45 lines
1.3 KiB
C++
45 lines
1.3 KiB
C++
// Copyright 2015 Google Inc. All rights reserved.
|
|
//
|
|
// Licensed 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.
|
|
|
|
// IMPORTANT: This is for demo /simulation purposes only. Use a better random
|
|
// function in production applications.
|
|
|
|
#include "libc_rand_impl.h"
|
|
|
|
#include <assert.h>
|
|
#include <stdint.h> // uint64_t
|
|
#include <stdlib.h> // srand
|
|
|
|
namespace rappor {
|
|
|
|
//
|
|
// LibcRand
|
|
//
|
|
|
|
// Similar to client/python/fastrand.c
|
|
bool LibcRand::GetMask(float prob, int num_bits, Bits* mask_out) const {
|
|
int rand_threshold = static_cast<int>(prob * RAND_MAX);
|
|
Bits mask = 0;
|
|
|
|
for (int i = 0; i < num_bits; ++i) {
|
|
// NOTE: could use rand_r(), which is more thread-safe
|
|
Bits bit = (rand() < rand_threshold);
|
|
mask |= (bit << i);
|
|
}
|
|
*mask_out = mask;
|
|
return true; // no possible failure
|
|
}
|
|
|
|
} // namespace rappor
|