var byte queue_start = 0
var byte queue_len = 0
var byte queue_base
var byte q0 = 0
var byte q1 = 0
var byte q2 = 0
var byte q3 = 0
var byte q4 = 0
var byte q5 = 0
var byte q6 = 0
var byte q7 = 0
-- global since parameter passing in interrupts is broken
var byte q_param
var byte __tmp_q

procedure queue_init is
    asm movlw q0
    asm movwf queue_base
    queue_start = 0
    queue_len   = 0
end procedure

procedure queue_put is
    if queue_len < 8 then
        assembler
            movf queue_start, w
            addwf queue_len, w
            andlw 7
            addwf queue_base, w
            movwf fsr
            movf q_param, w
            movwf indf
            incf queue_len, f
        end assembler
    end if
end procedure

procedure queue_get is
    if queue_len > 0 then
        assembler
            movf queue_start, w
            addwf queue_base, w
            movwf fsr
            movf indf, w
            movwf q_param
            incf queue_start, w
            andlw 7
            movwf queue_start
            decf queue_len, f
        end assembler
    end if
end procedure