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Thanks to the generous support of Torchbox (http://www.torchbox.com), I

Browse Source 
have been able to significantly improve the contrib/xml XPath
integration code.

New features:

* XPath set-returning function allows multiple results from an several
XPath queries to be used as a virtual table.
* Using libxslt, XSLT transformations (with and without parameters) are
supported. (Caution: This support allows generic URL fetching from
within the backend as well).

I've removed the old code so that it is all libxml based. Rather than
attach as a patch, I've put the tar.gz (10k!) at
http://www.azuli.co.uk/pgxml-1.0.tar.gz
(all files in archive are xml/....).

I think this is worth replacing the contrib version with, even though
the function names have changed (though the same functionality is
there), because it includes a SRF and some SPI usage, in addition to
linking to an external library. And it isn't a big module! Obviously, I
understand that people might prefer to move it elsewhere, or might have
reservations about replacing an existing contrib module with an
incompatible one. I'm open to suggestions.

John Gray
This commit is contained in:
Bruce Momjian
2004-03-05 03:24:50 +00:00
parent 1973971821
commit adca025c9e
10 changed files with 1305 additions and 862 deletions
Download Patch File Download Diff File Expand all files Collapse all files

265
contrib/xml/pgxml_dom.c
View File

@ -1,265 +0,0 @@
/* 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);
}