postgresql/contrib/xml/pgxml_dom.c

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/* Parser interface for DOM-based parser (libxml) rather than
stream-based SAX-type parser */
#include "postgres.h"
#include "fmgr.h"
/* libxml includes */
#include <libxml/xpath.h>
#include <libxml/tree.h>
#include <libxml/xmlmemory.h>
/* declarations */
static void *pgxml_palloc(size_t size);
static void *pgxml_repalloc(void *ptr, size_t size);
static void pgxml_pfree(void *ptr);
static char *pgxml_pstrdup(const char *string);
static void pgxml_parser_init();
static xmlChar *pgxmlNodeSetToText(xmlNodeSetPtr nodeset, xmlDocPtr doc,
xmlChar * toptagname, xmlChar * septagname,
int format);
static xmlChar *pgxml_texttoxmlchar(text *textstring);
Datum pgxml_parse(PG_FUNCTION_ARGS);
Datum pgxml_xpath(PG_FUNCTION_ARGS);
/* memory handling passthrough functions (e.g. palloc, pstrdup are
currently macros, and the others might become so...) */
static void *
pgxml_palloc(size_t size)
{
return palloc(size);
}
static void *
pgxml_repalloc(void *ptr, size_t size)
{
return repalloc(ptr, size);
}
static void
pgxml_pfree(void *ptr)
{
return pfree(ptr);
}
static char *
pgxml_pstrdup(const char *string)
{
return pstrdup(string);
}
static void
pgxml_parser_init()
{
/*
* This code should also set parser settings from user-supplied info.
* Quite how these settings are made is another matter :)
*/
xmlMemSetup(pgxml_pfree, pgxml_palloc, pgxml_repalloc, pgxml_pstrdup);
xmlInitParser();
}
/* Returns true if document is well-formed */
PG_FUNCTION_INFO_V1(pgxml_parse);
Datum
pgxml_parse(PG_FUNCTION_ARGS)
{
/* called as pgxml_parse(document) */
xmlDocPtr doctree;
text *t = PG_GETARG_TEXT_P(0); /* document buffer */
int32 docsize = VARSIZE(t) - VARHDRSZ;
pgxml_parser_init();
doctree = xmlParseMemory((char *) VARDATA(t), docsize);
if (doctree == NULL)
{
xmlCleanupParser();
PG_RETURN_BOOL(false); /* i.e. not well-formed */
}
xmlCleanupParser();
xmlFreeDoc(doctree);
PG_RETURN_BOOL(true);
}
static xmlChar
*
pgxmlNodeSetToText(xmlNodeSetPtr nodeset,
xmlDocPtr doc,
xmlChar * toptagname,
xmlChar * septagname,
int format)
{
/* Function translates a nodeset into a text representation */
/*
* iterates over each node in the set and calls xmlNodeDump to write
* it to an xmlBuffer -from which an xmlChar * string is returned.
*/
/* each representation is surrounded by <tagname> ... </tagname> */
/* if format==0, add a newline between nodes?? */
xmlBufferPtr buf;
xmlChar *result;
int i;
buf = xmlBufferCreate();
if ((toptagname != NULL) && (xmlStrlen(toptagname) > 0))
{
xmlBufferWriteChar(buf, "<");
xmlBufferWriteCHAR(buf, toptagname);
xmlBufferWriteChar(buf, ">");
}
if (nodeset != NULL)
{
for (i = 0; i < nodeset->nodeNr; i++)
{
if ((septagname != NULL) && (xmlStrlen(septagname) > 0))
{
xmlBufferWriteChar(buf, "<");
xmlBufferWriteCHAR(buf, septagname);
xmlBufferWriteChar(buf, ">");
}
xmlNodeDump(buf, doc, nodeset->nodeTab[i], 1, (format == 2));
if ((septagname != NULL) && (xmlStrlen(septagname) > 0))
{
xmlBufferWriteChar(buf, "</");
xmlBufferWriteCHAR(buf, septagname);
xmlBufferWriteChar(buf, ">");
}
if (format)
xmlBufferWriteChar(buf, "\n");
}
}
if ((toptagname != NULL) && (xmlStrlen(toptagname) > 0))
{
xmlBufferWriteChar(buf, "</");
xmlBufferWriteCHAR(buf, toptagname);
xmlBufferWriteChar(buf, ">");
}
result = xmlStrdup(buf->content);
xmlBufferFree(buf);
return result;
}
static xmlChar *
pgxml_texttoxmlchar(text *textstring)
{
xmlChar *res;
int32 txsize;
txsize = VARSIZE(textstring) - VARHDRSZ;
res = (xmlChar *) palloc(txsize + 1);
memcpy((char *) res, VARDATA(textstring), txsize);
res[txsize] = '\0';
return res;
}
PG_FUNCTION_INFO_V1(pgxml_xpath);
Datum
pgxml_xpath(PG_FUNCTION_ARGS)
{
xmlDocPtr doctree;
xmlXPathContextPtr ctxt;
xmlXPathObjectPtr res;
xmlChar *xpath,
*xpresstr,
*toptag,
*septag;
xmlXPathCompExprPtr comppath;
int32 docsize,
ressize;
text *t,
*xpres;
t = PG_GETARG_TEXT_P(0); /* document buffer */
xpath = pgxml_texttoxmlchar(PG_GETARG_TEXT_P(1)); /* XPath expression */
toptag = pgxml_texttoxmlchar(PG_GETARG_TEXT_P(2));
septag = pgxml_texttoxmlchar(PG_GETARG_TEXT_P(3));
docsize = VARSIZE(t) - VARHDRSZ;
pgxml_parser_init();
doctree = xmlParseMemory((char *) VARDATA(t), docsize);
if (doctree == NULL)
{ /* not well-formed */
xmlCleanupParser();
PG_RETURN_NULL();
}
ctxt = xmlXPathNewContext(doctree);
ctxt->node = xmlDocGetRootElement(doctree);
/* compile the path */
comppath = xmlXPathCompile(xpath);
if (comppath == NULL)
{
elog(WARNING, "XPath syntax error");
xmlFreeDoc(doctree);
pfree((void *) xpath);
xmlCleanupParser();
PG_RETURN_NULL();
}
/* Now evaluate the path expression. */
res = xmlXPathCompiledEval(comppath, ctxt);
xmlXPathFreeCompExpr(comppath);
if (res == NULL)
{
xmlFreeDoc(doctree);
pfree((void *) xpath);
xmlCleanupParser();
PG_RETURN_NULL(); /* seems appropriate */
}
/* now we dump this node, ?surrounding by tags? */
/* To do this, we look first at the type */
switch (res->type)
{
case XPATH_NODESET:
xpresstr = pgxmlNodeSetToText(res->nodesetval,
doctree,
toptag, septag, 0);
break;
case XPATH_STRING:
xpresstr = xmlStrdup(res->stringval);
break;
default:
elog(WARNING, "Unsupported XQuery result: %d", res->type);
xpresstr = xmlStrdup("<unsupported/>");
}
/* Now convert this result back to text */
ressize = strlen(xpresstr);
xpres = (text *) palloc(ressize + VARHDRSZ);
memcpy(VARDATA(xpres), xpresstr, ressize);
VARATT_SIZEP(xpres) = ressize + VARHDRSZ;
/* Free various storage */
xmlFreeDoc(doctree);
pfree((void *) xpath);
xmlFree(xpresstr);
xmlCleanupParser();
PG_RETURN_TEXT_P(xpres);
}