+// Encoding of the XML Document :\r
+// The following TAGs and IDs are fixed, "" is the tag of the root.\r
+// a TextNode is represented by a leaf <<$>></<$>> The DocId in the TextCollection\r
+// of that leaf is kept in a bit sequence.\r
+// a TextNode below an attribute is likewise represented by a leaf <<@$>><</@$>>\r
+// An element <e a1="v1" a2="v2" ... an="vn" > ...</e> the representation is:\r
+// <e><<@>> <<@>a1> <<$@>>DocID(v1)</<$@>></<@>a1> ... </<@>> .... </e>\r
+// Hence the attributes (if any) are always below the first child of their element,\r
+// as the children of a fake node <@>.\r
+\r
+\r
+#define DOCUMENT_OPEN_TAG ""\r
+#define DOCUMENT_TAG_ID 0\r
+#define ATTRIBUTE_OPEN_TAG "<@>"\r
+#define ATTRIBUTE_TAG_ID 1\r
+#define PCDATA_OPEN_TAG "<$>"\r
+#define PCDATA_TAG_ID 2\r
+#define ATTRIBUTE_DATA_OPEN_TAG "<@$>"\r
+#define ATTRIBUTE_DATA_TAG_ID 3\r
+#define CLOSING_TAG "</>"\r
+#define CLOSING_TAG_ID 4\r
+#define DOCUMENT_CLOSE_TAG "/"\r
+#define ATTRIBUTE_CLOSE_TAG "/<@>"\r
+#define PCDATA_CLOSE_TAG "/<$>"\r
+#define ATTRIBUTE_DATA_CLOSE_TAG "/<@$>"\r
+\r
+\r
+typedef std::unordered_set<int> TagIdSet;\r
+typedef std::unordered_map<std::string,int> TagIdMap;\r
+typedef TagIdMap::const_iterator TagIdMapIT;\r
+\r
+#define REGISTER_TAG(v,h,t) do { (h)->insert(std::make_pair((t),(v)->size()));\\r
+ (v)->push_back(t); } while (false)\r
+\r
+\r
+// returns NULLT if the test is true\r
+#define NULLT_IF(x) do { if (x) return NULLT; } while (0)\r
+\r
+\r