[Sync] Implement encryption-aware conflict resolution.

chrome/browser/sync/syncable/directory_backing_store.cc

 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "chrome/browser/sync/syncable/directory_backing_store.h"
 
 #include "build/build_config.h"
 
 #include <limits>
 
@@ skipping 24 matching lines @@
 using std::string;
 
 namespace syncable {
 
 // This just has to be big enough to hold an UPDATE or INSERT statement that
 // modifies all the columns in the entry table.
 static const string::size_type kUpdateStatementBufferSize = 2048;
 
 // Increment this version whenever updating DB tables.
 extern const int32 kCurrentDBVersion;  // Global visibility for our unittest.
-const int32 kCurrentDBVersion = 77;
+const int32 kCurrentDBVersion = 78;
 
 namespace {
 
 int ExecQuery(sqlite3* dbhandle, const char* query) {
   sqlite_utils::SQLStatement statement;
   int result = statement.prepare(dbhandle, query);
   if (SQLITE_OK != result)
     return result;
   do {
     result = statement.step();
@@ skipping 413 matching lines @@
       version_on_disk = 76;
   }
 
   // Version 77 standardized all time fields to ms since the Unix
   // epoch.
   if (version_on_disk == 76) {
     if (MigrateVersion76To77())
       version_on_disk = 77;
   }
 
+  // Version 78 added the column prev_server_specifics to the metas table.
+  if (version_on_disk == 77) {
+    if (MigrateVersion77To78())
+      version_on_disk = 78;
+  }
+
   // If one of the migrations requested it, drop columns that aren't current.
   // It's only safe to do this after migrating all the way to the current
   // version.
   if (version_on_disk == kCurrentDBVersion && needs_column_refresh_) {
     if (!RefreshColumns())
       version_on_disk = 0;
   }
 
   // A final, alternative catch-all migration to simply re-sync everything.
   if (version_on_disk != kCurrentDBVersion) {
@@ skipping 622 matching lines @@
       TO_UNIX_TIME_MS(server_mtime) ", "
       TO_UNIX_TIME_MS(ctime) ", "
       TO_UNIX_TIME_MS(server_ctime));
 #undef TO_UNIX_TIME_MS
   if (update_timestamps.step() != SQLITE_DONE)
     return false;
   SetVersion(77);
   return true;
 }
 
+bool DirectoryBackingStore::MigrateVersion77To78() {
+  // Version 78 added one column to table 'metas': prev_server_specifics.
+  int result =
+      ExecQuery(load_dbhandle_,
+                "ALTER TABLE metas ADD COLUMN prev_server_specifics BLOB");
+  if (result != SQLITE_DONE)
+    return false;
+  SetVersion(78);
+  return true;
+}
+
 int DirectoryBackingStore::CreateTables() {
   DVLOG(1) << "First run, creating tables";
   // Create two little tables share_version and share_info
   int result = ExecQuery(load_dbhandle_,
                          "CREATE TABLE share_version ("
                          "id VARCHAR(128) primary key, data INT)");
   if (result != SQLITE_DONE)
     return result;
   {
     sqlite_utils::SQLStatement statement;
@@ skipping 126 matching lines @@
       "id TEXT primary key, "
       "name TEXT, "
       "store_birthday TEXT, "
       "db_create_version TEXT, "
       "db_create_time INT, "
       "next_id INT default -2, "
       "cache_guid TEXT )");
   return ExecQuery(load_dbhandle_, query.c_str());
 }
 }  // namespace syncable