Fetch AXUIElement attribute's value from a given list of attributes

AXUtility_valueOfUIElement_VA_ARGS.m

/**
 * Fetch AXUIElement attribute's value from a given list of attributes
 * @attributes              Attribute list
 * @return                  Attribute's value  NULL if failed to get
 *                          You should use CFGetTypeID() to inspect type of return value before use it
 *                          If nonnull you must release it by CFRelease()
 *
 * NOTE: must pass NULL to terminate `attributes' parameter
 *          otherwise undefined behaviour may happen
 */
+ (CFTypeRef _Nullable)valueOfUIElement:(AXUIElementRef _Nonnull)element attributes:(CFStringRef)attr1, ... {
    AXError e;
    CFTypeRef value = NULL;
    CFTypeRef *heap;
    NSUInteger i = 0;
    NSUInteger sz = 0;
    CFStringRef attr = attr1;
    va_list ap;

    ASSERT_NONNULL(element);
    ASSERT_NONNULL(attr);

    va_start(ap, attr1);
    do {
        sz++;
    } while (va_arg(ap, CFStringRef) != NULL);
    va_end(ap);

    if ((heap = (CFTypeRef *) malloc(sz * sizeof(CFTypeRef))) != NULL) {
        (void) memset(heap, 0, sz * sizeof(CFTypeRef));
    } else {
        goto out_exit;
    }

    va_start(ap, attr1);
    do {
        heap[i++] = value;

        e = AXUIElementCopyAttributeValue(element, attr, &value);
        if (e != kAXErrorSuccess) {
            LOG_ERR("AXUIElementCopyAttributeValue() fail  attribute: %@ error: %@", attr, [self axErrorName:e]);
            value = nil;
            break;
        }

        /* Stop when we met first non-AXUIElementRef value */
        if (CFGetTypeID(value) != AXUIElementGetTypeID()) {
            if (i != sz) {
                LOG_ERR("Met non-AXUIElementRef value in the interim  idx: %lu sz: %lu attr: %@", i, sz, attr);
                value = nil;
            }
            break;
        }

        element = (AXUIElementRef) value;
    } while ((attr = va_arg(ap, CFStringRef)) != NULL);
    va_end(ap);

    /* Release interim AXUIElementRef */
    for (i = 0; i < sz; i++) {
        CFSafeRelease(heap[i]);
    }
    free(heap);

out_exit:
    return value;
}