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Code Issues 150 Wiki Activity

seed the random engines from the system pool, not std::random_device

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This commit is contained in:
maj00r
2026-09-14 17:34:59 +02:00
parent c3007e3237
commit ff3daea78c
5 changed files with 53 additions and 10 deletions
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29
utilities/utilities.cpp
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@@ -15,6 +15,8 @@ Copyright (C) 2007-2014 Maciej Cierniak
//
//#include <sys/types.h>
//#include <sys/stat.h>
#include <charconv>
#include <ctime>
#include <ranges>
//#ifndef WIN32
//#include <unistd.h>
@@ -30,7 +32,6 @@ Copyright (C) 2007-2014 Maciej Cierniak
#include "utilities/U8.h"
//#include "utilities/Logs.h"
// TODO: This shouldn't be in Globals?
bool DebugModeFlag = false;
@@ -137,15 +138,35 @@ int Random(int min, int max)
return dist(Global.random_engine);
}
std::uint32_t clock_seed()
{
static std::atomic<std::uint32_t> nth{0};
return static_cast<std::uint32_t>(std::time({})) + nth.fetch_add(1, std::memory_order_relaxed);
}
std::uint32_t seed_of(std::string const &Text)
{
std::uint32_t number{};
if (std::from_chars(Text.data(), Text.data() + Text.size(), number).ec == std::errc{})
{
return number;
}
std::uint32_t hash{};
for (auto const character : Text)
{
hash = hash * 31u + static_cast<std::uint32_t>(static_cast<unsigned char>(character));
}
return hash;
}
std::string generate_uuid_v4()
{
std::random_device rd;
std::mt19937 gen(rd());
static thread_local std::mt19937 generator{clock_seed()};
std::uniform_int_distribution<int> dist(0, 255);
std::array<uint8_t, 16> bytes;
for (auto &b : bytes)
b = static_cast<uint8_t>(dist(gen));
b = static_cast<uint8_t>(dist(generator));
// UUID v4 (RFC 4122)
bytes[6] = bytes[6] & 0x0F | 0x40;

11
utilities/utilities.h
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@@ -62,6 +62,17 @@ inline long Round(double const f)
double Random(double a, double b);
int Random(int min, int max);
// Seed for the random engines: the clock, plus a counter so two engines seeded in
// the same second do not come out the same.
std::uint32_t clock_seed();
// The seed a word stands for. A number is taken as it is written; anything else is
// hashed the way Java's String.hashCode does it, so the same word gives the same
// world on every platform and every build - which is the whole point of telling
// somebody a seed.
std::uint32_t seed_of(std::string const &Text);
std::string generate_uuid_v4();
double LocalRandom(double a, double b);

3
utilities/uuid.hpp
View File

@@ -6,6 +6,7 @@
#include <string>
#include <algorithm>
#include <cstdint>
#include "utilities/utilities.h"
class UID {
public:
@@ -13,7 +14,7 @@ public:
static UID random() {
static thread_local std::mt19937_64 gen(std::random_device{}());
static thread_local std::mt19937_64 gen{clock_seed()};
UID u;
uint64_t a = gen();
uint64_t b = gen();