Changed memory management so that the document node lives inside document; this way a default-constructed document does not allocate any dynamic memory

git-svn-id: http://pugixml.googlecode.com/svn/trunk@445 99668b35-9821-0410-8761-19e4c4f06640

2 files changed, 73 insertions, 84 deletions

diff --git a/src/pugixml.cpp b/src/pugixml.cpp
index 60e0b2f..ff2be33 100644
--- a/src/pugixml.cpp
+++ b/src/pugixml.cpp
@@ -238,12 +238,47 @@ namespace pugi
 

 namespace pugi

 {

+	static const size_t xml_memory_page_size = 32768;

+

 	static const uintptr_t xml_memory_page_alignment = 32;

 	static const uintptr_t xml_memory_page_pointer_mask = ~(xml_memory_page_alignment - 1);

 	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;

 

+	struct xml_allocator;

+

+	struct xml_memory_page

+	{

+		static xml_memory_page* construct(void* memory)

+		{

+			if (!memory) return 0;

+

+			xml_memory_page* result = static_cast<xml_memory_page*>(memory);

+

+			result->allocator = 0;

+			result->memory = 0;

+			result->prev = 0;

+			result->next = 0;

+			result->busy_size = 0;

+			result->freed_size = 0;

+

+			return result;

+		}

+

+		xml_allocator* allocator;

+

+		void* memory;

+

+		xml_memory_page* prev;

+		xml_memory_page* next;

+

+		size_t busy_size;

+		size_t freed_size;

+

+		char data[1];

+	};

+

 	struct xml_memory_string_header

 	{

 		xml_memory_page* page;

@@ -258,13 +293,7 @@ namespace pugi
 

 		xml_memory_page* allocate_page(size_t data_size)

 		{

-		#ifdef __GNUC__

-			// To avoid offsetof warning (xml_memory_page is not POD)

-			xml_memory_page* dummy_page = 0;

-			size_t size = ((size_t)(uintptr_t)&dummy_page->data) + data_size;

-		#else

 			size_t size = offsetof(xml_memory_page, data) + data_size;

-		#endif

 

 			// allocate block with some alignment, leaving memory for worst-case padding

 			void* memory = global_allocate(size + xml_memory_page_alignment);

@@ -273,7 +302,7 @@ namespace pugi
 			void* page_memory = reinterpret_cast<void*>((reinterpret_cast<uintptr_t>(memory) + (xml_memory_page_alignment - 1)) & ~(xml_memory_page_alignment - 1));

 

 			// prepare page structure

-			xml_memory_page* page = new (page_memory) xml_memory_page();

+			xml_memory_page* page = xml_memory_page::construct(page_memory);

 

 			page->memory = memory;

 			page->allocator = _root->allocator;

@@ -451,6 +480,13 @@ namespace pugi
 		xml_allocator allocator;

 		const char_t* buffer;

 	};

+

+	inline xml_allocator& get_allocator(const xml_node_struct* node)

+	{

+		assert(node);

+

+		return *reinterpret_cast<xml_memory_page*>(node->header & xml_memory_page_pointer_mask)->allocator;

+	}

 }

 

 // Low-level DOM operations

@@ -3305,13 +3341,6 @@ namespace pugi
 		return !_root;

 	}

 	

-	xml_allocator& xml_node::get_allocator() const

-	{

-		assert(_root);

-

-		return *reinterpret_cast<xml_memory_page*>(_root->header & xml_memory_page_pointer_mask)->allocator;

-	}

-

 	const char_t* xml_node::name() const

 	{

 		return (_root && _root->name) ? _root->name : PUGIXML_TEXT("");

@@ -3524,7 +3553,7 @@ namespace pugi
 	{

 		if (type() != node_element && type() != node_declaration) return xml_attribute();

 		

-		xml_attribute a(append_attribute_ll(_root, get_allocator()));

+		xml_attribute a(append_attribute_ll(_root, get_allocator(_root)));

 		a.set_name(name);

 		

 		return a;

@@ -3541,7 +3570,7 @@ namespace pugi
 

 		if (cur != _root->first_attribute) return xml_attribute();

 

-		xml_attribute a(allocate_attribute(get_allocator()));

