util/crypto_util/random.h

// Copyright 2016 The Fuchsia Authors
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//    http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

#ifndef COBALT_UTIL_CRYPTO_UTIL_RANDOM_H_
#define COBALT_UTIL_CRYPTO_UTIL_RANDOM_H_

#include <cstdint>
#include <string>

#include "util/crypto_util/types.h"

namespace cobalt {

namespace crypto {

// An instance of Random provides some utility functions for retrieving
// randomness.
class Random {
 public:
  virtual ~Random() {}

  // Writes |num| bytes of random data from a uniform distribution to buf.
  // The caller must ensure that |buf| has enough space.
  virtual void RandomBytes(byte *buf, std::size_t num);

  // Writes |buf->size()| bytes of random data from a uniform distribution
  // into buf.
  void RandomString(std::string* buf);

  // Returns a uniformly random integer in the range [0, 2^32-1].
  uint32_t RandomUint32();

  // Returns a uniformly random integer in the range [0, 2^64-1].
  uint64_t RandomUint64();

  // Returns 8 independent random bits. For each bit the probability of being
  // equal to one is the given p. p must be in the range [0.0, 1.0] or the
  // result is undefined. p will be rounded to the nearest value of the form
  // n/(2^32) where n is an integer in the range [0, 2^32].
  byte RandomBits(float p);
};

}  // namespace crypto

}  // namespace cobalt

#endif  // COBALT_UTIL_CRYPTO_UTIL_RANDOM_H_