copy_on_write< T, A > Class Template Reference [ABI-Safe Utilities]

A copy-on-write wrapper for any model of Regular. More...

#include <copy_on_write.hpp>

List of all members.

Public Types
typedef A	allocator_type
typedef T	value_type
Public Member Functions
	copy_on_write ()
	copy_on_write (const allocator_type &a)
	copy_on_write (const copy_on_write &x)
	copy_on_write (move_from< copy_on_write > x)
	copy_on_write (T x)
allocator_type	get_allocator () const
bool	identity (const copy_on_write &x) const
	operator const value_type & () const
const value_type &	operator* () const
const value_type *	operator-> () const
copy_on_write &	operator= (T x)
copy_on_write &	operator= (copy_on_write x)
const value_type &	read () const
bool	unique_instance () const
value_type &	write ()
	~copy_on_write ()
Friends
bool	operator!= (const copy_on_write &x, const copy_on_write &y)
bool	operator< (const copy_on_write &x, const copy_on_write &y)
bool	operator<= (const copy_on_write &x, const copy_on_write &y)
bool	operator== (const copy_on_write &x, const copy_on_write &y)
bool	operator> (const copy_on_write &x, const copy_on_write &y)
bool	operator>= (const copy_on_write &x, const copy_on_write &y)
void	swap (copy_on_write &x, copy_on_write &y)

---

Detailed Description

template<typename T, typename A = adobe::capture_allocator<T>>
class adobe::version_1::copy_on_write< T, A >

Model Of:

• Movable

Requirements:

• T models Regular (supports T models Movable).

Copy-on-write sematics allow for object to be lazily copied - only creating a copy when the value is modified and there is more than one reference to the value.

Note:

copy_on_write is thread safe when complier with BOOST_HAS_THREADS defined.

To get an instance with a particular allocator one would have to write:

copy_on_write<T> x(custom_allocator);
x.write() = value;

Definition at line 71 of file copy_on_write.hpp.

---

Member Typedef Documentation

typedef A allocator_type

The type of allocator.

Definition at line 77 of file copy_on_write.hpp.

typedef T value_type

The type of value stored.

Definition at line 75 of file copy_on_write.hpp.

---

Constructor & Destructor Documentation

copy_on_write

(

)

The first call to the default constructor will construct a default instance of value_type which will be used for subsequent calls to the default constructor. The default instance will be released at exit.

Definition at line 91 of file copy_on_write.hpp.

copy_on_write

(

const allocator_type &

a )

[explicit]

Initializes the instance with a custom allocator

Definition at line 101 of file copy_on_write.hpp.

copy_on_write

(

T

x )

Constructs a new copy_on_write object with a value x.

Parameters:

x	A default value to assign to this object

Note:

This constructor is for value types which do not support the move library.

Definition at line 116 of file copy_on_write.hpp.

copy_on_write

(

const copy_on_write< T, A > &

x )

Copy construction is a non-throwing operation and simply increments the reference count on the stored object.

Definition at line 124 of file copy_on_write.hpp.

copy_on_write

(

move_from< copy_on_write< T, A > >

x )

Definition at line 131 of file copy_on_write.hpp.

~copy_on_write

(

)

Definition at line 137 of file copy_on_write.hpp.

---

Member Function Documentation

allocator_type get_allocator

(

)

const

Definition at line 271 of file copy_on_write.hpp.

bool identity

(

const copy_on_write< T, A > &

x )

const

identity is used to see if two copy_on_write items refer to the same instance.

Returns:

Boolean; true if the underlying object instance is shared by both objects.

Definition at line 247 of file copy_on_write.hpp.

operator const value_type &

(

)

const

Obtain a const reference to the underlying object.

Returns:

A const reference to the underlying object

Definition at line 201 of file copy_on_write.hpp.

const value_type& operator*

(

)

const

Obtain a const reference to the underlying object.

This is provided because you cannot override operator.(). It allows copy_on_write to be used with common transformation techniques, such as boost indirect_iterator and transform_iterator. It does not imply "pointer" semantics.

Returns:

A const reference to the underlying object

Definition at line 214 of file copy_on_write.hpp.

const value_type* operator->

(

)

const

Obtain a const pointer to the underlying object.

This is provided because you cannot override operator.(). It allows copy_on_write to be used with common transformation techniques, such as boost indirect_iterator and transform_iterator. It does not imply "pointer" semantics.

Returns:

A const pointer to the underlying object

Definition at line 227 of file copy_on_write.hpp.

copy_on_write& operator=

(

copy_on_write< T, A >

x )

As with copy construction, assignment is a non-throwing operation which releases the old value and increments the reference count of the item being assigned to.

Definition at line 147 of file copy_on_write.hpp.

copy_on_write& operator=

(

T

x )

Definition at line 151 of file copy_on_write.hpp.

const value_type& read

(

)

const

Obtain a const reference to the underlying object.

Returns:

A const reference to the underlying object

Definition at line 190 of file copy_on_write.hpp.

bool unique_instance

(

)

const

unique_instance returns whether or not the reference count to the object instance is one. This is useful to determine if writing will cause a copy.

Returns:

true if the ref count for the instance is one.

Definition at line 237 of file copy_on_write.hpp.

value_type& write

(

)

Obtain a reference to the value the object is referencing. This will copy the underlying value (if necessary) so changes to the value do not affect other copy_on_write objects.

Note that write() does not have the same preconditions as operator=(). write() returns a reference to the underlying object's value, thus requiring that an underlying object exist. operator=() on the other hand will perform an allocation if one is necessary.

Returns:

A reference to the underlying object

Definition at line 175 of file copy_on_write.hpp.

---

Friends And Related Function Documentation

bool operator!=	(	const copy_on_write< T, A > &	x,
		const copy_on_write< T, A > &	y
	)		[friend]

Definition at line 268 of file copy_on_write.hpp.

bool operator<	(	const copy_on_write< T, A > &	x,
		const copy_on_write< T, A > &	y
	)		[friend]

Definition at line 253 of file copy_on_write.hpp.

bool operator<=	(	const copy_on_write< T, A > &	x,
		const copy_on_write< T, A > &	y
	)		[friend]

Definition at line 259 of file copy_on_write.hpp.

bool operator==	(	const copy_on_write< T, A > &	x,
		const copy_on_write< T, A > &	y
	)		[friend]

Definition at line 265 of file copy_on_write.hpp.

bool operator>	(	const copy_on_write< T, A > &	x,
		const copy_on_write< T, A > &	y
	)		[friend]

Definition at line 256 of file copy_on_write.hpp.

bool operator>=	(	const copy_on_write< T, A > &	x,
		const copy_on_write< T, A > &	y
	)		[friend]

Definition at line 262 of file copy_on_write.hpp.

void swap	(	copy_on_write< T, A > &	x,
		copy_on_write< T, A > &	y
	)		[friend]

Definition at line 250 of file copy_on_write.hpp.