348 lines
6.9 KiB
C
348 lines
6.9 KiB
C
/********************************************************
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* Interface code to parse an XML document using expat
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********************************************************/
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#include "postgres.h"
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#include "fmgr.h"
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#include "expat.h"
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#include "pgxml.h"
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/* Memory management - we make expat use standard pg MM */
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XML_Memory_Handling_Suite mhs;
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/* passthrough functions (palloc is a macro) */
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static void *
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pgxml_palloc(size_t size)
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{
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return palloc(size);
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}
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static void *
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pgxml_repalloc(void *ptr, size_t size)
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{
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return repalloc(ptr, size);
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}
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static void
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pgxml_pfree(void *ptr)
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{
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return pfree(ptr);
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}
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static void
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pgxml_mhs_init()
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{
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mhs.malloc_fcn = pgxml_palloc;
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mhs.realloc_fcn = pgxml_repalloc;
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mhs.free_fcn = pgxml_pfree;
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}
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static void
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pgxml_handler_init()
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{
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/*
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* This code should set up the relevant handlers from user-supplied
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* settings. Quite how these settings are made is another matter :)
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*/
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}
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/* Returns true if document is well-formed */
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PG_FUNCTION_INFO_V1(pgxml_parse);
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Datum
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pgxml_parse(PG_FUNCTION_ARGS)
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{
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/* called as pgxml_parse(document) */
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XML_Parser p;
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text *t = PG_GETARG_TEXT_P(0); /* document buffer */
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int32 docsize = VARSIZE(t) - VARHDRSZ;
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pgxml_mhs_init();
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pgxml_handler_init();
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p = XML_ParserCreate_MM(NULL, &mhs, NULL);
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if (!p)
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{
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elog(ERROR, "pgxml: Could not create expat parser");
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PG_RETURN_NULL(); /* seems appropriate if we couldn't parse */
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}
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if (!XML_Parse(p, (char *) VARDATA(t), docsize, 1))
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{
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/*
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* elog(WARNING, "Parse error at line %d:%s",
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* XML_GetCurrentLineNumber(p),
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* XML_ErrorString(XML_GetErrorCode(p)));
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*/
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XML_ParserFree(p);
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PG_RETURN_BOOL(false);
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}
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XML_ParserFree(p);
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PG_RETURN_BOOL(true);
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}
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/* XPath handling functions */
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/* XPath support here is for a very skeletal kind of XPath!
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It was easy to program though... */
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/* This first is the core function that builds a result set. The
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actual functions called by the user manipulate that result set
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in various ways.
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*/
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static XPath_Results *
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build_xpath_results(text *doc, text *pathstr)
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{
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XPath_Results *xpr;
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char *res;
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pgxml_udata *udata;
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XML_Parser p;
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int32 docsize;
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xpr = (XPath_Results *) palloc((sizeof(XPath_Results)));
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memset((void *) xpr, 0, sizeof(XPath_Results));
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xpr->rescount = 0;
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docsize = VARSIZE(doc) - VARHDRSZ;
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/* res isn't going to be the real return type, it is just a buffer */
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res = (char *) palloc(docsize);
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memset((void *) res, 0, docsize);
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xpr->resbuf = res;
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udata = (pgxml_udata *) palloc((sizeof(pgxml_udata)));
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memset((void *) udata, 0, sizeof(pgxml_udata));
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udata->currentpath[0] = '\0';
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udata->textgrab = 0;
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udata->path = (char *) palloc(VARSIZE(pathstr));
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memcpy(udata->path, VARDATA(pathstr), VARSIZE(pathstr) - VARHDRSZ);
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udata->path[VARSIZE(pathstr) - VARHDRSZ] = '\0';
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udata->resptr = res;
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udata->reslen = 0;
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udata->xpres = xpr;
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/* Now fire up the parser */
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pgxml_mhs_init();
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p = XML_ParserCreate_MM(NULL, &mhs, NULL);
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if (!p)
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{
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elog(ERROR, "pgxml: Could not create expat parser");
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pfree(xpr);
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pfree(udata->path);
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pfree(udata);
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pfree(res);
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return NULL;
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}
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XML_SetUserData(p, (void *) udata);
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/* Set the handlers */
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XML_SetElementHandler(p, pgxml_starthandler, pgxml_endhandler);
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XML_SetCharacterDataHandler(p, pgxml_charhandler);
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if (!XML_Parse(p, (char *) VARDATA(doc), docsize, 1))
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{
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/*
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* elog(WARNING, "Parse error at line %d:%s",
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* XML_GetCurrentLineNumber(p),
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* XML_ErrorString(XML_GetErrorCode(p)));
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*/
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XML_ParserFree(p);
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pfree(xpr);
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pfree(udata->path);
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pfree(udata);
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return NULL;
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}
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pfree(udata->path);
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pfree(udata);
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XML_ParserFree(p);
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return xpr;
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}
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PG_FUNCTION_INFO_V1(pgxml_xpath);
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Datum
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pgxml_xpath(PG_FUNCTION_ARGS)
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{
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/* called as pgxml_xpath(document,pathstr, index) for the moment */
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XPath_Results *xpresults;
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text *restext;
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text *t = PG_GETARG_TEXT_P(0); /* document buffer */
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text *t2 = PG_GETARG_TEXT_P(1);
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int32 ind = PG_GETARG_INT32(2) - 1;
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xpresults = build_xpath_results(t, t2);
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/*
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* This needs to be changed depending on the mechanism for returning
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* our set of results.
