rapidxml::memory_pool Class Reference

This class is used by the parser to create new nodes and attributes, without overheads of dynamic memory allocation. More...

#include <rapidxml.h>

Inheritance diagram for rapidxml::memory_pool:

Public Member Functions
	memory_pool ()
	Constructs empty pool with default allocator functions. More...
	~memory_pool ()
	Destroys pool and frees all the memory. More...
xml_node *	allocate_node (node_type type, const char *name=nullptr, const char *value=nullptr, std::size_t name_size=0, std::size_t value_size=0)
	Allocates a new node from the pool, and optionally assigns name and value to it. More...
xml_attribute *	allocate_attribute (const char *name=nullptr, const char *value=nullptr, std::size_t name_size=0, std::size_t value_size=0)
	Allocates a new attribute from the pool, and optionally assigns name and value to it. More...
char *	allocate_string (const char *source=nullptr, std::size_t size=0)
	Allocates a char array of given size from the pool, and optionally copies a given string to it. More...
xml_node *	clone_node (const xml_node *source, xml_node *result=nullptr)
	Clones an xml_node and its hierarchy of child nodes and attributes. More...
void	clear ()
	Clears the pool. More...
void	set_allocator (alloc_func *af, free_func *ff)
	Sets or resets the user-defined memory allocation functions for the pool. More...

Detailed Description

This class is used by the parser to create new nodes and attributes, without overheads of dynamic memory allocation.

In most cases, you will not need to use this class directly. However, if you need to create nodes manually or modify names/values of nodes, you are encouraged to use memory_pool of relevant xml_document to allocate the memory. Not only is this faster than allocating them by using new operator, but also their lifetime will be tied to the lifetime of document, possibly simplyfing memory management.

Call allocate_node() or allocate_attribute() functions to obtain new nodes or attributes from the pool. You can also call allocate_string() function to allocate strings. Such strings can then be used as names or values of nodes without worrying about their lifetime. Note that there is no free() function – all allocations are freed at once when clear() function is called, or when the pool is destroyed.

It is also possible to create a standalone memory_pool, and use it to allocate nodes, whose lifetime will not be tied to any document.

Pool maintains RAPIDXML_STATIC_POOL_SIZE bytes of statically allocated memory. Until static memory is exhausted, no dynamic memory allocations are done. When static memory is exhausted, pool allocates additional blocks of memory of size RAPIDXML_DYNAMIC_POOL_SIZE each, by using global new[] and delete[] operators. This behaviour can be changed by setting custom allocation routines. Use set_allocator() function to set them.

Allocations for nodes, attributes and strings are aligned at RAPIDXML_ALIGNMENT bytes. This value defaults to the size of pointer on target architecture.

To obtain absolutely top performance from the parser, it is important that all nodes are allocated from a single, contiguous block of memory. Otherwise, cache misses when jumping between two (or more) disjoint blocks of memory can slow down parsing quite considerably. If required, you can tweak RAPIDXML_STATIC_POOL_SIZE, RAPIDXML_DYNAMIC_POOL_SIZE and RAPIDXML_ALIGNMENT to obtain best wasted memory to performance compromise. To do it, define their values before rapidxml.hpp file is included.

Parameters

Ch	Character type of created nodes.

Constructor & Destructor Documentation

memory_pool()

rapidxml::memory_pool::memory_pool

(

)

Constructs empty pool with default allocator functions.

~memory_pool()

rapidxml::memory_pool::~memory_pool

(

)

Destroys pool and frees all the memory.

This causes memory occupied by nodes allocated by the pool to be freed. Nodes allocated from the pool are no longer valid.

Member Function Documentation

allocate_attribute()

xml_attribute * rapidxml::memory_pool::allocate_attribute	(	const char *	name = nullptr,
		const char *	value = nullptr,
		std::size_t	name_size = 0,
		std::size_t	value_size = 0
	)

Allocates a new attribute from the pool, and optionally assigns name and value to it.

If the allocation request cannot be accomodated, this function will throw std::bad_alloc. If exceptions are disabled by defining RAPIDXML_NO_EXCEPTIONS, this function will call rapidxml::parse_error_handler() function.

Parameters

name	Name to assign to the attribute, or 0 to assign no name.
value	Value to assign to the attribute, or 0 to assign no value.
name_size	Size of name to assign, or 0 to automatically calculate size from name string.
value_size	Size of value to assign, or 0 to automatically calculate size from value string.

Returns

Pointer to allocated attribute. This pointer will never be NULL.

allocate_node()

xml_node * rapidxml::memory_pool::allocate_node	(	node_type	type,
		const char *	name = nullptr,
		const char *	value = nullptr,
		std::size_t	name_size = 0,
		std::size_t	value_size = 0
	)

Allocates a new node from the pool, and optionally assigns name and value to it.

If the allocation request cannot be accomodated, this function will throw std::bad_alloc. If exceptions are disabled by defining RAPIDXML_NO_EXCEPTIONS, this function will call rapidxml::parse_error_handler() function.

Parameters

type	Type of node to create.
name	Name to assign to the node, or 0 to assign no name.
value	Value to assign to the node, or 0 to assign no value.
name_size	Size of name to assign, or 0 to automatically calculate size from name string.
value_size	Size of value to assign, or 0 to automatically calculate size from value string.

Returns

Pointer to allocated node. This pointer will never be NULL.

allocate_string()

char * rapidxml::memory_pool::allocate_string	(	const char *	source = nullptr,
		std::size_t	size = 0
	)

Allocates a char array of given size from the pool, and optionally copies a given string to it.

If the allocation request cannot be accomodated, this function will throw std::bad_alloc. If exceptions are disabled by defining RAPIDXML_NO_EXCEPTIONS, this function will call rapidxml::parse_error_handler() function.

Parameters

source	String to initialize the allocated memory with, or 0 to not initialize it.
size	Number of characters to allocate, or zero to calculate it automatically from source string length; if size is 0, source string must be specified and null terminated.

Returns

Pointer to allocated char array. This pointer will never be NULL.

clear()

void rapidxml::memory_pool::clear

(

)

Clears the pool.

This causes memory occupied by nodes allocated by the pool to be freed. Any nodes or strings allocated from the pool will no longer be valid.

clone_node()

xml_node * rapidxml::memory_pool::clone_node	(	const xml_node *	source,
		xml_node *	result = nullptr
	)

Clones an xml_node and its hierarchy of child nodes and attributes.

Nodes and attributes are allocated from this memory pool. Names and values are not cloned, they are shared between the clone and the source. Result node can be optionally specified as a second parameter, in which case its contents will be replaced with cloned source node. This is useful when you want to clone entire document.

Parameters

source	Node to clone.
result	Node to put results in, or 0 to automatically allocate result node

Returns

Pointer to cloned node. This pointer will never be NULL.

set_allocator()

void rapidxml::memory_pool::set_allocator	(	alloc_func *	af,
		free_func *	ff
	)

Sets or resets the user-defined memory allocation functions for the pool.

This can only be called when no memory is allocated from the pool yet, otherwise results are undefined. Allocation function must not return invalid pointer on failure. It should either throw, stop the program, or use longjmp() function to pass control to other place of program. If it returns invalid pointer, results are undefined.

User defined allocation functions must have the following forms:

void *allocate(std::size_t size);
void free(void *pointer);

Parameters

af	Allocation function, or 0 to restore default function
ff	Free function, or 0 to restore default function

---

The documentation for this class was generated from the following files:

• Encoding/RapidXml/rapidxml.h
• Encoding/RapidXml/rapidxml.cpp