components/variations/active_field_trials.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef COMPONENTS_VARIATIONS_ACTIVE_FIELD_TRIALS_H_
   6 #define COMPONENTS_VARIATIONS_ACTIVE_FIELD_TRIALS_H_
   7
   8 #include <string>
   9
  10 #include "base/basictypes.h"
  11 #include "base/metrics/field_trial.h"
  12
  13 namespace variations {
  14
  15 // The Unique ID of a trial and its active group, where the name and group
  16 // identifiers are hashes of the trial and group name strings.
  17 struct ActiveGroupId {
  18   uint32 name;
  19   uint32 group;
  20 };
  21
  22 // Returns an ActiveGroupId struct for the given trial and group names.
  23 ActiveGroupId MakeActiveGroupId(const std::string& trial_name,
  24                                 const std::string& group_name);
  25
  26 // We need to supply a Compare class for templates since ActiveGroupId is a
  27 // user-defined type.
  28 struct ActiveGroupIdCompare {
  29   bool operator() (const ActiveGroupId& lhs, const ActiveGroupId& rhs) const {
  30     // The group and name fields are just SHA-1 Hashes, so we just need to treat
  31     // them as IDs and do a less-than comparison. We test group first, since
  32     // name is more likely to collide.
  33     if (lhs.group != rhs.group)
  34       return lhs.group < rhs.group;
  35     return lhs.name < rhs.name;
  36   }
  37 };
  38
  39 // Fills the supplied vector |name_group_ids| (which must be empty when called)
  40 // with unique ActiveGroupIds for each Field Trial that has a chosen group.
  41 // Field Trials for which a group has not been chosen yet are NOT returned in
  42 // this list.
  43 void GetFieldTrialActiveGroupIds(std::vector<ActiveGroupId>* name_group_ids);
  44
  45 // Fills the supplied vector |output| (which must be empty when called) with
  46 // unique string representations of ActiveGroupIds for each Field Trial that
  47 // has a chosen group. The strings are formatted as "<TrialName>-<GroupName>",
  48 // with the names as hex strings. Field Trials for which a group has not been
  49 // chosen yet are NOT returned in this list.
  50 void GetFieldTrialActiveGroupIdsAsStrings(std::vector<std::string>* output);
  51
  52 // Expose some functions for testing. These functions just wrap functionality
  53 // that is implemented above.
  54 namespace testing {
  55
  56 void TestGetFieldTrialActiveGroupIds(
  57     const base::FieldTrial::ActiveGroups& active_groups,
  58     std::vector<ActiveGroupId>* name_group_ids);
  59
  60 }  // namespace testing
  61
  62 }  // namespace variations
  63
  64 #endif  // COMPONENTS_VARIATIONS_ACTIVE_FIELD_TRIALS_H_