dmi_attribute_resolve

Synopsis

#include <opendmi/attribute.h>

const dmi_attribute_t *dmi_attribute_resolve(const dmi_attribute_t *attr, const void *info);

Description

The dmi_attribute_resolve function returns the attribute which describes the value of the member attr declares in the decoded structure info.

An attribute of any type but a variant one describes its value itself, and is returned as it is. The member of a variant attribute holds the selector rather than the value, see DMI_ATTRIBUTE_VARIANT: the selector is read from info as a signed integer of the width of the member, and the variant whose selector it equals is returned, or the default variant if no other one matches. The value is then read, checked and formatted with the attribute returned, e.g. by dmi_attribute_format, while the variant attribute keeps naming the member, since the code, the name and the level of a variant are not used.

dmi_attributes_walk resolves the attributes on its own, and gives the callbacks both of them.

The attribute returned belongs to the specification, and must not be freed.

Parameters

attr: Attribute to resolve.
info: Decoded structure holding the member, e.g. the info member of an entity.

Return value

Returns attr if it is not a variant attribute, and the variant matching the selector or the default variant otherwise. Returns nullptr if no variant matches and there is no default one, which means the structure holds no value for the attribute, or if attr or info is nullptr, or if attr is a variant attribute without .variants.

Errors

DMI_ERROR_ARGUMENT_NULL: Raised if attr or info is nullptr. The function takes no context, so the error reaches no error queue.
DMI_ERROR_ARGUMENT_INVALID: Raised if attr is a variant attribute whose .variants is nullptr, and reaches no error queue either.

Example

const dmi_data_t *info = entity->info;
const dmi_attribute_t *value_attr = dmi_attribute_resolve(attr, info);

if (value_attr != nullptr) {
    char *text = dmi_attribute_format(context, value_attr,
                                      info + value_attr->value.offset, true);

    if (text != nullptr) {
        printf("%s: %s\n", dmi_attribute_name(attr, entity->spec->code), text);
        dmi_free(text);
    }
}