This group discusses the functions that allow you to store a single copy of a string, and use it in multiple places throughout your program.

This is a method to reduce the number of duplicated strings kept in the memory. It's pretty common for the same strings to be dynamically allocated repeatedly between applications and libraries, especially in circumstances where you could have multiple copies of a structure that allocates the string. So rather than duplicating and freeing these strings, you request a read-only pointer to an existing string and only incur the overhead of a hash lookup.

It sounds like micro-optimizing, but profiling has shown that this can have a significant impact as you scale the number of copies up. It improves the string creation/destruction speed, reduces memory use, and decreases memory fragmentation, so a win all-around.

Remarks:

Using eina stringshares usually boils down to:

 const char *str = eina_stringshare_add("My string");
 ...
 //Use str
 ...
 eina_stringshare_del(str);

It's very important to note that string shares are const, changing them results in an undefined behavior. eina_stringshare_del() doesn't guarantee that the string share is freed, it releases a reference to it, but if other references to it still exist the string share lives until those are released.

The following diagram gives an idea of what happens as you create strings with eina_stringshare_add():

Functions
Eina_Stringshare *	eina_stringshare_add_length (const char *str, unsigned int slen)
	Retrieves an instance of a string for use in a program.
Eina_Stringshare *	eina_stringshare_add (const char *str)
	Retrieves an instance of a string for use in a program.
Eina_Stringshare *	eina_stringshare_printf (const char *fmt,...)
	Retrieves an instance of a string for use in a program from a format string.
Eina_Stringshare *	eina_stringshare_vprintf (const char *fmt, va_list args)
	Retrieves an instance of a string for use in a program from a format string.
Eina_Stringshare *	eina_stringshare_nprintf (unsigned int len, const char *fmt,...)
	Retrieves an instance of a string for use in a program from a format string with size limitation.
Eina_Stringshare *	eina_stringshare_ref (Eina_Stringshare *str)
	Increments references of the given shared string.
void	eina_stringshare_del (Eina_Stringshare *str)
	Notes that the given string has lost an instance.
int	eina_stringshare_strlen (Eina_Stringshare *str)
	Notes that the given string must be shared.
void	eina_stringshare_dump (void)
	Dumps the contents of share_common.
static Eina_Bool	eina_stringshare_refplace (Eina_Stringshare *p_str, Eina_Stringshare news)
	Replace the previously stringshared pointer with another stringshared pointer.
static Eina_Bool	eina_stringshare_replace (Eina_Stringshare *p_str, const char news)
	Replace the previously stringshared pointer with new content.
static Eina_Bool	eina_stringshare_replace_length (Eina_Stringshare *p_str, const char news, unsigned int slen)
	Replace the previously stringshared pointer with a new content.
Typedefs
typedef const char	Eina_Stringshare
	Interchangeable with "const char *", but still a good visual hint for the purpose. Maybe in the future we may even add strict type checking.

Typedef Documentation

Eina_Stringshare

Interchangeable with "const char *", but still a good visual hint for the purpose. Maybe in the future we may even add strict type checking.

Since (EFL) :: 1.2.0

Function Documentation

Eina_Stringshare* eina_stringshare_add ( const char * str )

Retrieves an instance of a string for use in a program.

This function retrieves an instance of str. If str is NULL, then NULL is returned. If str is already stored, it is just returned and its reference counter is increased. Otherwise a duplicated string of str is returned.

Since :: 2.3.1

Remarks:: The string str must be NULL terminated ('\0') and its full length should be used. To use a part of the string or non-null terminated, use eina_stringshare_add_length() instead.

Parameters:

[in] str The NULL-terminated string to retrieve an instance of

Returns:: A pointer to an instance of the string on success, otherwise NULL on failure

See also:: eina_stringshare_add_length()

Eina_Stringshare* eina_stringshare_add_length	(	const char *	str,
		unsigned int	slen
	)

Retrieves an instance of a string for use in a program.

This function retrieves an instance of str. If str is NULL, then NULL is returned. If str is already stored, it is just returned and its reference counter is increased. Otherwise a duplicated string of str is returned.

Since :: 2.3.1

Remarks:: This function does not check the string size, but uses the exact given size. This can be used to share_common parts of a larger buffer or substring.

Parameters:

[in]	str	The string to retrieve an instance of
[in]	slen	The string size (<= strlen(str))

Returns:: A pointer to an instance of the string on success, otherwise NULL on failure

See also:: eina_share_common_add()

void eina_stringshare_del ( Eina_Stringshare * str )

Notes that the given string has lost an instance.

This function decreases the reference counter associated to str if it exists. If that counter reaches 0, the memory associated to str is freed. If str is NULL, the function returns immediately.

Since :: 2.3.1

Remarks:: If the given pointer is not shared, bad things happen, mostly a segmentation fault.

Parameters:

[in] str string The given string

void eina_stringshare_dump ( void )

Dumps the contents of share_common.

This function dumps all the strings from share_common to stdout with a DDD: prefix per line and a memory usage summary.

Since :: 2.3.1

Eina_Stringshare* eina_stringshare_nprintf	(	unsigned int	len,
		const char *	fmt,
			...
	)

Retrieves an instance of a string for use in a program from a format string with size limitation.

