2 * Copyright 2013 Facebook, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
17 #include "folly/Random.h"
26 std::atomic<uint32_t> seedInput(0);
29 uint32_t randomNumberSeed() {
31 gettimeofday(&tv, NULL);
32 const uint32_t kPrime0 = 51551;
33 const uint32_t kPrime1 = 61631;
34 const uint32_t kPrime2 = 64997;
35 const uint32_t kPrime3 = 111857;
36 return kPrime0 * (seedInput++)
37 + kPrime1 * static_cast<uint32_t>(getpid())
38 + kPrime2 * static_cast<uint32_t>(tv.tv_sec)
39 + kPrime3 * static_cast<uint32_t>(tv.tv_usec);