value

value — Simplified interface to GValue types used in libuser entities.

Synopsis

#include <libuser/user.h>

#define             LU_VALUE_INVALID_ID
char *              lu_value_strdup                     (const GValue *value);
gboolean            lu_value_init_set_attr_from_string  (GValue *value,
                                                         const char *attr,
                                                         const char *string,
                                                         struct lu_error **error);
void                lu_value_init_set_id                (GValue *value,
                                                         id_t id);
id_t                lu_value_get_id                     (const GValue *value);
int                 lu_values_equal                     (const GValue *a,
                                                         const GValue *b);

Description

Libuser entities store attribute values as GValue, which allows representing any possible data type. Only a few types are needed in practice; the only types applications should hard-code are G_TYPE_LONG and G_TYPE_STRING (G_TYPE_STRING can usually be used as a fallback for other number types).

The only currently used data types that are not conveniently supported using the above types are uid_t and gid_t (which can be together represented in id_t), because they can support values outside of the range of glong. Helper functions are provided to convert values between id_t and GValue, even if the value is stored using G_TYPE_STRING. The GValue types used for storing id_t values are an internal implementation detail of libuser and applications should not rely on them.

Values of each attribute are expected to have a specific type, documented in the documentation of the specific attribute name. Using other types (e.g. using G_TYPE_STRING for LU_UIDNUMBER) is not allowed and results in undefined behavior. You can use lu_value_strdup() and lu_value_init_set_attr_from_string() for conversion between strings and values appropriate for a specific attribute.

Details

LU_VALUE_INVALID_ID

#define LU_VALUE_INVALID_ID ((id_t)-1)

An id_t value that matches no valid user or group ID.

lu_value_strdup ()

char *              lu_value_strdup                     (const GValue *value);

Converts value, of any type used by libuser, to a string. Preferable to hard-coding checks for expected value types.

value :

 GValue

Returns :

 string, should be freed by g_free()

lu_value_init_set_attr_from_string ()

gboolean            lu_value_init_set_attr_from_string  (GValue *value,
                                                         const char *attr,
                                                         const char *string,
                                                         struct lu_error **error);

Initializes a zero-filled (uninitialized) value for storing a value of attribute attr and sets it to the contents of string. To see whether a specific type is used for an attribute, see the documentation of that attribute.

The error messages returned from this function don't contain the input string, to allow the caller to output at least partially usable error message without disclosing the invalid string in e.g. /etc/shadow, which might be somebody's misplaced password.

value :

 GValue

attr :

 Attribute name

string :

 The string to convert

error :

 Filled with a lu_error if an error occurs, or NULL if attr is unknown

Returns :

 TRUE on success, FALSE on error or if attr is unknown

lu_value_init_set_id ()

void                lu_value_init_set_id                (GValue *value,
                                                         id_t id);

Initializes a zero-filled (uninitialized) value with an unspecified type and sets it to id.

value :

 GValue

id :

 User or group ID.

lu_value_get_id ()

id_t                lu_value_get_id                     (const GValue *value);

Get the contents of value. value should be initialized by lu_value_init_set_id() or use G_TYPE_LONG or G_TYPE_STRING.

If value does not contain a valid id_t value, LU_VALUE_INVALID_ID is returned.

value :

 GValue

Returns :

 ID value or LU_VALUE_INVALID_ID

lu_values_equal ()

int                 lu_values_equal                     (const GValue *a,
                                                         const GValue *b);

Check whether a and b have the same type and value.

a :

 GValue

b :

 GValue

Returns :

 TRUE if a and b have the same type and value
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