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Eliminates arc4random.

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It seems not to be as portable as I'd hoped.
This commit is contained in:
Thomas Harte 2018-05-14 20:01:20 -04:00
parent 9f2f388e5a
commit 76802b5e38
1 changed files with 15 additions and 3 deletions
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18
Storage/Disk/Drive.cpp
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@ -12,16 +12,28 @@
#include <algorithm>
#include <cassert>
#include <cstdlib>
#include <cmath>
#include <chrono>
#include <random>
using namespace Storage::Disk;
Drive::Drive(unsigned int input_clock_rate, int revolutions_per_minute, int number_of_heads):
Storage::TimedEventLoop(input_clock_rate),
rotational_multiplier_(60, revolutions_per_minute),
available_heads_(number_of_heads),
random_source_(static_cast<uint64_t>(arc4random()) | (static_cast<uint64_t>(arc4random()) << 32)) {
available_heads_(number_of_heads){
rotational_multiplier_.simplify();
const auto seed = static_cast<std::default_random_engine::result_type>(std::chrono::system_clock::now().time_since_epoch().count());
std::default_random_engine randomiser(seed);
// Get at least 64 bits of random information; rounding is likey to give this a slight bias.
random_source_ = 0;
auto half_range = (randomiser.max() - randomiser.min()) / 2;
for(int bit = 0; bit < 64; ++bit) {
random_source_ <<= 1;
random_source_ |= ((randomiser() - randomiser.min()) >= half_range) ? 1 : 0;
}
}
Drive::~Drive() {