Implement document fragment parsing.

Introduce a notable behavior change in default parsing mode: documents without a
document element node are now considered invalid. This is technically a breaking change,
however the amount of documents it affects is very small, all parsed data still persists,
and lack of this check results in very confusing behavior in a number of cases.

In order to be able to parse documents without an element node, a fragment parsing flag is
introduced.

Parsing a buffer in fragment mode treats the buffer as a fragment of a valid XML.
As a consequence, top-level PCDATA is added to the tree; additionally, there are no
restrictions on the number of nodes -- so documents without a document element are considered
valid.

Due to the way parsing works internally, load_buffer_inplace occasionally can not preserve
the document contents if it's parsed in a fragment mode. While unfortunate, this problem is
fundamental; since the use case is relatively obscure, hopefully documenting this shortcoming
will be enough.

git-svn-id: https://pugixml.googlecode.com/svn/trunk@980 99668b35-9821-0410-8761-19e4c4f06640

1 files changed, 7 insertions, 1 deletions

diff --git a/src/pugixml.hpp b/src/pugixml.hpp
index e19a4a3..e5009fe 100644
--- a/src/pugixml.hpp
+++ b/src/pugixml.hpp
@@ -151,6 +151,10 @@ namespace pugi
 	// This flag is off by default; turning it on may result in slower parsing and more memory consumption.
 	const unsigned int parse_ws_pcdata_single = 0x0400;
 
+	// This flag determines if plain character data that does not have a parent node is added to the DOM tree, and if an empty document
+	// is a valid document. This flag is off by default.
+	const unsigned int parse_fragment = 0x0800;
+
 	// The default parsing mode.
 	// Elements, PCDATA and CDATA sections are added to the DOM tree, character/reference entities are expanded,
 	// End-of-Line characters are normalized, attribute values are normalized using CDATA normalization rules.
@@ -880,7 +884,9 @@ namespace pugi
 		status_bad_end_element,		// Parsing error occurred while parsing end element tag
 		status_end_element_mismatch,// There was a mismatch of start-end tags (closing tag had incorrect name, some tag was not closed or there was an excessive closing tag)
 
-		status_append_invalid_root	// Unable to append nodes since root type is not node_element or node_document (exclusive to xml_node::append_buffer)
+		status_append_invalid_root,	// Unable to append nodes since root type is not node_element or node_document (exclusive to xml_node::append_buffer)
+
+		status_no_document_element	// Parsing resulted in a document without element nodes
 	};
 
 	// Parsing result