gecko-dev/xpcom/base/nsUUIDGenerator.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#if defined(XP_WIN)
#include <windows.h>
#include <objbase.h>
#elif defined(XP_MACOSX)
#include <CoreFoundation/CoreFoundation.h>
#else
#include <stdlib.h>
#include "prrng.h"
#endif

#include "nsUUIDGenerator.h"

using namespace mozilla;

NS_IMPL_ISUPPORTS(nsUUIDGenerator, nsIUUIDGenerator)

nsUUIDGenerator::nsUUIDGenerator()
  : mLock("nsUUIDGenerator.mLock")
{
}

nsUUIDGenerator::~nsUUIDGenerator()
{
}

nsresult
nsUUIDGenerator::Init()
{
  // We're a service, so we're guaranteed that Init() is not going
  // to be reentered while we're inside Init().

#if !defined(XP_WIN) && !defined(XP_MACOSX) && !defined(ANDROID)
  /* initialize random number generator using NSPR random noise */
  unsigned int seed;

  size_t bytes = 0;
  while (bytes < sizeof(seed)) {
    size_t nbytes = PR_GetRandomNoise(((unsigned char *)&seed)+bytes,
                                      sizeof(seed)-bytes);
    if (nbytes == 0) {
      return NS_ERROR_FAILURE;
    }
    bytes += nbytes;
  }

  /* Initialize a new RNG state, and immediately switch
   * back to the previous one -- we want to use mState
   * only for our own calls to random().
   */
  mSavedState = initstate(seed, mState, sizeof(mState));
  setstate(mSavedState);

  mRBytes = 4;
#ifdef RAND_MAX
  if ((unsigned long) RAND_MAX < (unsigned long)0xffffffff)
    mRBytes = 3;
  if ((unsigned long) RAND_MAX < (unsigned long)0x00ffffff)
    mRBytes = 2;
  if ((unsigned long) RAND_MAX < (unsigned long)0x0000ffff)
    mRBytes = 1;
  if ((unsigned long) RAND_MAX < (unsigned long)0x000000ff)
    return NS_ERROR_FAILURE;
#endif

#endif /* non XP_WIN and non XP_MACOSX */

  return NS_OK;
}

NS_IMETHODIMP
nsUUIDGenerator::GenerateUUID(nsID** ret)
{
  nsID *id = static_cast<nsID*>(NS_Alloc(sizeof(nsID)));
  if (id == nullptr)
    return NS_ERROR_OUT_OF_MEMORY;

  nsresult rv = GenerateUUIDInPlace(id);
  if (NS_FAILED(rv)) {
    NS_Free(id);
    return rv;
  }

  *ret = id;
  return rv;
}

NS_IMETHODIMP
nsUUIDGenerator::GenerateUUIDInPlace(nsID* id)
{
  // The various code in this method is probably not threadsafe, so lock
  // across the whole method.
  MutexAutoLock lock(mLock);

#if defined(XP_WIN)
  HRESULT hr = CoCreateGuid((GUID*)id);
  if (FAILED(hr))
    return NS_ERROR_FAILURE;
#elif defined(XP_MACOSX)
  CFUUIDRef uuid = CFUUIDCreate(kCFAllocatorDefault);
  if (!uuid)
    return NS_ERROR_FAILURE;

  CFUUIDBytes bytes = CFUUIDGetUUIDBytes(uuid);
  memcpy(id, &bytes, sizeof(nsID));

  CFRelease(uuid);
#else /* not windows or OS X; generate randomness using random(). */
  /* XXX we should be saving the return of setstate here and switching
   * back to it; instead, we use the value returned when we called
   * initstate, since older glibc's have broken setstate() return values
   */
#ifndef ANDROID
  setstate(mState);
#endif

  size_t bytesLeft = sizeof(nsID);
  while (bytesLeft > 0) {
#ifdef ANDROID
    long rval = arc4random();
    const size_t mRBytes = 4;
#else
    long rval = random();
#endif


    uint8_t *src = (uint8_t*)&rval;
    // We want to grab the mRBytes least significant bytes of rval, since
    // mRBytes less than sizeof(rval) means the high bytes are 0.
#ifdef IS_BIG_ENDIAN
    src += sizeof(rval) - mRBytes;
#endif
    uint8_t *dst = ((uint8_t*) id) + (sizeof(nsID) - bytesLeft);
    size_t toWrite = (bytesLeft < mRBytes ? bytesLeft : mRBytes);
    for (size_t i = 0; i < toWrite; i++)
      dst[i] = src[i];

    bytesLeft -= toWrite;
  }

  /* Put in the version */
  id->m2 &= 0x0fff;
  id->m2 |= 0x4000;

  /* Put in the variant */
  id->m3[0] &= 0x3f;
  id->m3[0] |= 0x80;

#ifndef ANDROID
  /* Restore the previous RNG state */
  setstate(mSavedState);
#endif
#endif

  return NS_OK;
}