Add header bit for 'name or value is shared' flag

This is required to make it possible to use a pointer to one of the
buffers with the document data in nodes but keep offset_debug and (more
importantly) XPath document order comparison optimization working.

The change increases memory page alignment to 64 bytes (so requires +32
bytes for every page allocation, which should not be a problem - even with
non-default 4k pages this is <1% extra cost, with default 32k pages the
overhead is 0.1%)

git-svn-id: https://pugixml.googlecode.com/svn/trunk@1031 99668b35-9821-0410-8761-19e4c4f06640

2 files changed, 12 insertions, 8 deletions

diff --git a/src/pugixml.cpp b/src/pugixml.cpp
index c9f29d7..8e61182 100644
--- a/src/pugixml.cpp
+++ b/src/pugixml.cpp
@@ -266,11 +266,14 @@ PUGI__NS_BEGIN
 	#endif
 		;
 
-	static const uintptr_t xml_memory_page_alignment = 32;
+	static const uintptr_t xml_memory_page_alignment = 64;
 	static const uintptr_t xml_memory_page_pointer_mask = ~(xml_memory_page_alignment - 1);
+	static const uintptr_t xml_memory_page_name_or_value_shared_mask = 32;
 	static const uintptr_t xml_memory_page_name_allocated_mask = 16;
 	static const uintptr_t xml_memory_page_value_allocated_mask = 8;
 	static const uintptr_t xml_memory_page_type_mask = 7;
+	static const uintptr_t xml_memory_page_name_allocated_or_shared_mask = xml_memory_page_name_allocated_mask | xml_memory_page_name_or_value_shared_mask;
+	static const uintptr_t xml_memory_page_value_allocated_or_shared_mask = xml_memory_page_value_allocated_mask | xml_memory_page_name_or_value_shared_mask;
 
 	struct xml_allocator;
 
@@ -5334,13 +5337,13 @@ namespace pugi
 		case node_element:
 		case node_declaration:
 		case node_pi:
-			return (_root->header & impl::xml_memory_page_name_allocated_mask) ? -1 : _root->name - buffer;
+			return (_root->header & impl::xml_memory_page_name_allocated_or_shared_mask) ? -1 : _root->name - buffer;
 
 		case node_pcdata:
 		case node_cdata:
 		case node_comment:
 		case node_doctype:
-			return (_root->header & impl::xml_memory_page_value_allocated_mask) ? -1 : _root->value - buffer;
+			return (_root->header & impl::xml_memory_page_value_allocated_or_shared_mask) ? -1 : _root->value - buffer;
 
 		default:
 			return -1;
@@ -6830,8 +6833,8 @@ PUGI__NS_BEGIN
 
 		if (node)
 		{
-			if (node->name && (node->header & xml_memory_page_name_allocated_mask) == 0) return node->name;
-			if (node->value && (node->header & xml_memory_page_value_allocated_mask) == 0) return node->value;
+			if (node->name && (node->header & impl::xml_memory_page_name_allocated_or_shared_mask) == 0) return node->name;
+			if (node->value && (node->header & impl::xml_memory_page_value_allocated_or_shared_mask) == 0) return node->value;
 			return 0;
 		}
 
@@ -6839,8 +6842,8 @@ PUGI__NS_BEGIN
 
 		if (attr)
 		{
-			if ((attr->header & xml_memory_page_name_allocated_mask) == 0) return attr->name;
-			if ((attr->header & xml_memory_page_value_allocated_mask) == 0) return attr->value;
+			if ((attr->header & impl::xml_memory_page_name_allocated_or_shared_mask) == 0) return attr->name;
+			if ((attr->header & impl::xml_memory_page_value_allocated_or_shared_mask) == 0) return attr->value;
 			return 0;
 		}
 
diff --git a/src/pugixml.hpp b/src/pugixml.hpp
index 69b2cb2..ba480cd 100644
--- a/src/pugixml.hpp
+++ b/src/pugixml.hpp
@@ -926,7 +926,8 @@ namespace pugi
 	private:
 		char_t* _buffer;
 
-		char _memory[192];
+		// sizeof(xml_memory_page) + sizeof(xml_document_struct) + xml_memory_page_alignment + 1 void* in case compiler inserts padding
+		char _memory[sizeof(void*) * 20 + 64];
 		
 		// Non-copyable semantics
 		xml_document(const xml_document&);