#include <pthread.h>
#include "libc.h"

static struct atfork_funcs {
  void (*prepare)(void);
  void (*parent)(void);
  void (*child)(void);
  struct atfork_funcs *prev, *next;
} * funcs;

static volatile int lock[2];

void __fork_handler(int who) {
  struct atfork_funcs* p;
  if (!funcs)
    return;
  if (who < 0) {
    LOCK(lock);
    for (p = funcs; p; p = p->next) {
      if (p->prepare)
        p->prepare();
      funcs = p;
    }
  } else {
    for (p = funcs; p; p = p->prev) {
      if (!who && p->parent)
        p->parent();
      else if (who && p->child)
        p->child();
      funcs = p;
    }
    UNLOCK(lock);
  }
}

int pthread_atfork(void (*prepare)(void),
                   void (*parent)(void),
                   void (*child)(void)) {
  struct atfork_funcs* new = malloc(sizeof *new);
  if (!new)
    return -1;

  LOCK(lock);
  new->next = funcs;
  new->prev = 0;
  new->prepare = prepare;
  new->parent = parent;
  new->child = child;
  if (funcs)
    funcs->prev = new;
  funcs = new;
  UNLOCK(lock);
  return 0;
}