[libxml2]Add libxml2 library

2026-07-26 16:57:28 +08:00
parent 0a44ec8a06
commit e841ac915d
3790 changed files with 668244 additions and 0 deletions
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+/** 
+ * section: 	XPath
+ * synopsis: 	Load a document, locate subelements with XPath, modify
+ *              said elements and save the resulting document.
+ * purpose: 	Shows how to make a full round-trip from a load/edit/save
+ * usage:	xpath2 <xml-file> <xpath-expr> <new-value>
+ * test:	xpath2 test3.xml '//discarded' discarded > xpath2.tmp && diff xpath2.tmp $(srcdir)/xpath2.res
+ * author: 	Aleksey Sanin and Daniel Veillard
+ * copy: 	see Copyright for the status of this software.
+ */
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <assert.h>
+
+#include <libxml/tree.h>
+#include <libxml/parser.h>
+#include <libxml/xpath.h>
+#include <libxml/xpathInternals.h>
+
+#if defined(LIBXML_XPATH_ENABLED) && defined(LIBXML_SAX1_ENABLED) && \
+    defined(LIBXML_OUTPUT_ENABLED)
+
+
+static void usage(const char *name);
+static int example4(const char *filename, const xmlChar * xpathExpr,
+                    const xmlChar * value);
+static void update_xpath_nodes(xmlNodeSetPtr nodes, const xmlChar * value);
+
+
+int 
+main(int argc, char **argv) {
+    /* Parse command line and process file */
+    if (argc != 4) {
+	fprintf(stderr, "Error: wrong number of arguments.\n");
+	usage(argv[0]);
+	return(-1);
+    } 
+    
+    /* Init libxml */     
+    xmlInitParser();
+    LIBXML_TEST_VERSION
+
+    /* Do the main job */
+    if (example4(argv[1], BAD_CAST argv[2], BAD_CAST argv[3])) {
+	usage(argv[0]);
+	return(-1);
+    }
+
+    return 0;
+}
+
+/**
+ * usage:
+ * @name:		the program name.
+ *
+ * Prints usage information.
+ */
+static void 
+usage(const char *name) {
+    assert(name);
+    
+    fprintf(stderr, "Usage: %s <xml-file> <xpath-expr> <value>\n", name);
+}
+
+/**
+ * example4:
+ * @filename:		the input XML filename.
+ * @xpathExpr:		the xpath expression for evaluation.
+ * @value:		the new node content.
+ *
+ * Parses input XML file, evaluates XPath expression and update the nodes
+ * then print the result.
+ *
+ * Returns 0 on success and a negative value otherwise.
+ */
+static int 
+example4(const char* filename, const xmlChar* xpathExpr, const xmlChar* value) {
+    xmlDocPtr doc;
+    xmlXPathContextPtr xpathCtx; 
+    xmlXPathObjectPtr xpathObj; 
+    
+    assert(filename);
+    assert(xpathExpr);
+    assert(value);
+
+    /* Load XML document */
+    doc = xmlParseFile(filename);
+    if (doc == NULL) {
+	fprintf(stderr, "Error: unable to parse file \"%s\"\n", filename);
+	return(-1);
+    }
+
+    /* Create xpath evaluation context */
+    xpathCtx = xmlXPathNewContext(doc);
+    if(xpathCtx == NULL) {
+        fprintf(stderr,"Error: unable to create new XPath context\n");
+        xmlFreeDoc(doc); 
+        return(-1);
+    }
+    
+    /* Evaluate xpath expression */
+    xpathObj = xmlXPathEvalExpression(xpathExpr, xpathCtx);
+    if(xpathObj == NULL) {
+        fprintf(stderr,"Error: unable to evaluate xpath expression \"%s\"\n", xpathExpr);
+        xmlXPathFreeContext(xpathCtx); 
+        xmlFreeDoc(doc); 
+        return(-1);
+    }
+
+    /* update selected nodes */
+    update_xpath_nodes(xpathObj->nodesetval, value);
+
+    
+    /* Cleanup of XPath data */
+    xmlXPathFreeObject(xpathObj);
+    xmlXPathFreeContext(xpathCtx); 
+
+    /* dump the resulting document */
+    xmlDocDump(stdout, doc);
+
+
+    /* free the document */
+    xmlFreeDoc(doc); 
+    
+    return(0);
+}
+
+/**
+ * update_xpath_nodes:
+ * @nodes:		the nodes set.
+ * @value:		the new value for the node(s)
+ *
+ * Prints the @nodes content to @output.
+ */
+static void
+update_xpath_nodes(xmlNodeSetPtr nodes, const xmlChar* value) {
+    int size;
+    int i;
+    
+    assert(value);
+    size = (nodes) ? nodes->nodeNr : 0;
+    
+    /*
+     * NOTE: the nodes are processed in reverse order, i.e. reverse document
+     *       order because xmlNodeSetContent can actually free up descendant
+     *       of the node and such nodes may have been selected too ! Handling
+     *       in reverse order ensure that descendant are accessed first, before
+     *       they get removed. Mixing XPath and modifications on a tree must be
+     *       done carefully !
+     */
+    for(i = size - 1; i >= 0; i--) {
+	assert(nodes->nodeTab[i]);
+	
+	xmlNodeSetContent(nodes->nodeTab[i], value);
+	/*
+	 * All the elements returned by an XPath query are pointers to
+	 * elements from the tree *except* namespace nodes where the XPath
+	 * semantic is different from the implementation in libxml2 tree.
+	 * As a result when a returned node set is freed when
+	 * xmlXPathFreeObject() is called, that routine must check the
+	 * element type. But node from the returned set may have been removed
+	 * by xmlNodeSetContent() resulting in access to freed data.
+	 * This can be exercised by running
+	 *       valgrind xpath2 test3.xml '//discarded' discarded
+	 * There is 2 ways around it:
+	 *   - make a copy of the pointers to the nodes from the result set 
+	 *     then call xmlXPathFreeObject() and then modify the nodes
+	 * or
+	 *   - remove the reference to the modified nodes from the node set
+	 *     as they are processed, if they are not namespace nodes.
+	 */
+	if (nodes->nodeTab[i]->type != XML_NAMESPACE_DECL)
+	    nodes->nodeTab[i] = NULL;
+    }
+}
+
+#else
+int main(void) {
+    fprintf(stderr, "XPath support not compiled in\n");
+    return 0;
+}
+#endif