lock.h

// Start of lock.h.

// A very simple cross-platform implementation of locks.  Uses
// pthreads on Unix and some Windows thing there.  Futhark's
// host-level code is not multithreaded, but user code may be, so we
// need some mechanism for ensuring atomic access to API functions.
// This is that mechanism.  It is not exposed to user code at all, so
// we do not have to worry about name collisions.

#ifdef _WIN32

typedef HANDLE lock_t;

static lock_t create_lock(lock_t *lock) {
  *lock = CreateMutex(NULL,  // Default security attributes.
                      FALSE, // Initially unlocked.
                      NULL); // Unnamed.
}

static void lock_lock(lock_t *lock) {
  assert(WaitForSingleObject(*lock, INFINITE) == WAIT_OBJECT_0);
}

static void lock_unlock(lock_t *lock) {
  assert(ReleaseMutex(*lock));
}

static void free_lock(lock_t *lock) {
  CloseHandle(*lock);
}

#else
// Assuming POSIX

#include <pthread.h>

typedef pthread_mutex_t lock_t;

static void create_lock(lock_t *lock) {
  int r = pthread_mutex_init(lock, NULL);
  assert(r == 0);
}

static void lock_lock(lock_t *lock) {
  int r = pthread_mutex_lock(lock);
  assert(r == 0);
}

static void lock_unlock(lock_t *lock) {
  int r = pthread_mutex_unlock(lock);
  assert(r == 0);
}

static void free_lock(lock_t *lock) {
  // Nothing to do for pthreads.
  (void)lock;
}

#endif

// End of lock.h.