#include <futex.h>
#include <stdarg.h>
#include <errno.h>
#include "syscall.h"

// Wasm doesn't *yet* have futex(), but it's being planned as part of the
// threaded-Wasm support in Spring 2018.
//
// For now, Wasm is single-threaded and we simply assert that the lock is not
// held, and abort if a wait would be required (assume it's a corrupted lock).

long __syscall_futex(long arg1, ...)
{
  va_list va;
  va_start(va, arg1);

  volatile int* addr = (volatile int*)arg1;
  long op = va_arg(va, long);

  op &= ~FUTEX_PRIVATE;

  if (op == FUTEX_WAIT) {
    int val = (int)va_arg(va, long);
    // arg4 would be the timeout as a timespec*
    va_end(va);

    if (*addr == val) {
      // trap, Wasm can't block
      // TODO use a WebAssembly futex builtin, when those arrive!
      __builtin_unreachable();
    }
    return 0;
  }
  if (op == FUTEX_WAKE) {
    // arg3 would be the number of waiters to wake as an int
    va_end(va);

    // Wasm can't block/wait
    // TODO use a WebAssembly futex builtin, when those arrive!
    return 0;
  }

  va_end(va);
  return -ENOSYS;
}