This function retrieves an instance of fmt limited by len. If fmt is NULL or len is < 1, then NULL is returned. If the resulting string is already stored, it is just returned and its reference counter is increased. Otherwise a duplicated string is returned.

len length of the format string is used. To use the entire format string, use eina_stringshare_printf() instead.

Since :: 2.3.1

Parameters:

[in]	len	The length of the format string to use
[in]	fmt	The format string to retrieve an instance of

Returns:: A pointer to an instance of the string on success, otherwise NULL on failure

See also:: eina_stringshare_printf()

Eina_Stringshare* eina_stringshare_printf	(	const char *	fmt,
			...
	)

Retrieves an instance of a string for use in a program from a format string.

This function retrieves an instance of fmt. If fmt is NULL, then NULL is returned. If fmt is already stored, it is just returned and its reference counter is increased. Otherwise a duplicated string is returned.

The format string fmt must be NULL-terminated ('\0') and its full length should be used. To use a part of the format string or non-null terminated, use eina_stringshare_nprintf() instead.

Since :: 2.3.1

Parameters:

[in] fmt The NULL-terminated format string to retrieve an instance of

Returns:: A pointer to an instance of the string on success, otherwise NULL on failure

See also:: eina_stringshare_nprintf()

Eina_Stringshare* eina_stringshare_ref ( Eina_Stringshare * str )

Increments references of the given shared string.

Since :: 2.3.1

Remarks:: This is similar to eina_share_common_add(), but it's faster since it avoids lookups if possible, but on the down side it requires the parameter to be a shared string. In other words, it must be the return of a previous call to one of the stringshare functions.; There is no unref since this is the work of eina_share_common_del().

Parameters:

[in] str The shared string

Returns:: A pointer to an instance of the string on success, otherwise NULL on failure

static Eina_Bool eina_stringshare_refplace	(	Eina_Stringshare **	p_str,
		Eina_Stringshare *	news
	)		`[static]`

Replace the previously stringshared pointer with another stringshared pointer.

The string pointed by p_str must be previously stringshared or NULL and it will be eina_stringshare_del(). The new string must also be stringshared and will be passed to eina_stringshare_ref() and then assigned to *p_str. This function is identical to eina_stringshare_replace() except that it calls eina_stringshare_ref() instead of eina_stringshare_add()

Since :: 2.3.1

Parameters:

[out]	p_str	pointer to the stringhare to be replaced. Must not be `NULL`, but `*p_str` may be `NULL` as it is a valid stringshare handle.
[out]	news	new string to replace with, may be `NULL`.

Returns:: EINA_TRUE if the strings were different and thus replaced, EINA_FALSE if the strings were the same after shared.

static Eina_Bool eina_stringshare_replace	(	Eina_Stringshare **	p_str,
		const char *	news
	)		`[static]`

Replace the previously stringshared pointer with new content.

The string pointed by p_str must be previously stringshared or NULL and it will be eina_stringshare_del(). The new string will be passed to eina_stringshare_add() and then assigned to *p_str.

Since :: 2.3.1

Parameters:

[in]	p_str	pointer to the stringhare to be replaced. Must not be `NULL`, but `*p_str` may be `NULL` as it is a valid stringshare handle.
[in]	news	new string to be stringshared, may be `NULL`.

Returns:: EINA_TRUE if the strings were different and thus replaced, EINA_FALSE if the strings were the same after shared.

static Eina_Bool eina_stringshare_replace_length	(	Eina_Stringshare **	p_str,
		const char *	news,
		unsigned int	slen
	)		`[static]`

Replace the previously stringshared pointer with a new content.

The string pointed by p_str must be previously stringshared or NULL and it will be eina_stringshare_del(). The new string will be passed to eina_stringshare_add_length() and then assigned to *p_str.

Since :: 2.3.1

Parameters:

[in]	p_str	pointer to the stringhare to be replaced. Must not be `NULL`, but `*p_str` may be `NULL` as it is a valid stringshare handle.
[in]	news	new string to be stringshared, may be `NULL`.
[in]	slen	The string size (<= strlen(str)).

Returns:: EINA_TRUE if the strings were different and thus replaced, EINA_FALSE if the strings were the same after shared.

int eina_stringshare_strlen ( Eina_Stringshare * str )

Notes that the given string must be shared.

This function is a cheap way to known the length of a shared string.

Since :: 2.3.1

Remarks:: If the given pointer is not shared, bad things happen, mostly a segmentation fault. If in doubt, try strlen().

Parameters:

[in] str The shared string to know the length of
It is safe to give NULL, in which case 0 is returned.

Returns:: The length of a shared string

Eina_Stringshare* eina_stringshare_vprintf	(	const char *	fmt,
		va_list	args
	)

Retrieves an instance of a string for use in a program from a format string.

This function retrieves an instance of fmt with args. If fmt is NULL, then NULL is returned. If fmt with args is already stored, it is just returned and its reference counter is increased. Otherwise a duplicated string is returned.

The format string fmt must be NULL-terminated ('\0') and its full length should be used. To use a part of the format string or non-null terminated, use eina_stringshare_nprintf() instead.

Since :: 2.3.1

Parameters:

[in]	fmt	The NULL-terminated format string to retrieve an instance of
[in]	args	The va_args for fmt

Returns:: A pointer to an instance of the string on success, otherwise NULL on failure

See also:: eina_stringshare_nprintf()

Functions

Typedefs

Typedef Documentation

Function Documentation