pagespeed/kernel/util/simple_random.cc

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 * 
 *   http://www.apache.org/licenses/LICENSE-2.0
 * 
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */


#include "pagespeed/kernel/base/abstract_mutex.h"
#include "pagespeed/kernel/base/scoped_ptr.h"
#include "pagespeed/kernel/util/simple_random.h"

namespace net_instaweb {

uint32 SimpleRandom::Next() {
  ScopedMutex lock(mutex_.get());
  return NextLockHeld();
}

uint32 SimpleRandom::NextLockHeld() {
  z_ = 36969 * (z_ & 65535) + (z_ >> 16);
  w_ = 18000 * (w_ & 65535) + (w_ >> 16);
  uint32 pseudo_random_number = (z_ << 16) + w_;
  return pseudo_random_number;
}

GoogleString SimpleRandom::GenerateHighEntropyString(int size) {
  ScopedMutex lock(mutex_.get());
  GoogleString value;
  value.reserve(size);
  for (int i = 0; i < size; ++i) {
    value.push_back(static_cast<char>(NextLockHeld() & 0xff));
  }
  return value;
}

}  // namespace net_instaweb