dmi_attribute_get_int
Synopsis
#include <opendmi/attribute.h>
intmax_t dmi_attribute_get_int(const dmi_attribute_t *attr, const void *value);
uintmax_t dmi_attribute_get_uint(const dmi_attribute_t *attr, const void *value);
bool dmi_attribute_get_bool(const dmi_attribute_t *attr, const void *value);
bool dmi_attribute_is_array(const dmi_attribute_t *attr);
size_t dmi_attribute_get_count(const dmi_attribute_t *attr, const void *info);
const void *dmi_attribute_get_elements(const dmi_attribute_t *attr, const void *value);Description
The functions read the members of a decoded structure the way its attributes
describe them, see DMI_ATTRIBUTE, so that a value is read without its C
type being known, e.g. by the callbacks of dmi_attributes_walk.
The dmi_attribute_get_int function reads the integer value points to as a
signed one, and the dmi_attribute_get_uint function as an unsigned one. The
width of the integer is the size of the member the attribute names,
attr→value.size, which is one of 1, 2, 4 or 8 bytes; for an element of an
array, the size is the one of an element. The value is widened to intmax_t
or uintmax_t, with the sign extended by dmi_attribute_get_int.
The dmi_attribute_get_bool function reads the bool value points to. The
attribute is not used, and may be nullptr.
The dmi_attribute_is_array function tells whether the attribute describes
several elements rather than one value: an array, declared with
DMI_ATTRIBUTE_ARRAY, whose elements are kept apart from the structure,
or a vector, declared with DMI_ATTRIBUTE_VECTOR, whose elements the
structure holds in place. The elements are then read one by one, each as a
member of its own.
The dmi_attribute_get_count function returns the number of the elements of
an array or of a vector attribute: the fixed number of a vector, or the value
of the counter member of an array, read from the structure info as an
unsigned integer of the width of the counter. The counter of an array tells
the number of the elements which have been decoded; the number is not checked
against the elements, so an array whose elements have not been allocated is
told by dmi_attribute_get_elements returning nullptr.
The dmi_attribute_get_elements function returns the first element of an
array or of a vector attribute, given the member of the attribute, value.
The member of an array points to its elements, which are kept apart from the
structure, while the elements of a vector are the member itself. Elements
follow each other attr→value.size bytes apart.
Return value
The dmi_attribute_get_int and dmi_attribute_get_uint functions return the
value of the member. They return zero if attr or value is nullptr, and
INTMAX_MAX or UINTMAX_MAX if the size of the member is not one of the
supported widths.
The dmi_attribute_get_bool function returns the value of the member, or
false if value is nullptr.
The dmi_attribute_is_array function returns true for an array or a
vector, and false otherwise or if attr is nullptr.
The dmi_attribute_get_count function returns the number of the elements. It
returns zero if attr or info is nullptr, if the attribute is neither an
array nor a vector, if the width of the counter is not supported, or if the
counter holds a number which does not fit into size_t.
The dmi_attribute_get_elements function returns the first element, or
nullptr if attr or value is nullptr, or if the elements of an array
have not been allocated.
Errors
DMI_ERROR_ARGUMENT_NULL-
Raised if
attr,valueorinfoisnullptr, except theattrofdmi_attribute_get_bool. The functions take no context, so the error reaches no error queue.
Example
The following callback of dmi_attributes_walk sums the unsigned integers
of the arrays of a structure:
static dmi_attribute_walk_t sum_array(void *context, const dmi_attribute_node_t *node)
{
const dmi_attribute_t *attr = node->attr;
const dmi_data_t *element = dmi_attribute_get_elements(attr, node->value);
if (attr->type != DMI_ATTRIBUTE_TYPE_INTEGER || element == nullptr)
return DMI_ATTRIBUTE_WALK_SKIP;
for (size_t i = 0; i < node->count; i++, element += attr->value.size)
*(uintmax_t *)context += dmi_attribute_get_uint(attr, element);
return DMI_ATTRIBUTE_WALK_SKIP;
}
static const dmi_attribute_visitor_t visitor = {
.array_start = sum_array
};