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      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 "chrome/common/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 "chrome/installer/util/google_update_experiment_util.h"
     15 #include "components/variations/variations_associated_data.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 += installer::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 += google_update::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::string16> entries;
     75   base::SplitString(labels, google_update::kExperimentLabelSeparator, &entries);
     76 
     77   // For each label, keep the ones that do not look like a Variations label.
     78   base::string16 non_variation_labels;
     79   for (std::vector<base::string16>::const_iterator it = entries.begin();
     80        it != entries.end(); ++it) {
     81     if (it->empty() ||
     82         StartsWith(*it, base::ASCIIToUTF16(kVariationPrefix), false)) {
     83       continue;
     84     }
     85 
     86     // Dump the whole thing, including the timestamp.
     87     if (!non_variation_labels.empty())
     88       non_variation_labels += google_update::kExperimentLabelSeparator;
     89     non_variation_labels += *it;
     90   }
     91 
     92   return non_variation_labels;
     93 }
     94 
     95 base::string16 CombineExperimentLabels(const base::string16& variation_labels,
     96                                        const base::string16& other_labels) {
     97   const base::string16 separator(1, google_update::kExperimentLabelSeparator);
     98   DCHECK(!StartsWith(variation_labels, separator, false));
     99   DCHECK(!EndsWith(variation_labels, separator, false));
    100   DCHECK(!StartsWith(other_labels, separator, false));
    101   DCHECK(!EndsWith(other_labels, separator, false));
    102   // Note that if either label is empty, a separator is not necessary.
    103   base::string16 combined_labels = other_labels;
    104   if (!other_labels.empty() && !variation_labels.empty())
    105     combined_labels += google_update::kExperimentLabelSeparator;
    106   combined_labels += variation_labels;
    107   return combined_labels;
    108 }
    109 
    110 }  // namespace chrome_variations
    111