Add a Restore() method to ValueStore and make StorageAPI use it

chrome/browser/value_store/leveldb_value_store.cc

 // Copyright (c) 2012 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/value_store/leveldb_value_store.h"
 
 #include "base/file_util.h"
 #include "base/json/json_reader.h"
 #include "base/json/json_writer.h"
 #include "base/logging.h"
@@ skipping 251 matching lines @@
     scoped_ptr<base::Value> next_value;
     whole_db.RemoveWithoutPathExpansion(next_key, &next_value);
     changes->push_back(
         ValueStoreChange(next_key, next_value.release(), NULL));
   }
 
   DeleteDbFile();
   return MakeWriteResult(changes.Pass());
 }
 
+bool LeveldbValueStore::Restore() {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+
+  ReadResult result = Get();
+  std::string previous_key;
+  while (result->HasError() && result->error().code == CORRUPTION) {
+    // If we don't have a specific corrupted key, or we've tried and failed to
+    // clear this specific key, or we fail to restore the key, then wipe the
+    // whole database.
+    if (!result->error().key.get() || *result->error().key == previous_key ||
+        !RestoreKey(*result->error().key)) {
+      DeleteDbFile();
+      result = Get();
+      break;
+    }
+
+    // Otherwise, re-Get() the database to check if there is still any
+    // corruption.
+    previous_key = *result->error().key;
+    result = Get();
+  }
+
+  // If we still have an error, it means we've tried deleting the database file,
+  // and failed. There's nothing more we can do.
+  return !(result->HasError() && result->error().code == CORRUPTION);
+}
+
+bool LeveldbValueStore::RestoreKey(const std::string& key) {
+  DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
+
+  ReadResult result = Get(key);
+  if (result->HasError() && result->error().code == CORRUPTION) {

[not at google - send to devlin, 2014/02/14 19:35:56]

all my talk of making corruption a switch... turns out this is a pretty frequent
pattern. how about adding a result->IsCorruption() method?

[Devlin, 2014/02/18 23:55:22]

Done.

+    leveldb::WriteBatch batch;
+    batch.Delete(key);
+    scoped_ptr<ValueStore::Error> error = WriteToDb(&batch);
+    // If we can't delete the key, the restore failed.
+    if (error.get())
+      return false;
+    result = Get(key);
+  }
+
+  // The restore succeeded if there is no corruption error.
+  return !(result->HasError() && result->error().code == CORRUPTION);

[not at google - send to devlin, 2014/02/14 19:35:56]

return !result->HasError() || result->error().code != CORRUPTION;

though see above.

[Devlin, 2014/02/18 23:55:22]

Done.

+}
+
+bool LeveldbValueStore::WriteToDbForTest(leveldb::WriteBatch* batch) {
+  scoped_ptr<ValueStore::Error> error = WriteToDb(batch);

[not at google - send to devlin, 2014/02/14 19:35:56]

inline this

[Devlin, 2014/02/18 23:55:22]

Done.

+  return !error.get();
+}
+
 scoped_ptr<ValueStore::Error> LeveldbValueStore::EnsureDbIsOpen() {
   DCHECK(BrowserThread::CurrentlyOn(BrowserThread::FILE));
 
   if (db_)
     return util::NoError();
 
   leveldb::Options options;
   options.max_open_files = 0;  // Use minimum.
   options.create_if_missing = true;
 
@@ skipping 100 matching lines @@
   CHECK(!status.ok());
   CHECK(!status.IsNotFound());  // not an error
 
   std::string message = status.ToString();
   // The message may contain |db_path_|, which may be considered sensitive
   // data, and those strings are passed to the extension, so strip it out.
   ReplaceSubstringsAfterOffset(&message, 0u, db_path_.AsUTF8Unsafe(), "...");
 
   return Error::Create(CORRUPTION, message, key.Pass());
 }