+		xml_attribute a(allocate_attribute(get_allocator(_root)));

 		a.set_name(name);

 

 		if (attr._attr->prev_attribute_c->next_attribute)

@@ -3567,7 +3596,7 @@ namespace pugi
 

 		if (cur != _root->first_attribute) return xml_attribute();

 

-		xml_attribute a(allocate_attribute(get_allocator()));

+		xml_attribute a(allocate_attribute(get_allocator(_root)));

 		a.set_name(name);

 

 		if (attr._attr->next_attribute)

@@ -3616,7 +3645,7 @@ namespace pugi
 	{

 		if ((this->type() != node_element && this->type() != node_document) || type == node_document || type == node_null) return xml_node();

 		

-		return xml_node(append_node(_root, get_allocator(), type));

+		return xml_node(append_node(_root, get_allocator(_root), type));

 	}

 

 	xml_node xml_node::insert_child_before(xml_node_type type, const xml_node& node)

@@ -3624,7 +3653,7 @@ namespace pugi
 		if ((this->type() != node_element && this->type() != node_document) || type == node_document || type == node_null) return xml_node();

 		if (node.parent() != *this) return xml_node();

 	

-		xml_node n(allocate_node(get_allocator(), type));

+		xml_node n(allocate_node(get_allocator(_root), type));

 		n._root->parent = _root;

 		

 		if (node._root->prev_sibling_c->next_sibling)

@@ -3644,7 +3673,7 @@ namespace pugi
 		if ((this->type() != node_element && this->type() != node_document) || type == node_document || type == node_null) return xml_node();

 		if (node.parent() != *this) return xml_node();

 	

-		xml_node n(allocate_node(get_allocator(), type));

+		xml_node n(allocate_node(get_allocator(_root), type));

 		n._root->parent = _root;

 	

 		if (node._root->next_sibling)

@@ -3708,7 +3737,7 @@ namespace pugi
 		if (a._attr->prev_attribute_c->next_attribute) a._attr->prev_attribute_c->next_attribute = a._attr->next_attribute;

 		else _root->first_attribute = a._attr->next_attribute;

 

-		destroy_attribute(a._attr, get_allocator());

+		destroy_attribute(a._attr, get_allocator(_root));

 	}

 

 	void xml_node::remove_child(const char_t* name)

@@ -3726,7 +3755,7 @@ namespace pugi
 		if (n._root->prev_sibling_c->next_sibling) n._root->prev_sibling_c->next_sibling = n._root->next_sibling;

 		else _root->first_child = n._root->next_sibling;

         

-        destroy_node(n._root, get_allocator());

+        destroy_node(n._root, get_allocator(_root));

 	}

 

 	xml_node xml_node::find_child_by_attribute(const char_t* name, const char_t* attr_name, const char_t* attr_value) const

@@ -4102,10 +4131,6 @@ namespace pugi
 		return temp;

 	}

 

-	xml_memory_page::xml_memory_page(): allocator(0), memory(0), prev(0), next(0), busy_size(0), freed_size(0)

-	{

-	}

-

 	const char* xml_parse_result::description() const

 	{

 		switch (status)

@@ -4141,13 +4166,6 @@ namespace pugi
 	xml_document::~xml_document()

 	{

 		destroy();

-

-		if (_memory.next)

-		{

-			assert(!_memory.next->next);

-

-			xml_allocator::deallocate_page(_memory.next);

-		}

 	}

 

 	void xml_document::create()

@@ -4155,22 +4173,26 @@ namespace pugi
 		destroy();

 

 		// initialize sentinel page

-		_memory.busy_size = xml_memory_page_size;

+		assert(offsetof(xml_memory_page, data) + sizeof(xml_document_struct) + xml_memory_page_alignment <= sizeof(_memory));

 

-		// allocate new root

-		xml_allocator alloc(_memory.next ? _memory.next : &_memory);

-		

-		_root = allocate_document(alloc);

+		// align upwards to page boundary

+		void* page_memory = reinterpret_cast<void*>((reinterpret_cast<uintptr_t>(_memory) + (xml_memory_page_alignment - 1)) & ~(xml_memory_page_alignment - 1));

+

+		// prepare page structure

+		xml_memory_page* page = xml_memory_page::construct(page_memory);

