1 // Copyright 2015 Google Inc. All rights reserved. 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 15 // IMPORTANT: This is for demo /simulation purposes only. Use a better random 16 // function in production applications. 17 18 #include "libc_rand_impl.h" 19 20 #include <assert.h> 21 #include <stdint.h> // uint64_t 22 #include <stdlib.h> // srand 23 24 namespace rappor { 25 26 // 27 // LibcRand 28 // 29 30 // Similar to client/python/fastrand.c GetMask(float prob,int num_bits,Bits * mask_out) const31bool LibcRand::GetMask(float prob, int num_bits, Bits* mask_out) const { 32 int rand_threshold = static_cast<int>(prob * RAND_MAX); 33 Bits mask = 0; 34 35 for (int i = 0; i < num_bits; ++i) { 36 // NOTE: could use rand_r(), which is more thread-safe 37 Bits bit = (rand() < rand_threshold); 38 mask |= (bit << i); 39 } 40 *mask_out = mask; 41 return true; // no possible failure 42 } 43 44 } // namespace rappor 45