rand_util.h - mozsearch

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// Copyright (c) 2012 The Chromium Authors. All rights reserved.

// Use of this source code is governed by a BSD-style license that can be

// found in the LICENSE file.

#ifndef BASE_RAND_UTIL_H_

#define BASE_RAND_UTIL_H_

#include <stddef.h>

#include <stdint.h>

#include <algorithm>

#include <string>

#include "base/base_export.h"

#include "build/build_config.h"

namespace base {

// Returns a random number in range [0, UINT64_MAX]. Thread-safe.

BASE_EXPORT uint64_t RandUint64();

// Returns a random number between min and max (inclusive). Thread-safe.

BASE_EXPORT int RandInt(int min, int max);

// Returns a random number in range [0, range).  Thread-safe.

BASE_EXPORT uint64_t RandGenerator(uint64_t range);

// Returns a random double in range [0, 1). Thread-safe.

BASE_EXPORT double RandDouble();

// Given input |bits|, convert with maximum precision to a double in

// the range [0, 1). Thread-safe.

BASE_EXPORT double BitsToOpenEndedUnitInterval(uint64_t bits);

// Fills |output_length| bytes of |output| with random data. Thread-safe.

//

// Although implementations are required to use a cryptographically secure

// random number source, code outside of base/ that relies on this should use

// crypto::RandBytes instead to ensure the requirement is easily discoverable.

BASE_EXPORT void RandBytes(void* output, size_t output_length);

// Fills a string of length |length| with random data and returns it.

// |length| should be nonzero. Thread-safe.

//

// Note that this is a variation of |RandBytes| with a different return type.

// The returned string is likely not ASCII/UTF-8. Use with care.

//

// Although implementations are required to use a cryptographically secure

// random number source, code outside of base/ that relies on this should use

// crypto::RandBytes instead to ensure the requirement is easily discoverable.

BASE_EXPORT std::string RandBytesAsString(size_t length);

// An STL UniformRandomBitGenerator backed by RandUint64.

// TODO(tzik): Consider replacing this with a faster implementation.

class RandomBitGenerator {

 public:

  using result_type = uint64_t;

  static constexpr result_type min() { return 0; }

  static constexpr result_type max() { return UINT64_MAX; }

  result_type operator()() const { return RandUint64(); }

  RandomBitGenerator() = default;

  ~RandomBitGenerator() = default;

};

// Shuffles [first, last) randomly. Thread-safe.

template <typename Itr>

void RandomShuffle(Itr first, Itr last) {

  std::shuffle(first, last, RandomBitGenerator());

#if defined(OS_POSIX)

BASE_EXPORT int GetUrandomFD();

#endif

}  // namespace base

#endif  // BASE_RAND_UTIL_H_