dmi_attribute_is_unspecified

Synopsis

#include <opendmi/attribute.h>

bool dmi_attribute_is_unspecified(const dmi_attribute_t *attr, const void *value);
bool dmi_attribute_is_unknown(const dmi_attribute_t *attr, const void *value);

Description

The specification reserves values of many fields which stand for no value at all: "unspecified", for the ones the firmware gives no value, and "unknown", for the ones it does not know. An attribute names them by its .unspec and .unknown parameters, see DMI_ATTRIBUTE, so that they are written as such rather than as values, e.g. by the output formats of the command line tool.

The dmi_attribute_is_unspecified function tells whether the member value points to is unspecified:

if the attribute has an .unspec value, the member is compared with it byte by byte, over the size of the member, attr→value.size;
otherwise, a string is unspecified if its pointer is nullptr, a handle if it is DMI_HANDLE_INVALID, and binary data if its length is zero;
a value of any other type is never unspecified without an .unspec value.

The dmi_attribute_is_unknown function tells whether the member is unknown, by comparing it with the .unknown value of the attribute byte by byte, over the size of the member. A value is never unknown if the attribute has no .unknown value.

For an element of an array, the size of the member is the one of an element, so the element is compared the same way.

Parameters

attr: Attribute describing the member.
value: Member to check.

Return value

Returns true if the value stands for "unspecified" or "unknown", and false otherwise or if attr or value is nullptr.

Errors

DMI_ERROR_ARGUMENT_NULL: Raised if attr or value is nullptr. The functions take no context, so the error reaches no error queue.

Example

static bool print_value(void *context, const dmi_attribute_node_t *node)
{
    dmi_context_t *dmi = context;

    if (dmi_attribute_is_unspecified(node->attr, node->value)) {
        puts("Not specified");
    } else if (dmi_attribute_is_unknown(node->attr, node->value)) {
        puts("Unknown");
    } else {
        char *text = dmi_attribute_format(dmi, node->attr, node->value, true);

        puts(text != nullptr ? text : "?");
        dmi_free(text);
    }

    return true;
}