Building the equivalent of a C structure in RubyCocoa

Question

I'm trying to do something similar to this code sample but in RubyCocoa. In particular, I'm having some trouble trying to build a SecKeychainAttributeList. I suspect I need to make use of Array#pack or something to build a suitable structure in Ruby. Any advice on how to build the equivalent of attributes in the following chunk of code would be very welcome :-

void addInternetPassword(NSString *password, NSString *account,
                    NSString *server, NSString *itemLabel, NSString *path,
                    SecProtocolType protocol, int port)
{
    OSStatus err;
    SecKeychainItemRef item = nil;
    const char *pathUTF8 = [path UTF8String];
    const char *serverUTF8 = [server UTF8String];
    const char *accountUTF8 = [account UTF8String];
    const char *passwordUTF8 = [password UTF8String];
    const char *itemLabelUTF8 = [itemLabel UTF8String];

    //Create initial access control settings for the item:
    SecAccessRef access = createAccess(itemLabel);

    //Following is the lower-level equivalent to the
    // SecKeychainAddInternetPassword function:

    //Set up the attribute vector (each attribute consists
    // of {tag, length, pointer}):
    SecKeychainAttribute attrs[] = {
        { kSecLabelItemAttr, strlen(itemLabelUTF8), (char *)itemLabelUTF8 },
        { kSecAccountItemAttr, strlen(accountUTF8), (char *)accountUTF8 },
        { kSecServerItemAttr, strlen(serverUTF8), (char *)serverUTF8 },
        { kSecPortItemAttr, sizeof(int), (int *)&port },
        { kSecProtocolItemAttr, sizeof(SecProtocolType),
                                        (SecProtocolType *)&protocol },
        { kSecPathItemAttr, strlen(pathUTF8), (char *)pathUTF8 }
    };
    SecKeychainAttributeList attributes = { sizeof(attrs) / sizeof(attrs[0]),
                                                                attrs };