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*/
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if (xpresults == NULL) /* parse error (not WF or parser failure) */
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PG_RETURN_NULL();
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if (ind >= (xpresults->rescount))
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PG_RETURN_NULL();
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restext = (text *) palloc(xpresults->reslens[ind] + VARHDRSZ);
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memcpy(VARDATA(restext), xpresults->results[ind], xpresults->reslens[ind]);
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VARATT_SIZEP(restext) = xpresults->reslens[ind] + VARHDRSZ;
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pfree(xpresults->resbuf);
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pfree(xpresults);
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PG_RETURN_TEXT_P(restext);
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}
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static void
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pgxml_pathcompare(void *userData)
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{
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char *matchpos;
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matchpos = strstr(UD->currentpath, UD->path);
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if (matchpos == NULL)
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{ /* Should we have more logic here ? */
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if (UD->textgrab)
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{
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UD->textgrab = 0;
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pgxml_finalisegrabbedtext(userData);
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}
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return;
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}
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/*
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* OK, we have a match of some sort. Now we need to check that our
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* match is anchored to the *end* of the string AND that it is
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* immediately preceded by a '/'
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*/
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/*
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* This test wouldn't work if strlen (UD->path) overran the length of
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* the currentpath, but that's not possible because we got a match!
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*/
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if ((matchpos + strlen(UD->path))[0] == '\0')
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{
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if ((UD->path)[0] == '/')
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{
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if (matchpos == UD->currentpath)
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UD->textgrab = 1;
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}
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else
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{
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if ((matchpos - 1)[0] == '/')
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UD->textgrab = 1;
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}
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}
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}
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static void
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pgxml_starthandler(void *userData, const XML_Char * name,
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const XML_Char ** atts)
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{
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char sepstr[] = "/";
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if ((strlen(name) + strlen(UD->currentpath)) > MAXPATHLENGTH - 2)
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elog(WARNING, "Path too long");
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else
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{
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strncat(UD->currentpath, sepstr, 1);
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strcat(UD->currentpath, name);
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}
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if (UD->textgrab)
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{
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/*
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* Depending on user preference, should we "reconstitute" the
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* element into the result text?
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*/
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}
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else
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pgxml_pathcompare(userData);
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}
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static void
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pgxml_endhandler(void *userData, const XML_Char * name)
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{
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/*
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* Start by removing the current element off the end of the
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* currentpath
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*/
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char *sepptr;
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sepptr = strrchr(UD->currentpath, '/');
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if (sepptr == NULL)
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{
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elog(ERROR, "There's a problem...");
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sepptr = UD->currentpath;
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}
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if (strcmp(name, sepptr + 1) != 0)
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{
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elog(WARNING, "Wanted [%s], got [%s]", sepptr, name);
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/* unmatched entry, so do nothing */
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}
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else
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{
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sepptr[0] = '\0'; /* Chop that element off the end */
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}
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if (UD->textgrab)
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pgxml_pathcompare(userData);
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}
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static void
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pgxml_charhandler(void *userData, const XML_Char * s, int len)
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{
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if (UD->textgrab)
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{
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if (len > 0)
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{
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memcpy(UD->resptr, s, len);
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UD->resptr += len;
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UD->reslen += len;
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}
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}
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}
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/* Should I be using PG list types here? */
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static void
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pgxml_finalisegrabbedtext(void *userData)
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{
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/* In res/reslen, we have a single result. */
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UD->xpres->results[UD->xpres->rescount] = UD->resptr - UD->reslen;
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UD->xpres->reslens[UD->xpres->rescount] = UD->reslen;
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UD->reslen = 0;
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UD->xpres->rescount++;
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/*
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* This effectively concatenates all the results together but we do
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* know where one ends and the next begins
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*/
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}
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