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/*
* Copyright (c) 2020, Andreas Kling <kling@serenityos.org>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <AK/Platform.h>
#include <AK/Span.h>
#include <AK/StdLibExtras.h>
#include <AK/Types.h>
#include <stdlib.h>
#if defined(__unix__)
# include <unistd.h>
#endif
#if defined(AK_OS_MACOS)
# include <sys/random.h>
#endif
namespace AK {
inline void fill_with_random([[maybe_unused]] Bytes bytes)
{
#if defined(AK_OS_SERENITY) || defined(AK_OS_ANDROID)
arc4random_buf(bytes.data(), bytes.size());
#elif defined(OSS_FUZZ)
#else
auto fill_with_random_fallback = [&]() {
for (auto& byte : bytes)
byte = rand();
};
# if defined(__unix__) or defined(AK_OS_MACOS)
// The maximum permitted value for the getentropy length argument.
static constexpr size_t getentropy_length_limit = 256;
auto iterations = bytes.size() / getentropy_length_limit;
for (size_t i = 0; i < iterations; ++i) {
if (getentropy(bytes.data(), getentropy_length_limit) != 0) {
fill_with_random_fallback();
return;
}
bytes = bytes.slice(getentropy_length_limit);
}
if (bytes.is_empty() || getentropy(bytes.data(), bytes.size()) == 0)
return;
# endif
fill_with_random_fallback();
#endif
}
template<typename T>
inline T get_random()
{
T t;
fill_with_random({ &t, sizeof(T) });
return t;
}
u32 get_random_uniform(u32 max_bounds);
template<typename Collection>
inline void shuffle(Collection& collection)
{
// Fisher-Yates shuffle
for (size_t i = collection.size() - 1; i >= 1; --i) {
size_t j = get_random_uniform(i + 1);
AK::swap(collection[i], collection[j]);
}
}
}
#if USING_AK_GLOBALLY
using AK::fill_with_random;
using AK::get_random;
using AK::get_random_uniform;
using AK::shuffle;
#endif
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