gistfile1.txt

typedef struct {
  int fds[2];
} lamelock_t;

void lamelock_release(lamelock_t* lock);

int lamelock_init(lamelock_t* lock) {
  char data = 42;
  
  if (pipe(&lock->fds) < 0)
    return -1;
    
  if (lamelock_release(lock) < 0) {
    close(lock->fds[0]);
    close(lock->fds[1]);
    return -1;
  }
  return 0;
}

void lamelock_destroy(lamelock_t* lock) {
  close(lock->fds[0]);
  close(lock->fds[1]);
}

void lamelock_acquire(lamelock_t* lock) {
  int r;
  char data;
  
  do {
    r = read(lock->fds[1], &data, sizeof data);
  } (while r < 0 && errno == EINTR);
  
  if (r < 0)
    return -1;
    
  return 0;
}

void lamelock_release(lamelock_t* lock) {
  char data = 42;
  int r;
  
  do {
    r = write(lock->fds[0], &data, sizeof data);
  } while (r < 0 && errno == EINTR);
  
  if (r < 0)
    return -1;
  
  return 0;
}