VuoTextHtml.c

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#include "VuoTextHtml.h"
 
#include <libxml/xpath.h>
#include <libxml/HTMLparser.h>
 
#ifdef VUO_COMPILER
VuoModuleMetadata({
                      "title" : "VuoTextHtml",
                      "dependencies" : [
                          "xml2",
                          "z",
                          "VuoText"
                      ]
                  });
#endif
 
static void VuoXmlError(void *unused, xmlError *error)
{
    char *message = strdup(error->message);
    size_t len = strlen(message);
    if (message[len-1] == '\n')
        message[len-1] = 0;
 
    VUserLog("Error: %s (line %i)", message, error->line);
 
    free(message);
}
 
static void __attribute__((constructor)) init()
{
    xmlInitParser();
    xmlSetStructuredErrorFunc(NULL, VuoXmlError);
}
 
VuoText VuoText_removeHtml(VuoText text)
{
    if (!text)
        return NULL;
 
    // First check whether the text contains stuff that looks like HTML,
    // so we don't waste time parsing it if it won't change anything.
    size_t length = strlen(text);
    bool found = false;
    for (unsigned int i = 0; i < length; ++i)
        if (text[i] == '<' || text[i] == '&')
        {
            found = true;
            break;
        }
    if (!found)
        return VuoText_make(text);
 
    int options = HTML_PARSE_RECOVER | HTML_PARSE_NOERROR | HTML_PARSE_NOWARNING;
    xmlDocPtr doc = htmlReadDoc((const xmlChar *)text, "", "UTF-8", options);
    if (!doc)
    {
        // Sometimes it works on the second try.
        doc = htmlReadDoc((const xmlChar *)text, "", "UTF-8", options);
        if (!doc)
            return NULL;
    }
    VuoDefer(^{ xmlFreeDoc(doc); });
 
 
    // Remove the <style> and <script> tags.
    {
        xmlXPathContextPtr xpathContext = xmlXPathNewContext(doc);
        if (!xpathContext)
            return NULL;
        VuoDefer(^{ xmlXPathFreeContext(xpathContext); });
 
        xmlXPathObjectPtr xpathObject = xmlXPathEvalExpression((const unsigned char *)"//style|//script", xpathContext);
        if (!xpathObject)
            return NULL;
        VuoDefer(^{ xmlXPathFreeObject(xpathObject); });
 
        if (!xmlXPathNodeSetIsEmpty(xpathObject->nodesetval))
        {
            for (int i = 0; i < xpathObject->nodesetval->nodeNr; ++i)
            {
                xmlUnlinkNode(xpathObject->nodesetval->nodeTab[i]);
                xmlFree(xpathObject->nodesetval->nodeTab[i]);
                xpathObject->nodesetval->nodeTab[i] = NULL;
            }
        }
    }
 
 
    xmlNodePtr root = xmlDocGetRootElement(doc);
    xmlChar *content = xmlNodeGetContent(root);
    VuoDefer(^{ xmlFree(content); });
 
    return VuoText_make((const char *)content);
}