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      1 // Copyright 2013 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/metrics/variations/experiment_labels.h"
      6 
      7 #include "base/logging.h"
      8 #include "base/strings/string_number_conversions.h"
      9 #include "base/strings/string_split.h"
     10 #include "base/strings/string_util.h"
     11 #include "base/strings/utf_string_conversions.h"
     12 #include "chrome/installer/util/google_update_experiment_util.h"
     13 #include "components/variations/variations_associated_data.h"
     14 
     15 namespace chrome_variations {
     16 
     17 namespace {
     18 
     19 const char kVariationPrefix[] = "CrVar";
     20 
     21 // This method builds a single experiment label for a Chrome Variation,
     22 // including a timestamp that is a year in the future from |current_time|. Since
     23 // multiple headers can be transmitted, |count| is a number that is appended
     24 // after the label key to differentiate the labels.
     25 base::string16 CreateSingleExperimentLabel(int count, VariationID id,
     26                                            const base::Time& current_time) {
     27   // Build the parts separately so they can be validated.
     28   const base::string16 key =
     29       ASCIIToUTF16(kVariationPrefix) + base::IntToString16(count);
     30   DCHECK_LE(key.size(), 8U);
     31   const base::string16 value = base::IntToString16(id);
     32   DCHECK_LE(value.size(), 8U);
     33   base::string16 label(key);
     34   label += ASCIIToUTF16("=");
     35   label += value;
     36   label += ASCIIToUTF16("|");
     37   label += installer::BuildExperimentDateString(current_time);
     38   return label;
     39 }
     40 
     41 }  // namespace
     42 
     43 base::string16 BuildGoogleUpdateExperimentLabel(
     44     const base::FieldTrial::ActiveGroups& active_groups) {
     45   base::string16 experiment_labels;
     46   int counter = 0;
     47 
     48   const base::Time current_time(base::Time::Now());
     49 
     50   // Find all currently active VariationIDs associated with Google Update.
     51   for (base::FieldTrial::ActiveGroups::const_iterator it =
     52        active_groups.begin(); it != active_groups.end(); ++it) {
     53     const VariationID id = GetGoogleVariationID(GOOGLE_UPDATE_SERVICE,
     54                                                 it->trial_name, it->group_name);
     55 
     56     if (id == EMPTY_ID)
     57       continue;
     58 
     59     if (!experiment_labels.empty())
     60       experiment_labels += ASCIIToUTF16(google_update::kExperimentLabelSep);
     61     experiment_labels += CreateSingleExperimentLabel(++counter, id,
     62                                                      current_time);
     63   }
     64 
     65   return experiment_labels;
     66 }
     67 
     68 base::string16 ExtractNonVariationLabels(const base::string16& labels) {
     69   const base::string16 separator =
     70       ASCIIToUTF16(google_update::kExperimentLabelSep);
     71   base::string16 non_variation_labels;
     72 
     73   // First, split everything by the label separator.
     74   std::vector<base::string16> entries;
     75   base::SplitStringUsingSubstr(labels, separator, &entries);
     76 
     77   // For each label, keep the ones that do not look like a Variations label.
     78   for (std::vector<base::string16>::const_iterator it = entries.begin();
     79        it != entries.end(); ++it) {
     80     if (it->empty() || StartsWith(*it, ASCIIToUTF16(kVariationPrefix), false))
     81       continue;
     82 
     83     // Dump the whole thing, including the timestamp.
     84     if (!non_variation_labels.empty())
     85       non_variation_labels += separator;
     86     non_variation_labels += *it;
     87   }
     88 
     89   return non_variation_labels;
     90 }
     91 
     92 base::string16 CombineExperimentLabels(const base::string16& variation_labels,
     93                                        const base::string16& other_labels) {
     94   const base::string16 separator =
     95       ASCIIToUTF16(google_update::kExperimentLabelSep);
     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 += separator;
    104   combined_labels += variation_labels;
    105   return combined_labels;
    106 }
    107 
    108 }  // namespace chrome_variations
    109