chrome/installer/util/language_selector.cc

   1 // Copyright (c) 2012 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 // This file defines a helper class for selecting a supported language from a
   6 // set of candidates.
   7
   8 #include "chrome/installer/util/language_selector.h"
   9
  10 #include <algorithm>
  11 #include <functional>
  12
  13 #include "base/logging.h"
  14 #include "base/strings/string_util.h"
  15 #include "base/win/i18n.h"
  16 #include "chrome/installer/util/google_update_settings.h"
  17
  18 #include "installer_util_strings.h"
  19
  20 namespace {
  21
  22 struct LangToOffset {
  23   const wchar_t* language;
  24   int offset;
  25 };
  26
  27 // The language we fall back upon when all else fails.
  28 const wchar_t kFallbackLanguage[] = L"en-us";
  29 const int kFallbackLanguageOffset = IDS_L10N_OFFSET_EN_US;
  30
  31 // http://tools.ietf.org/html/rfc5646 Section 2.3.3
  32 const std::wstring::size_type kScriptSubtagLength = 4;
  33
  34 // A sorted array of language identifiers (and their offsets) for which
  35 // translations are available. The contents of the array are generated by
  36 // create_string_rc.py.
  37 const LangToOffset kLanguageOffsetPairs[] = {
  38 #define HANDLE_LANGUAGE(l_, o_) { L ## #l_, o_ },
  39   DO_LANGUAGES
  40 #undef HANDLE_LANGUAGE
  41 };
  42
  43 // A sorted array of language identifiers that are aliases to other languages
  44 // for which translations are available.
  45 const LangToOffset kLanguageToOffsetExceptions[] = {
  46   // Alias some English variants to British English (all others wildcard to US).
  47   { L"en-au", IDS_L10N_OFFSET_EN_GB },
  48   { L"en-ca", IDS_L10N_OFFSET_EN_GB },
  49   { L"en-nz", IDS_L10N_OFFSET_EN_GB },
  50   { L"en-za", IDS_L10N_OFFSET_EN_GB },
  51   // Alias es-es to es (all others wildcard to es-419).
  52   { L"es-es", IDS_L10N_OFFSET_ES },
  53   // Google web properties use iw for he. Handle both just to be safe.
  54   { L"he", IDS_L10N_OFFSET_IW },
  55   // Google web properties use no for nb. Handle both just to be safe.
  56   { L"nb", IDS_L10N_OFFSET_NO },
  57   // Some Google web properties use tl for fil. Handle both just to be safe.
  58   // They're not completely identical, but alias it here.
  59   { L"tl", IDS_L10N_OFFSET_FIL },
  60   // Pre-Vista aliases for Chinese w/ script subtag.
  61   { L"zh-chs", IDS_L10N_OFFSET_ZH_CN },
  62   { L"zh-cht", IDS_L10N_OFFSET_ZH_TW },
  63   // Vista+ aliases for Chinese w/ script subtag.
  64   { L"zh-hans", IDS_L10N_OFFSET_ZH_CN },
  65   { L"zh-hant", IDS_L10N_OFFSET_ZH_TW },
  66   // Alias Hong Kong and Macau to Taiwan.
  67   { L"zh-hk", IDS_L10N_OFFSET_ZH_TW },
  68   { L"zh-mo", IDS_L10N_OFFSET_ZH_TW },
  69   // Although the wildcard entry for zh would result in this, alias zh-sg so
  70   // that it will win if it precedes another valid tag in a list of candidates.
  71   { L"zh-sg", IDS_L10N_OFFSET_ZH_CN }
  72 };
  73
  74 // A sorted array of neutral language identifiers that are wildcard aliases to
  75 // other languages for which translations are available.
  76 const LangToOffset kLanguageToOffsetWildcards[] = {
  77   // Use the U.S. region for anything English.
  78   { L"en", IDS_L10N_OFFSET_EN_US },
  79   // Use the Latin American region for anything Spanish.
  80   { L"es", IDS_L10N_OFFSET_ES_419 },
  81   // Use the Brazil region for anything Portugese.
  82   { L"pt", IDS_L10N_OFFSET_PT_BR },
  83   // Use the P.R.C. region for anything Chinese.
  84   { L"zh", IDS_L10N_OFFSET_ZH_CN }
  85 };
  86
  87 #if !defined(NDEBUG)
  88 // Returns true if the items in the given range are sorted.  If
  89 // |byNameAndOffset| is true, the items must be sorted by both name and offset.
