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;; IRQ0 HANDLER (TIMER INTERRUPT) ;;

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align 32

irq0:

        save_ring3_context

	mov   ax, os_data

	mov   ds, ax

	mov   es, ax

        inc   dword [timer_ticks]

        mov   eax, [timer_ticks]

        call  playNote           ; <<<--- Speaker driver

        cmp   eax,[next_usage_update]

        jb    .nocounter

        add   eax,100

        mov   [next_usage_update],eax

        call  updatecputimes

     .nocounter:

        cmp   [DONT_SWITCH], byte 1

        jne   .change_task

        mov   al,0x20   ; send End Of Interrupt signal

        mov   dx,0x20

        out   dx,al

        mov   [DONT_SWITCH], byte 0

        restore_ring3_context

        iret

     .change_task:

        call  update_counters

        call  find_next_task

        mov   ecx, eax

        mov   al,0x20   ; send End Of Interrupt signal

        mov   dx,0x20

        out   dx,al

	test  ecx, ecx  ; if there is only one running process

        jnz   .return

        call  do_change_task

     .return:

        restore_ring3_context

        iret

align 4

change_task:

        pushfd

        cli

        pushad

        call  update_counters

; \begin{Mario79}

        cmp     [dma_task_switched], 1

        jne     .find_next_task

        mov     [dma_task_switched], 0

        mov     ebx, [dma_process]

        cmp     [CURRENT_TASK], ebx

        je      .return

        mov     edi, [dma_slot_ptr]

        mov     [CURRENT_TASK], ebx

        mov     [TASK_BASE], edi

        jmp     @f

.find_next_task:

; \end{Mario79}

        call  find_next_task

        test  eax, eax    ; the same task -> skip switch

        jnz    .return

@@:

        mov   [DONT_SWITCH],byte 1

        call  do_change_task

     .return:

        popad

        popfd

        ret

uglobal

   align 4

   far_jump:

    .offs dd ?

    .sel  dw ?

   context_counter     dd ? ;noname & halyavin

   next_usage_update   dd ?

   timer_ticks         dd ?

   prev_slot           dd ?

   event_sched         dd ?

endg

update_counters:

        mov   edi, [TASK_BASE]

        mov   ebx, [edi+TASKDATA.counter_add] ; time stamp counter add

        call  _rdtsc

        sub   eax, ebx

        add   eax, [edi+TASKDATA.counter_sum] ; counter sum

        mov   [edi+TASKDATA.counter_sum], eax

ret

; Find next task to execute

; result: ebx = number of the selected task

;         eax = 1  if the task is the same

;         edi = address of the data for the task in ebx

;         [0x3000] = ebx and [0x3010] = edi

;         corrupts other regs

find_next_task:

        mov   ebx, [CURRENT_TASK]

        mov   edi, [TASK_BASE]

        mov   [prev_slot], ebx

      .waiting_for_termination:

      .waiting_for_reuse:

      .waiting_for_event:

      .suspended:

        cmp   ebx, [TASK_COUNT]

        jb    @f

        mov   edi, CURRENT_TASK

        xor   ebx, ebx

      @@:

        add   edi,0x20

        inc   ebx

        mov   al, byte [edi+TASKDATA.state]

        test  al, al

        jz    .found

	cmp   al, 1

	jz    .suspended

	cmp   al, 2

	jz    .suspended

        cmp   al, 3

        je    .waiting_for_termination

        cmp   al, 4

        je    .waiting_for_termination

        cmp   al, 9

        je    .waiting_for_reuse

        mov   [CURRENT_TASK],ebx

        mov   [TASK_BASE],edi

        cmp   al, 5

        jne   .noevents

        call  get_event_for_app

        test  eax, eax

        jz    .waiting_for_event

        mov   [event_sched], eax

        mov   [edi+TASKDATA.state], byte 0

      .noevents:

      .found:

        mov   [CURRENT_TASK],ebx

        mov   [TASK_BASE],edi

        call  _rdtsc

        mov   [edi+TASKDATA.counter_add],eax

	xor   eax, eax

        cmp   ebx, [prev_slot]

        sete  al

ret

; in: ebx = TSS selector index

do_change_task:

        shl   ebx, 3

        xor   eax, eax

        add   ebx, tss0

        mov   [far_jump.sel],  bx   ; selector

        mov   [far_jump.offs], eax  ; offset

        jmp   pword [far_jump]

        inc   [context_counter] ;noname & halyavin

ret

align 4

updatecputimes:

        mov  eax,[idleuse]

        mov  [idleusesec],eax

        mov  [idleuse],dword 0

        mov  ecx, [TASK_COUNT]

        mov  edi, TASK_DATA

      .newupdate:

        mov  ebx,[edi+TASKDATA.counter_sum]

        mov  [edi+TASKDATA.cpu_usage],ebx

        mov  [edi+TASKDATA.counter_sum],dword 0

        add  edi,0x20

        dec  ecx

        jnz  .newupdate

        ret