</TT></A>, <A href="#mxmlSaveString"><TT>
mxmlSaveString()</TT></A>, and <A href="#mxmlSaveAllocString"><TT>
mxmlSaveAllocString()</TT></A> functions. The last argument to these
 functions is a callback function which is used to automatically insert
 whitespace in an XML document.</P>
<P>Your callback function will be called up to four times for each
 element node with a pointer to the node and a &quot;where&quot; value of <TT>
MXML_WS_BEFORE_OPEN</TT>, <TT>MXML_WS_AFTER_OPEN</TT>, <TT>
MXML_WS_BEFORE_CLOSE</TT>, or <TT>MXML_WS_AFTER_CLOSE</TT>. The callback
 function should return <TT>NULL</TT> if no whitespace should be added
 and the string to insert (spaces, tabs, carriage returns, and newlines)
 otherwise.</P>
<P>The following whitespace callback can be used to add whitespace to
 XHTML output to make it more readable in a standard text editor:</P>
<PRE>
    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-&gt;value.element.name;

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

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

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

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

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

      return (NULL);
    }
</PRE>
<P>To use this callback function, simply use the name when you call any
 of the save functions:</P>
<PRE>