watchos/Kernel.h

struct Task
{
  int pid = 0;
  bool running = false;
  int exit_code = 0;
  int (*callback)(int, unsigned int);
  unsigned long run_interval = 0;
  unsigned long run_accumulator = 0;
  unsigned int signal = 0;
  unsigned int signal_pending = 0;
  unsigned int signal_mask = 0xFFFF;
};

void Kernel_setup();
void Kernel_tick();

// Panic and stop everything
void Kernel_panic(char* message);

// Start a new process
int Kernel_start(int (*callback)(int, unsigned int), unsigned long interval);
// Continue execution of a process
void Kernel_enable(int pid);
// Pause execution of a process
void Kernel_disable(int pid);
// Clean up exited process
void Kernel_reap(int pid);

// Send a signal to a/all processes
void Kernel_signal(int pid, unsigned int signal);
void Kernel_signal(unsigned int signal);

// Set a tasks's signal mask
void Kernel_signal_mask(int pid, unsigned int signal_mask);

// Get the run interval of a process
unsigned long Kernel_get_run_interval(int pid);
void Kernel_set_run_interval(int pid, unsigned long interval);

// Count how many tasks are running
int Kernel_count_running_tasks();

// Check if process has exited
bool Kernel_is_exited(int pid);
// Get exit code of process
int Kernel_get_exit_code(int pid);

// Check if a button was pressed
bool Kernel_read_input(int input);
// Get how long *actually* elapsed since the last tick since we don't provide hard guarantees
unsigned long Kernel_get_last_tick_duration();

#define SIGNAL_NONE     0x0000
#define SIGNAL_TICK     0x0001
#define SIGNAL_START    0x0002
#define SIGNAL_STOP     0x0004
#define SIGNAL_INPUT_A  0x0008
#define SIGNAL_INPUT_B  0x0010
#define SIGNAL_REDRAW   0x0020

#define KERNEL_INPUT_BUTTON_A 0
#define KERNEL_INPUT_BUTTON_B 1