  90 bool IsArraySorted(const LangToOffset* first, const LangToOffset* last,
  91                    bool byNameAndOffset) {
  92   if (last - first > 1) {
  93     for (--last; first != last; ++first) {
  94        if (!(std::wstring(first->language) < (first + 1)->language) ||
  95            byNameAndOffset && !(first->offset < (first + 1)->offset)) {
  96          return false;
  97        }
  98     }
  99   }
 100   return true;
 101 }
 102
 103 // Validates that the static read-only mappings are properly sorted.
 104 void ValidateMappings() {
 105   // Ensure that kLanguageOffsetPairs is sorted.
 106   DCHECK(IsArraySorted(&kLanguageOffsetPairs[0],
 107                        &kLanguageOffsetPairs[arraysize(kLanguageOffsetPairs)],
 108                        true)) << "kOffsetToLanguageId is not sorted";
 109
 110   // Ensure that kLanguageToOffsetExceptions is sorted.
 111   DCHECK(IsArraySorted(
 112            &kLanguageToOffsetExceptions[0],
 113            &kLanguageToOffsetExceptions[arraysize(kLanguageToOffsetExceptions)],
 114            false)) << "kLanguageToOffsetExceptions is not sorted";
 115
 116   // Ensure that kLanguageToOffsetWildcards is sorted.
 117   DCHECK(IsArraySorted(
 118             &kLanguageToOffsetWildcards[0],
 119             &kLanguageToOffsetWildcards[arraysize(kLanguageToOffsetWildcards)],
 120             false)) << "kLanguageToOffsetWildcards is not sorted";
 121 }
 122 #endif  // !defined(NDEBUG)
 123
 124 // A less-than overload to do slightly more efficient searches in the
 125 // sorted arrays.
 126 bool operator<(const LangToOffset& left, const std::wstring& right) {
 127   return left.language < right;
 128 }
 129
 130 // A less-than overload to do slightly more efficient searches in the
 131 // sorted arrays.
 132 bool operator<(const std::wstring& left, const LangToOffset& right) {
 133   return left < right.language;
 134 }
 135
 136 // A not-so-efficient less-than overload for the same uses as above.
 137 bool operator<(const LangToOffset& left, const LangToOffset& right) {
 138   return std::wstring(left.language) < right.language;
 139 }
 140
 141 // A compare function for searching in a sorted array by offset.
 142 bool IsOffsetLessThan(const LangToOffset& left, const LangToOffset& right) {
 143   return left.offset < right.offset;
 144 }
 145
 146 // Binary search in one of the sorted arrays to find the offset corresponding to
 147 // a given language |name|.
 148 bool TryFindOffset(const LangToOffset* first, const LangToOffset* last,
 149                    const std::wstring& name, int* offset) {
 150   const LangToOffset* search_result = std::lower_bound(first, last, name);
 151   if (last != search_result && search_result->language == name) {
 152     *offset = search_result->offset;
 153     return true;
 154   }
 155   return false;
 156 }
 157
 158 // A predicate function for LanguageSelector::SelectIf that searches for the
 159 // offset of a translated language.  The search first tries to find an exact
 160 // match.  Failing that, an exact match with an alias is attempted.
 161 bool GetLanguageOffset(const std::wstring& language, int* offset) {
 162   // Note: always perform the exact match first so that an alias is never
 163   // selected in place of a future translation.
 164   return
 165       TryFindOffset(
 166           &kLanguageOffsetPairs[0],
 167           &kLanguageOffsetPairs[arraysize(kLanguageOffsetPairs)],
 168           language, offset) ||
 169       TryFindOffset(
 170           &kLanguageToOffsetExceptions[0],
 171           &kLanguageToOffsetExceptions[arraysize(kLanguageToOffsetExceptions)],
 172           language, offset);
 173 }
 174
 175 // A predicate function for LanguageSelector::SelectIf that searches for a
 176 // wildcard match with |language|'s primary language subtag.
 177 bool MatchLanguageOffset(const std::wstring& language, int* offset) {
 178   std::wstring primary_language = language.substr(0, language.find(L'-'));
 179
 180   // Now check for wildcards.
 181   return
 182       TryFindOffset(
 183           &kLanguageToOffsetWildcards[0],
 184           &kLanguageToOffsetWildcards[arraysize(kLanguageToOffsetWildcards)],
 185           primary_language, offset);
 186 }
 187
 188 // Adds to |candidates| the eligible languages on the system.  Any language
 189 // setting specified by Omaha takes precedence over the operating system's
 190 // configured languages.
