Don't mangle xml and xpath unless xml is not in fact a well-formed document, in xpath...

diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
index e3cd95bedd41402ba08e2dcd8997cc3cb9c1e850..a407b4a9000f11c207bf4723e388a2ecebbffdbb 100644 (file)
--- a/src/backend/utils/adt/xml.c
+++ b/src/backend/utils/adt/xml.c
@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2008, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.68.2.6 2008/11/10 18:02:27 tgl Exp $
+ * $PostgreSQL: pgsql/src/backend/utils/adt/xml.c,v 1.68.2.7 2009/02/28 19:13:28 adunstan Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -3320,41 +3320,15 @@ xpath(PG_FUNCTION_ARGS)
 
    xml_init();
 
-   /*
-    * To handle both documents and fragments, regardless of the fact whether
-    * the XML datum has a single root (XML well-formedness), we wrap the XML
-    * datum in a dummy element (<x>...</x>) and extend the XPath expression
-    * accordingly.  To do it, throw away the XML prolog, if any.
-    */
-   if (len >= 5 &&
-       xmlStrncmp((xmlChar *) datastr, (xmlChar *) "<?xml", 5) == 0)
-   {
-       i = 5;
-       while (i < len &&
-              !(datastr[i - 1] == '?' && datastr[i] == '>'))
-           i++;
-
-       if (i == len)
-           xml_ereport(ERROR, ERRCODE_INTERNAL_ERROR,
-                       "could not parse XML data");
-
-       ++i;
-
-       datastr += i;
-       len -= i;
-   }
+   /* These extra chars for string and xpath_expr allow for hacks below */
 
    string = (xmlChar *) palloc((len + 8) * sizeof(xmlChar));
-   memcpy(string, "<x>", 3);
-   memcpy(string + 3, datastr, len);
-   memcpy(string + 3 + len, "</x>", 5);
-   len += 7;
 
-   xpath_expr = (xmlChar *) palloc((xpath_len + 3) * sizeof(xmlChar));
-   memcpy(xpath_expr, "/x", 2);
-   memcpy(xpath_expr + 2, VARDATA(xpath_expr_text), xpath_len);
-   xpath_expr[xpath_len + 2] = '\0';
-   xpath_len += 2;
+   xpath_expr = (xmlChar *) palloc((xpath_len + 5) * sizeof(xmlChar));
+
+   memcpy (string, datastr, len);
+   string[len] = '\0';
+   
 
    xmlInitParser();
 
@@ -3367,9 +3341,74 @@ xpath(PG_FUNCTION_ARGS)
        xml_ereport(ERROR, ERRCODE_OUT_OF_MEMORY,
                    "could not allocate parser context");
    doc = xmlCtxtReadMemory(ctxt, (char *) string, len, NULL, NULL, 0);
-   if (doc == NULL)
-       xml_ereport(ERROR, ERRCODE_INVALID_XML_DOCUMENT,
-                   "could not parse XML data");
+
+   if (doc == NULL || xmlDocGetRootElement(doc) == NULL)
+   {
+
+       /*
+        * In case we have a fragment rather than a well-formed XML document,
+        * which has a single root (XML well-formedness), we try again after
+        * transforming the xml by stripping away the XML prolog, if any, and
+        * wrapping the remainder in a dummy element (<x>...</x>),
+        * and later extending the XPath expression accordingly. 
+        */
+       if (len >= 5 &&
+           xmlStrncmp((xmlChar *) datastr, (xmlChar *) "<?xml", 5) == 0)
+       {
+           i = 5;
+           while (i < len &&
+                  !(datastr[i - 1] == '?' && datastr[i] == '>'))
+               i++;
+           
+           if (i == len)
+               xml_ereport(ERROR, ERRCODE_INTERNAL_ERROR,
+                           "could not parse XML data");
+           
+           ++i;
+           
+           datastr += i;
+           len -= i;
+       }
+
+       memcpy(string, "<x>", 3);
+       memcpy(string + 3, datastr, len);
+       memcpy(string + 3 + len, "</x>", 5);
+       len += 7;
+
+       doc = xmlCtxtReadMemory(ctxt, (char *) string, len, NULL, NULL, 0);
+
+       if (doc == NULL)
+           xml_ereport(ERROR, ERRCODE_INVALID_XML_DOCUMENT,
+                       "could not parse XML data");
+
+       /* we already know xpath_len > 0 - see above , so this test is safe */
+
+       if (*VARDATA(xpath_expr_text) == '/')
+       {
+           memcpy(xpath_expr, "/x", 2);
+           memcpy(xpath_expr + 2, VARDATA(xpath_expr_text), xpath_len);
+           xpath_expr[xpath_len + 2] = '\0';
+           xpath_len += 2;
+       }
+       else
+       {
+           memcpy(xpath_expr, "/x//", 4);
+           memcpy(xpath_expr + 4, VARDATA(xpath_expr_text), xpath_len);
+           xpath_expr[xpath_len + 4] = '\0';
+           xpath_len += 4;
+       }
+
+   }
+   else
+   {
+       /* 
+        * if we didn't need to mangle the XML, we don't need to mangle the
+        * xpath either.
+        */
+       memcpy(xpath_expr, VARDATA(xpath_expr_text), xpath_len);
+       xpath_expr[xpath_len] = '\0';
+   }
+
    xpathctx = xmlXPathNewContext(doc);
    if (xpathctx == NULL)
        xml_ereport(ERROR, ERRCODE_OUT_OF_MEMORY,