components/variations/experiment_labels.cc

   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 #include "components/variations/experiment_labels.h"
   6
   7 #include <vector>
   8
   9 #include "base/logging.h"
  10 #include "base/strings/string_number_conversions.h"
  11 #include "base/strings/string_split.h"
  12 #include "base/strings/string_util.h"
  13 #include "base/strings/utf_string_conversions.h"
  14 #include "components/variations/variations_associated_data.h"
  15 #include "components/variations/variations_experiment_util.h"
  16
  17 namespace chrome_variations {
  18
  19 namespace {
  20
  21 const char kVariationPrefix[] = "CrVar";
  22
  23 // This method builds a single experiment label for a Chrome Variation,
  24 // including a timestamp that is a year in the future from |current_time|. Since
  25 // multiple headers can be transmitted, |count| is a number that is appended
  26 // after the label key to differentiate the labels.
  27 base::string16 CreateSingleExperimentLabel(int count,
  28                                            variations::VariationID id,
  29                                            const base::Time& current_time) {
  30   // Build the parts separately so they can be validated.
  31   const base::string16 key =
  32       base::ASCIIToUTF16(kVariationPrefix) + base::IntToString16(count);
  33   DCHECK_LE(key.size(), 8U);
  34   const base::string16 value = base::IntToString16(id);
  35   DCHECK_LE(value.size(), 8U);
  36   base::string16 label(key);
  37   label += base::ASCIIToUTF16("=");
  38   label += value;
  39   label += base::ASCIIToUTF16("|");
  40   label += variations::BuildExperimentDateString(current_time);
  41   return label;
  42 }
  43
  44 }  // namespace
  45
  46 base::string16 BuildGoogleUpdateExperimentLabel(
  47     const base::FieldTrial::ActiveGroups& active_groups) {
  48   base::string16 experiment_labels;
  49   int counter = 0;
  50
  51   const base::Time current_time(base::Time::Now());
  52
  53   // Find all currently active VariationIDs associated with Google Update.
  54   for (base::FieldTrial::ActiveGroups::const_iterator it =
  55        active_groups.begin(); it != active_groups.end(); ++it) {
  56     const variations::VariationID id =
  57         variations::GetGoogleVariationID(variations::GOOGLE_UPDATE_SERVICE,
  58                                          it->trial_name, it->group_name);
  59
  60     if (id == variations::EMPTY_ID)
  61       continue;
  62
  63     if (!experiment_labels.empty())
  64       experiment_labels += variations::kExperimentLabelSeparator;
  65     experiment_labels += CreateSingleExperimentLabel(++counter, id,
  66                                                      current_time);
  67   }
  68
  69   return experiment_labels;
  70 }
  71
  72 base::string16 ExtractNonVariationLabels(const base::string16& labels) {
  73   // First, split everything by the label separator.
  74   std::vector<base::StringPiece16> entries = base::SplitStringPiece(
  75       labels, base::StringPiece16(&variations::kExperimentLabelSeparator, 1),
  76       base::TRIM_WHITESPACE, base::SPLIT_WANT_ALL);
  77
  78   // For each label, keep the ones that do not look like a Variations label.
  79   base::string16 non_variation_labels;
  80   for (const base::StringPiece16& entry : entries) {
  81     if (entry.empty() ||
  82         base::StartsWith(entry,
  83                          base::ASCIIToUTF16(kVariationPrefix),
  84                          base::CompareCase::INSENSITIVE_ASCII)) {
  85       continue;
  86     }
  87
  88     // Dump the whole thing, including the timestamp.
  89     if (!non_variation_labels.empty())
  90       non_variation_labels += variations::kExperimentLabelSeparator;
  91     entry.AppendToString(&non_variation_labels);
  92   }
  93
  94   return non_variation_labels;
  95 }
  96
  97 base::string16 CombineExperimentLabels(const base::string16& variation_labels,
  98                                        const base::string16& other_labels) {
  99   base::StringPiece16 separator(&variations::kExperimentLabelSeparator, 1);
 100   DCHECK(!base::StartsWith(variation_labels, separator,
 101                            base::CompareCase::SENSITIVE));
 102   DCHECK(!base::EndsWith(variation_labels, separator,
 103                          base::CompareCase::SENSITIVE));
 104   DCHECK(!base::StartsWith(other_labels, separator,
 105                            base::CompareCase::SENSITIVE));
 106   DCHECK(!base::EndsWith(other_labels, separator,
 107                          base::CompareCase::SENSITIVE));
 108   // Note that if either label is empty, a separator is not necessary.
 109   base::string16 combined_labels = other_labels;
 110   if (!other_labels.empty() && !variation_labels.empty())
 111     combined_labels += variations::kExperimentLabelSeparator;
 112   combined_labels += variation_labels;
 113   return combined_labels;
 114 }
 115
 116 }  // namespace chrome_variations