src/timer.c


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#include <stdint.h>
#include <go32.h>
#include <dpmi.h>
#include <stddef.h>

volatile uint32_t ubox_ticks = 0;
volatile uint32_t clock = 0;
volatile uint8_t clock_secs = 0;
volatile uint8_t clock_enabled = 0;
volatile uint8_t *clock_updated = NULL;
volatile void (*user_fn)(void) = NULL;

static _go32_dpmi_seginfo old_handler, new_handler;

static void timer_handler()
{
    ubox_ticks++;

    if (clock_enabled)
    {
        clock += 5494;
        if (clock > 100000)
        {
            clock -= 100000;
            if (clock_secs)
            {
                clock_secs--;
                if (clock_updated)
                    *clock_updated = 1;
            }
        }
    }

    if (user_fn)
        user_fn();
}

void ubox_timer_init()
{
    _go32_dpmi_get_protected_mode_interrupt_vector(0x1c, &old_handler);
    new_handler.pm_offset = (unsigned long)timer_handler;
    new_handler.pm_selector = _go32_my_cs();
    _go32_dpmi_chain_protected_mode_interrupt_vector(0x1c, &new_handler);
}

void ubox_timer_user_fn(void (*fn)(void))
{
    user_fn = fn;
}

void ubox_timer_free()
{
    _go32_dpmi_set_protected_mode_interrupt_vector(0x1c, &old_handler);
}

void ubox_timer_start(uint8_t secs, volatile uint8_t *updated)
{
    *updated = 0;
    clock_updated = updated;
    clock_secs = secs;
    clock_enabled = 1;
}

uint8_t ubox_timer_value()
{
    *clock_updated = 0;
    return clock_secs;
}

void ubox_timer_stop()
{
    clock_enabled = 0;
}

void ubox_timer_resume()
{
    clock_enabled = 1;
}