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/* Copyright Joyent, Inc. and other Node contributors. All rights reserved.
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to
 * deal in the Software without restriction, including without limitation the
 * rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
 * sell copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
 * IN THE SOFTWARE.
 */

#include <assert.h>
#include <limits.h>
#include <stdlib.h>

#if defined(__MINGW64_VERSION_MAJOR)
/* MemoryBarrier expands to __mm_mfence in some cases (x86+sse2), which may
 * require this header in some versions of mingw64. */
#include <intrin.h>
#endif

#include "uv.h"
#include "internal.h"

static void uv__once_inner(uv_once_t* guard, void (*callback)(void)) {
  DWORD result;
  HANDLE existing_event, created_event;

  created_event = CreateEvent(NULL, 1, 0, NULL);
  if (created_event == 0) {
    /* Could fail in a low-memory situation? */
    uv_fatal_error(GetLastError(), "CreateEvent");
  }

  existing_event = InterlockedCompareExchangePointer(&guard->event,
                                                     created_event,
                                                     NULL);

  if (existing_event == NULL) {
    /* We won the race */
    callback();

    result = SetEvent(created_event);
    assert(result);
    guard->ran = 1;

  } else {
    /* We lost the race. Destroy the event we created and wait for the existing
     * one to become signaled. */
    CloseHandle(created_event);
    result = WaitForSingleObject(existing_event, INFINITE);
    assert(result == WAIT_OBJECT_0);
  }
}


void uv_once(uv_once_t* guard, void (*callback)(void)) {
  /* Fast case - avoid WaitForSingleObject. */
  if (guard->ran) {
    return;
  }

  uv__once_inner(guard, callback);
}


/* Verify that uv_thread_t can be stored in a TLS slot. */
STATIC_ASSERT(sizeof(uv_thread_t) <= sizeof(void*));

static uv_key_t uv__current_thread_key;
static uv_once_t uv__current_thread_init_guard = UV_ONCE_INIT;


static void uv__init_current_thread_key(void) {
  if (uv_key_create(&uv__current_thread_key))
    abort();
}