text: // Copyright 2014 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 COMPONENTS_VARIATIONS_ACTIVE_FIELD_TRIALS_H_
  #define COMPONENTS_VARIATIONS_ACTIVE_FIELD_TRIALS_H_
  
  #include <stdint.h>
  
  #include <string>
  
  #include "base/metrics/field_trial.h"
  
  namespace variations {
  
  // The Unique ID of a trial and its active group, where the name and group
  // identifiers are hashes of the trial and group name strings.
  struct ActiveGroupId {
    uint32_t name;
    uint32_t group;
  };
  
  // Returns an ActiveGroupId struct for the given trial and group names.
  ActiveGroupId MakeActiveGroupId(const std::string& trial_name,
                                  const std::string& group_name);
  
  // We need to supply a Compare class for templates since ActiveGroupId is a
  // user-defined type.
  struct ActiveGroupIdCompare {
    bool operator() (const ActiveGroupId& lhs, const ActiveGroupId& rhs) const {
      // The group and name fields are just SHA-1 Hashes, so we just need to treat
      // them as IDs and do a less-than comparison. We test group first, since
      // name is more likely to collide.
      if (lhs.group != rhs.group)
        return lhs.group < rhs.group;
      return lhs.name < rhs.name;
    }
  };
  
  // Fills the supplied vector |name_group_ids| (which must be empty when called)
  // with unique ActiveGroupIds for each Field Trial that has a chosen group.
  // Field Trials for which a group has not been chosen yet are NOT returned in
  // this list.
  void GetFieldTrialActiveGroupIds(std::vector<ActiveGroupId>* name_group_ids);
  
  // Fills the supplied vector |output| (which must be empty when called) with
  // unique string representations of ActiveGroupIds for each Field Trial that
  // has a chosen group. The strings are formatted as "<TrialName>-<GroupName>",
  // with the names as hex strings. Field Trials for which a group has not been
  // chosen yet are NOT returned in this list.
  void GetFieldTrialActiveGroupIdsAsStrings(std::vector<std::string>* output);
  
  // Expose some functions for testing. These functions just wrap functionality
  // that is implemented above.
  namespace testing {
  
  void TestGetFieldTrialActiveGroupIds(
      const base::FieldTrial::ActiveGroups& active_groups,
      std::vector<ActiveGroupId>* name_group_ids);
  
  }  // namespace testing
  
  }  // namespace variations
  
  #endif  // COMPONENTS_VARIATIONS_ACTIVE_FIELD_TRIALS_H_
  