45 lines
1.3 KiB
C++
45 lines
1.3 KiB
C++
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// Copyright 2015 Google Inc. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// IMPORTANT: This is for demo /simulation purposes only. Use a better random
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// function in production applications.
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#include "libc_rand_impl.h"
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#include <assert.h>
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#include <stdint.h> // uint64_t
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#include <stdlib.h> // srand
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namespace rappor {
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//
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// LibcRand
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//
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// Similar to client/python/fastrand.c
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bool LibcRand::GetMask(float prob, int num_bits, Bits* mask_out) const {
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int rand_threshold = static_cast<int>(prob * RAND_MAX);
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Bits mask = 0;
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for (int i = 0; i < num_bits; ++i) {
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// NOTE: could use rand_r(), which is more thread-safe
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Bits bit = (rand() < rand_threshold);
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mask |= (bit << i);
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}
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*mask_out = mask;
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return true; // no possible failure
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}
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} // namespace rappor
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