Variables Table

Variables Table — A table of variables with optional bound literal values.

Synopsis

typedef             rasqal_variables_table;
rasqal_variables_table * rasqal_new_variables_table     (rasqal_world *world);
void                rasqal_free_variables_table         (rasqal_variables_table *vt);
rasqal_variable *   rasqal_variables_table_add          (rasqal_variables_table *vt,
                                                         rasqal_variable_type type,
                                                         const char *name,
                                                         rasqal_literal *value);
rasqal_variable *   rasqal_variables_table_add2         (rasqal_variables_table *vt,
                                                         rasqal_variable_type type,
                                                         const char *name,
                                                         size_t name_len,
                                                         rasqal_literal *value);
int                 rasqal_variables_table_add_variable (rasqal_variables_table *vt,
                                                         rasqal_variable *variable);
rasqal_variable *   rasqal_variables_table_get_by_name  (rasqal_variables_table *vt,
                                                         rasqal_variable_type type,
                                                         const char *name);
int                 rasqal_variables_table_contains     (rasqal_variables_table *vt,
                                                         rasqal_variable_type type,
                                                         const char *name);

Description

A table of rasqal_variable usually associated with a rasqal_query query or rasqal_query_results query result set. The order of the variables in the table may be significant, such as for a standalone query result set in which case it might define the order of variables in resulting rows.

Details

rasqal_variables_table

typedef struct rasqal_variables_table_s rasqal_variables_table;

Internal - for now

rasqal_new_variables_table ()

rasqal_variables_table * rasqal_new_variables_table     (rasqal_world *world);

Constructor - create a new variables table

`world` :	rasqal world
Returns :	new variables table or NULL On failure

rasqal_free_variables_table ()

void                rasqal_free_variables_table         (rasqal_variables_table *vt);

Destructor - destroy a new variables table

vt :

rasqal variables table

rasqal_variables_table_add ()

rasqal_variable *   rasqal_variables_table_add          (rasqal_variables_table *vt,
                                                         rasqal_variable_type type,
                                                         const char *name,
                                                         rasqal_literal *value);

Constructor - Create a new variable and add it to the variables table

Deprecated: for rasqal_variables_table_add2() which copies the name and value

The name and value become owned by the rasqal_variable structure. If a variable with the name already exists, that is returned and the new value is ignored.

`vt` :	rasqal_variables_table to associate the variable with
`type` :	variable type defined by enumeration rasqal_variable_type
`name` :	variable name
`value` :	variable rasqal_literal value (or NULL)
Returns :	a new rasqal_variable or NULL on failure.

rasqal_variables_table_add2 ()

rasqal_variable *   rasqal_variables_table_add2         (rasqal_variables_table *vt,
                                                         rasqal_variable_type type,
                                                         const char *name,
                                                         size_t name_len,
                                                         rasqal_literal *value);

Constructor - Create a new variable and add it to the variables table

The name and value fields are copied. If a variable with the name already exists, that is returned and the new value is ignored.

`vt` :	rasqal_variables_table to associate the variable with
`type` :	variable type defined by enumeration rasqal_variable_type
`name` :	variable name
`name_len` :	length of `name` (or 0)
`value` :	variable rasqal_literal value (or NULL)
Returns :	a new rasqal_variable or NULL on failure.

rasqal_variables_table_add_variable ()

int                 rasqal_variables_table_add_variable (rasqal_variables_table *vt,
                                                         rasqal_variable *variable);

Constructor - Add an existing variable to the variables table

The variables table vt takes a reference to variable. This function will fail if the variable is already in the table. Use rasqal_variables_table_contains() to check before calling.

`vt` :	rasqal_variables_table to associate the variable with
`variable` :	existing variable to add
Returns :	non-0 on failure (such as name already exists)

rasqal_variables_table_get_by_name ()

rasqal_variable *   rasqal_variables_table_get_by_name  (rasqal_variables_table *vt,
                                                         rasqal_variable_type type,
                                                         const char *name);

Lookup a variable by type and name in the variables table.

Note that looking up for any type RASQAL_VARIABLE_TYPE_UNKNOWN may a name match but for any type so in cases where the query has both a named and anonymous (extensional) variable, an arbitrary one will be returned.

`vt` :	the variables table
`type` :	the variable type to match or RASQAL_VARIABLE_TYPE_UNKNOWN for any.
`name` :	the variable type
Returns :	a shared pointer to the rasqal_variable or NULL if not found

rasqal_variables_table_contains ()

int                 rasqal_variables_table_contains     (rasqal_variables_table *vt,
                                                         rasqal_variable_type type,
                                                         const char *name);

Check if there is a variable with the given type and name in the variables table

`vt` :	rasqal_variables_table to lookup
`type` :	variable type
`name` :	variable name
Returns :	non-0 if the variable is present

			Rasqal RDF Query Library Manual
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