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// 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
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