func (st *state) callOffset(c byte) {
	if c == 0 {
		if len(st.str) == 0 {
			st.fail("missing call offset")
		}
		c = st.str[0]
		st.advance(1)
	}
	switch c {
	case 'h':
		st.number()
	case 'v':
		st.number()
		if len(st.str) == 0 || st.str[0] != '_' {
			st.fail("expected _ after number")
		}
		st.advance(1)
		st.number()
	default:
		st.failEarlier("unrecognized call offset code", 1)
	}
	if len(st.str) == 0 || st.str[0] != '_' {
		st.fail("expected _ after call offset")
	}
	st.advance(1)
}
func (st *state) callOffset(c byte) {
	if c == 0 {
		if len(st.str) == 0 {
			st.fail("missing call offset")
		}
		c = st.str[0]
		st.advance(1)
	}
	switch c {
	case 'h':
		st.number()
	case 'v':
		st.number()
		if len(st.str) == 0 || st.str[0] != '_' {
			st.fail("expected _ after number")
		}
		st.advance(1)
		st.number()
	default:
		st.failEarlier("unrecognized call offset code", 1)
	}
	if len(st.str) == 0 || st.str[0] != '_' {
		st.fail("expected _ after call offset")
	}
	st.advance(1)
}
// <call-offset> ::= h <nv-offset> _
//               ::= v <v-offset> _
//
// <nv-offset> ::= <(offset) number>
//
// <v-offset> ::= <(offset) number> _ <(virtual offset) number>
//
// The c parameter, if not 0, is a character we just read which is the
// start of the <call-offset>.
//
// We don't display the offset information anywhere.