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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, VariationID id,
     28                                            const base::Time& current_time) {
     29   // Build the parts separately so they can be validated.
     30   const base::string16 key =
     31       base::ASCIIToUTF16(kVariationPrefix) + base::IntToString16(count);
     32   DCHECK_LE(key.size(), 8U);
     33   const base::string16 value = base::IntToString16(id);
     34   DCHECK_LE(value.size(), 8U);
     35   base::string16 label(key);
     36   label += base::ASCIIToUTF16("=");
     37   label += value;
     38   label += base::ASCIIToUTF16("|");
     39   label += installer::BuildExperimentDateString(current_time);
     40   return label;
     41 }
     42 
     43 }  // namespace
     44 
     45 base::string16 BuildGoogleUpdateExperimentLabel(
     46     const base::FieldTrial::ActiveGroups& active_groups) {
     47   base::string16 experiment_labels;
     48   int counter = 0;
     49 
     50   const base::Time current_time(base::Time::Now());
     51 
     52   // Find all currently active VariationIDs associated with Google Update.
     53   for (base::FieldTrial::ActiveGroups::const_iterator it =
     54        active_groups.begin(); it != active_groups.end(); ++it) {
     55     const VariationID id = GetGoogleVariationID(GOOGLE_UPDATE_SERVICE,
     56                                                 it->trial_name, it->group_name);
     57 
     58     if (id == EMPTY_ID)
     59       continue;
     60 
     61     if (!experiment_labels.empty())
     62       experiment_labels += google_update::kExperimentLabelSeparator;
     63     experiment_labels += CreateSingleExperimentLabel(++counter, id,
     64                                                      current_time);
     65   }
     66 
     67   return experiment_labels;
     68 }
     69 
     70 base::string16 ExtractNonVariationLabels(const base::string16& labels) {
     71   // First, split everything by the label separator.
     72   std::vector<base::string16> entries;
     73   base::SplitString(labels, google_update::kExperimentLabelSeparator, &entries);
     74 
     75   // For each label, keep the ones that do not look like a Variations label.
     76   base::string16 non_variation_labels;
     77   for (std::vector<base::string16>::const_iterator it = entries.begin();
     78        it != entries.end(); ++it) {
     79     if (it->empty() ||
     80         StartsWith(*it, base::ASCIIToUTF16(kVariationPrefix), false)) {
     81       continue;
     82     }
     83 
     84     // Dump the whole thing, including the timestamp.
     85     if (!non_variation_labels.empty())
     86       non_variation_labels += google_update::kExperimentLabelSeparator;
     87     non_variation_labels += *it;
     88   }
     89 
     90   return non_variation_labels;
     91 }
     92 
     93 base::string16 CombineExperimentLabels(const base::string16& variation_labels,
     94                                        const base::string16& other_labels) {
     95   const base::string16 separator(1, google_update::kExperimentLabelSeparator);
     96   DCHECK(!StartsWith(variation_labels, separator, false));
     97   DCHECK(!EndsWith(variation_labels, separator, false));
     98   DCHECK(!StartsWith(other_labels, separator, false));
     99   DCHECK(!EndsWith(other_labels, separator, false));
    100   // Note that if either label is empty, a separator is not necessary.
    101   base::string16 combined_labels = other_labels;
    102   if (!other_labels.empty() && !variation_labels.empty())
    103     combined_labels += google_update::kExperimentLabelSeparator;
    104   combined_labels += variation_labels;
    105   return combined_labels;
    106 }
    107 
    108 }  // namespace chrome_variations
    109