These functions provide some helper for a pseudo Copy On Write mechanism.

Eina_Cow will return const memory pointer to some default value that you will be able to change only by requesting a writable pointer. Later on a garbage collector can come online and try to merge back some of those pointer.

Since (EFL) :: 1.8.0

Functions
Eina_Cow *	eina_cow_add (const char name, unsigned int struct_size, unsigned int step, const void default_value, Eina_Bool gc)
	Instantiates a new Eina_Cow pool.
void	eina_cow_del (Eina_Cow *cow)
	Destroys an Eina_Cow pool and all the allocated memory.
const Eina_Cow_Data *	eina_cow_alloc (Eina_Cow *cow)
	Returns an initialized pointer from the pool.
void	eina_cow_free (Eina_Cow cow, const Eina_Cow_Data *data)
	Frees a pointer from the pool.
void *	eina_cow_write (Eina_Cow cow, const Eina_Cow_Data const *src)
	Gets a writeable pointer from a const pointer.
void	eina_cow_done (Eina_Cow cow, const Eina_Cow_Data const dst, const void data, Eina_Bool needed_gc)
	Sets back a pointer into read only.
void	eina_cow_memcpy (Eina_Cow cow, const Eina_Cow_Data const dst, const Eina_Cow_Data src)
	Makes the destination contain the same thing as the source pointer.
Eina_Bool	eina_cow_gc (Eina_Cow *cow)
	Tries to find entries that have the same content and update them.
Typedefs
typedef struct _Eina_Cow	Eina_Cow
typedef void	Eina_Cow_Data
Defines
#define	EINA_COW_WRITE_BEGIN(Cow, Read, Write_Type, Write)
	Definition for the macro to setup a writeable pointer from a const one.
#define	EINA_COW_WRITE_END(Cow, Read, Write)
	Definition for the macro to close the writeable pointer.

Define Documentation

#define EINA_COW_WRITE_BEGIN	(	Cow,
		Read,
		Write_Type,
		Write
	)

Value:

do                                  \
    {                                   \
      Write_Type *Write;                        \
                                        \
      Write = eina_cow_write(Cow, ((const Eina_Cow_Data**)&(Read)));

Definition for the macro to setup a writeable pointer from a const one.

Parameters:

Cow	The Eina_Cow where the const pointer come from.
Read	The const pointer to get a writable handler from.
Write_Type	The type of the pointer you want to write to.
Write	The name of the variable where to put the writeable pointer to.

Since (EFL) :: 1.8.0

Be careful this macro opens a C scope that is expected to be closed by EINA_COW_WRITE_END().

#define EINA_COW_WRITE_END	(	Cow,
		Read,
		Write
	)

Value:

eina_cow_done(Cow, ((const Eina_Cow_Data**)&(Read)), Write, \
            EINA_TRUE);                     \
    }                                   \
  while (0);

Definition for the macro to close the writeable pointer.

Parameters:

Cow	The Eina_Cow where the const pointer come from.
Read	The const pointer to get a writable handler from.
Write	The name of the variable where to put the writeable pointer to.

Since (EFL) :: 1.8.0

Be careful this macro close the scope opened by EINA_COW_WRITE_BEGIN().

Typedef Documentation

Eina_Cow

Type for Eina_Cow pool

Eina_Cow_Data

Type of the returned pointer to simplify some reading.

Function Documentation

Eina_Cow* eina_cow_add	(	const char *	name,
		unsigned int	struct_size,
		unsigned int	step,
		const void *	default_value,
		Eina_Bool	gc
	)

Instantiates a new Eina_Cow pool.

Parameters:

name	The name of this pool, used for debug.
struct_size	The size of the object from this pool.
step	How many objects to allocate when the pool gets empty.
default_value	The default value returned by this pool.
gc	Is it possible to run garbage collection on this pool.

Returns:: A valid new Eina_Cow, or NULL on error.

Since :: 3.0

const Eina_Cow_Data* eina_cow_alloc ( Eina_Cow * cow )

Returns an initialized pointer from the pool.

Parameters:

cow	The pool to take things from.

Returns:: A pointer to the new pool instance

Since :: 3.0

void eina_cow_del ( Eina_Cow * cow )

Destroys an Eina_Cow pool and all the allocated memory.

Parameters:

cow	The pool to destroy

Since :: 3.0

void eina_cow_done	(	Eina_Cow *	cow,
		const Eina_Cow_Data const	dst,
		const void *	data,
		Eina_Bool	needed_gc
	)

Sets back a pointer into read only.

Parameters:

cow	The pool the pointer come from.
dst	The read only version of the pointer.
data	The pointer to which data was written to.
needed_gc	Does this pool need to be garbage collected?

NOTE: this function is not thread safe, be careful.

Since :: 3.0

void eina_cow_free	(	Eina_Cow *	cow,
		const Eina_Cow_Data **	data
	)

Frees a pointer from the pool.

Parameters:

cow	The pool to gave back memory to.
data	The data to give back.

Note:: To simplify the caller code *data will point to the default read only state after the call to this function.

Since :: 3.0

Eina_Bool eina_cow_gc ( Eina_Cow * cow )

Tries to find entries that have the same content and update them.

Parameters:

cow	The cow to try to compact.

Returns:: EINA_TRUE if something was compacted, EINA_FALSE if nothing was.

There is no guaranty in the time it will require, but should remain low. It does run a hash function on all possible common structures trying to find the one that match and merge them into one pointer.

Since :: 3.0

void eina_cow_memcpy	(	Eina_Cow *	cow,
		const Eina_Cow_Data const	dst,
		const Eina_Cow_Data *	src
	)

Makes the destination contain the same thing as the source pointer.

Parameters:

cow	The pool the pointers come from.
dst	The destination to update.
src	The source of information to copy.

Since :: 3.0

void* eina_cow_write	(	Eina_Cow *	cow,
		const Eina_Cow_Data const	src
	)

Gets a writeable pointer from a const pointer.

Parameters:

cow	The pool the pointer come from.
src	The pointer you want to write to.

NOTE: this function is not thread safe, be careful.

Since :: 3.0

Functions

Typedefs

Defines

Define Documentation

Typedef Documentation

Function Documentation