chromium/components/variations/entropy_provider.h

// Copyright 2012 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef COMPONENTS_VARIATIONS_ENTROPY_PROVIDER_H_
#define COMPONENTS_VARIATIONS_ENTROPY_PROVIDER_H_

#include <stddef.h>
#include <stdint.h>

#include <cstdint>
#include <optional>
#include <string>
#include <string_view>

#include "base/component_export.h"
#include "base/metrics/field_trial.h"

namespace variations {

// SHA1EntropyProvider is an entropy provider suitable for high entropy sources.
// It works by taking the first 64 bits of the SHA1 hash of the entropy source
// concatenated with the trial name, or randomization seed and using that for
// the final entropy value.
class COMPONENT_EXPORT(VARIATIONS) SHA1EntropyProvider
    : public base::FieldTrial::EntropyProvider { … };

// A |value| in the range [0, range).
struct ValueInRange { … };

// NormalizedMurmurHashEntropyProvider is an entropy provider suitable for low
// entropy sources (below 16 bits). It uses MurmurHash3_32 to hash the study
// name along with all possible low entropy sources. It finds the index where
// the actual low entropy source's hash would fall in the sorted list of all
// those hashes, and uses that as the final value. For more info, see:
// https://docs.google.com/document/d/1cPF5PruriWNP2Z5gSkq4MBTm0wSZqLyIJkUO9ekibeo
//
// Note: this class should be kept consistent with
// NormalizedMurmurHashEntropyProvider on the Java side.
class COMPONENT_EXPORT(VARIATIONS) NormalizedMurmurHashEntropyProvider final
    : public base::FieldTrial::EntropyProvider { … };

class SessionEntropyProvider : public base::FieldTrial::EntropyProvider { … };

class COMPONENT_EXPORT(VARIATIONS) EntropyProviders { … };

}  // namespace variations

#endif  // COMPONENTS_VARIATIONS_ENTROPY_PROVIDER_H_