 191 void GetCandidatesFromSystem(std::vector<std::wstring>* candidates) {
 192   DCHECK(candidates);
 193   std::wstring language;
 194
 195   // Omaha gets first pick.
 196   GoogleUpdateSettings::GetLanguage(&language);
 197   if (!language.empty()) {
 198     candidates->push_back(language);
 199   }
 200
 201   // Now try the Windows UI languages.  Use the thread preferred since that will
 202   // kindly return us a list of all kinds of fallbacks.
 203   base::win::i18n::GetThreadPreferredUILanguageList(candidates);
 204 }
 205
 206 }  // namespace
 207
 208 namespace installer {
 209
 210 LanguageSelector::LanguageSelector()
 211     : offset_(arraysize(kLanguageOffsetPairs)) {
 212 #if !defined(NDEBUG)
 213   ValidateMappings();
 214 #endif  // !defined(NDEBUG)
 215   std::vector<std::wstring> candidates;
 216
 217   GetCandidatesFromSystem(&candidates);
 218   DoSelect(candidates);
 219 }
 220
 221 LanguageSelector::LanguageSelector(const std::vector<std::wstring>& candidates)
 222     : offset_(arraysize(kLanguageOffsetPairs)) {
 223 #if !defined(NDEBUG)
 224   ValidateMappings();
 225 #endif  // !defined(NDEBUG)
 226   DoSelect(candidates);
 227 }
 228
 229 LanguageSelector::~LanguageSelector() {
 230 }
 231
 232 // static
 233 std::wstring LanguageSelector::GetLanguageName(int offset) {
 234   DCHECK_GE(offset, 0);
 235   DCHECK_LT(static_cast<size_t>(offset), arraysize(kLanguageOffsetPairs));
 236
 237   LangToOffset value = { NULL, offset };
 238   const LangToOffset* search_result =
 239     std::lower_bound(&kLanguageOffsetPairs[0],
 240                      &kLanguageOffsetPairs[arraysize(kLanguageOffsetPairs)],
 241                      value, IsOffsetLessThan);
 242   if (&kLanguageOffsetPairs[arraysize(kLanguageOffsetPairs)] != search_result &&
 243       search_result->offset == offset) {
 244     return search_result->language;
 245   }
 246   NOTREACHED() << "Unknown language offset.";
 247   return std::wstring(&kFallbackLanguage[0], arraysize(kFallbackLanguage) - 1);
 248 }
 249
 250 // Runs through the set of candidates, sending their downcased representation
 251 // through |select_predicate|.  Returns true if the predicate selects a
 252 // candidate, in which case |matched_name| is assigned the value of the
 253 // candidate and |matched_offset| is assigned the language offset of the
 254 // selected translation.
 255 // static
 256 bool LanguageSelector::SelectIf(const std::vector<std::wstring>& candidates,
 257                                 SelectPred_Fn select_predicate,
 258                                 std::wstring* matched_name,
 259                                 int* matched_offset) {
 260   std::wstring candidate;
 261   for (std::vector<std::wstring>::const_iterator scan = candidates.begin(),
 262           end = candidates.end(); scan != end; ++scan) {
 263     candidate.assign(*scan);
 264     StringToLowerASCII(&candidate);
 265     if (select_predicate(candidate, matched_offset)) {
 266       matched_name->assign(*scan);
 267       return true;
 268     }
 269   }
 270
 271   return false;
 272 }
 273
 274 // Select the best-fit translation from the ordered list |candidates|.
 275 // At the conclusion, this instance's |matched_candidate_| and |offset_| members
 276 // are set to the name of the selected candidate and the offset of the matched
 277 // translation.  If no translation is selected, the fallback's name and offset
 278 // are selected.
 279 void LanguageSelector::DoSelect(const std::vector<std::wstring>& candidates) {
 280   // Make a pass through the candidates looking for an exact or alias match.
 281   // Failing that, make another pass looking for a wildcard match.
 282   if (!SelectIf(candidates, &GetLanguageOffset, &matched_candidate_,
 283                 &offset_) &&
 284       !SelectIf(candidates, &MatchLanguageOffset, &matched_candidate_,
 285                 &offset_)) {
 286     VLOG(1) << "No suitable language found for any candidates.";
 287
 288     // Our fallback is "en-us"
 289     matched_candidate_.assign(&kFallbackLanguage[0],
 290                               arraysize(kFallbackLanguage) - 1);
 291     offset_ = kFallbackLanguageOffset;
 292   }
 293 }
 294
 295 }  // namespace installer