typedef enum { ... } SilcAttributeContact;

    The defined preferred contact methods defined by the specification.
    This is bit mask.

    typedef enum {
      SILC_ATTRIBUTE_CONTACT_NONE    = 0x00000000,    /* no specific method */
      SILC_ATTRIBUTE_CONTACT_EMAIL   = 0x00000001,    /* email preferred */
      SILC_ATTRIBUTE_CONTACT_CALL    = 0x00000002,    /* phone call preferred */
      SILC_ATTRIBUTE_CONTACT_PAGE    = 0x00000004,    /* "paging" preferred */
      SILC_ATTRIBUTE_CONTACT_SMS     = 0x00000008,    /* SMS preferred */
      SILC_ATTRIBUTE_CONTACT_MMS     = 0x00000010,    /* MMS preferred */
      SILC_ATTRIBUTE_CONTACT_CHAT    = 0x00000020,    /* chatting preferred */
      SILC_ATTRIBUTE_CONTACT_VIDEO   = 0x00000040,    /* video conferencing */
    } SilcAttributeContact;