 

+		page->busy_size = xml_memory_page_size;

+

+		// allocate new root

+		_root = new (page->data) xml_document_struct(page);

 		_root->prev_sibling_c = _root;

 

 		// setup allocator

 		xml_allocator& a = static_cast<xml_document_struct*>(_root)->allocator;

-		a = alloc;

+		a = xml_allocator(page);

 

-		// setup page

-		assert(_memory.next);

-		_memory.next->allocator = &a;

+		// setup sentinel page

+		page->allocator = &a;

 	}

 

 	void xml_document::destroy()

@@ -4182,13 +4204,14 @@ namespace pugi
 			_buffer = 0;

 		}

 

-		// destroy dynamic storage, leave sentinel page and next page (if any)

+		// destroy dynamic storage, leave sentinel page (it's in static memory)

 		if (_root)

 		{

-			assert(_memory.next);

+			xml_memory_page* root_page = reinterpret_cast<xml_memory_page*>(_root->header & xml_memory_page_pointer_mask);

+			assert(root_page && !root_page->prev && !root_page->memory);

 

 			// destroy all pages

-			for (xml_memory_page* page = _memory.next->next; page; )

+			for (xml_memory_page* page = root_page->next; page; )

 			{

 				xml_memory_page* next = page->next;

 

@@ -4197,17 +4220,13 @@ namespace pugi
 				page = next;

 			}

 

-			// cleanup next page

-			_memory.next->allocator = 0;

-			_memory.next->next = 0;

-			_memory.next->busy_size = _memory.next->freed_size = 0;

+			// cleanup root page

+			root_page->allocator = 0;

+			root_page->next = 0;

+			root_page->busy_size = root_page->freed_size = 0;

 

 			_root = 0;

 		}

-		else

-		{

-			assert(!_memory.next);

-		}

 	}

 

 #ifndef PUGIXML_NO_STL

diff --git a/src/pugixml.hpp b/src/pugixml.hpp
index 9cdad19..7523079 100644
--- a/src/pugixml.hpp
+++ b/src/pugixml.hpp
@@ -131,13 +131,6 @@ namespace pugi
 	// Parsing options

 

 	/**

-	 * Memory page size, used for fast allocator. Memory for DOM tree is allocated in pages of

-	 * xml_memory_page_size + size of header (approximately 64 bytes)

-	 * This value affects size of xml_memory_page class.

-	 */

-	const size_t xml_memory_page_size = 32768;

-

-	/**

 	 * Minimal parsing mode. Equivalent to turning all other flags off. This set of flags means

 	 * that pugixml does not add pi/cdata sections or comments to DOM tree and does not perform

 	 * any conversions for input data, meaning fastest parsing.

@@ -329,8 +322,6 @@ namespace pugi
 	struct xml_attribute_struct;

 	struct xml_node_struct;

 

-	struct xml_allocator;

-

 	class xml_node_iterator;

 	class xml_attribute_iterator;

 

@@ -787,9 +778,6 @@ namespace pugi
 		/// \internal Initializing ctor

 		explicit xml_node(xml_node_struct* p);

 

-		/// \internal Get allocator

-		xml_allocator& get_allocator() const;

-

 	private:

 		template <typename OutputIterator> void all_elements_by_name_w_helper(const char_t* name, OutputIterator it) const

 		{

@@ -1762,24 +1750,6 @@ namespace pugi
 		virtual bool end(xml_node&);

 	};

 

-	/// \internal Memory page

-	struct PUGIXML_CLASS xml_memory_page

-	{

-		xml_memory_page();

-

-		xml_allocator* allocator;

-

-		void* memory;

-

-		xml_memory_page* prev;

-		xml_memory_page* next;

-

-		size_t busy_size;

-		size_t freed_size;

-

-		char data[1];

-	};

-

 	/**

 	 * Struct used to distinguish parsing with ownership transfer from parsing without it.

 	 * \see xml_document::parse

@@ -1847,7 +1817,7 @@ namespace pugi
 	private:

 		char_t* _buffer;

 

-		xml_memory_page _memory;

+		char _memory[192];

 		

 		xml_document(const xml_document&);

 		const xml_document& operator=(const xml_document&);