Variables

Variables — Variable with names and literal value.

Description

A class to hold a variable with optional name and a rasqal_literal value. The name is not required for SPARQL anonymous variables.

Details

rasqal_variable

typedef struct {
  rasqal_variables_table* vars_table;
  const char * name;
  rasqal_literal* value;
  int offset;
  rasqal_variable_type type;
  struct rasqal_expression_s* expression;
  void *user_data;
  int usage;
} rasqal_variable;

Binding between a variable name and a value.

Includes internal field offset for recording the offset into the (internal) rasqal_query variables array.

rasqal_variables_table *vars_table;

variables table that owns this variable

const char *name;

Variable name.

rasqal_literal *value;

Variable value or NULL if unbound.

int offset;

Internal.

rasqal_variable_type type;

Variable type.

struct rasqal_expression_s *expression;

Expression when the variable is a computed SELECT expression

void *user_data;

Pointer to user data associated with a variable. This is not used by rasqal.

int usage;

reference count

rasqal_new_variable_from_variable ()

rasqal_variable *   rasqal_new_variable_from_variable   (rasqal_variable *v);

Copy Constructor - Create a new Rasqal variable from an existing one

This adds a new reference to the variable, it does not do a deep copy

v :

rasqal_variable to copy

Returns :

a new rasqal_variable or NULL on failure.

rasqal_free_variable ()

void                rasqal_free_variable                (rasqal_variable *v);

Destructor - Destroy a Rasqal variable object.

v :

rasqal_variable object

rasqal_variable_print ()

int                 rasqal_variable_print               (rasqal_variable *v,
                                                         FILE *fh);

Print a Rasqal variable in a debug format.

The print debug format may change in any release.

v :

the rasqal_variable object

fh :

the FILE* handle to print to

Returns :

non-0 on failure

rasqal_variable_set_value ()

void                rasqal_variable_set_value           (rasqal_variable *v,
                                                         rasqal_literal *l);

Set the value of a Rasqal variable.

The variable value is an input parameter and is copied in, not shared. If the variable value is NULL, any existing value is deleted.

v :

the rasqal_variable object

l :

the rasqal_literal value to set (or NULL)

enum rasqal_variable_type

typedef enum {
  RASQAL_VARIABLE_TYPE_UNKNOWN   = 0,
  RASQAL_VARIABLE_TYPE_NORMAL    = 1,
  RASQAL_VARIABLE_TYPE_ANONYMOUS = 2
} rasqal_variable_type;

Rasqal variable types.

ANONYMOUS can be used in queries but cannot be returned in a result.

RASQAL_VARIABLE_TYPE_UNKNOWN

Internal.

RASQAL_VARIABLE_TYPE_NORMAL

The regular variable type.

RASQAL_VARIABLE_TYPE_ANONYMOUS

Anonymous variable type.


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