GDataDB support with leveldb.

chrome/browser/chromeos/gdata/gdata_leveldb.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/chromeos/gdata/gdata_leveldb.h"
+
+#include <string>
+
+#include "base/logging.h"
+#include "chrome/browser/chromeos/gdata/gdata_files.h"
+#include "leveldb/write_batch.h"
+
+namespace gdata {
+namespace {
+
+const char kResourceIdPrefix[] = "id:";
+const char kPathPrefix[] = "path:";

[zel, 2012/04/25 00:49:47]

why do you need these prefixes at all?

[achuithb, 2012/04/25 00:57:53]

We're storing paths and resource_ids in the same table (this allows us to batch
the writes for atomic updates). We use the prefix to disambiguate the 2 types of
keys.

[zel, 2012/04/25 01:18:33]

you should shorten them to r: and p: instead... also when you wire things with
GFS layer, drop the first part of the path because it's the same for everything
we store "gdata/"

[achuithb, 2012/04/25 01:20:26]

Since the key is generated with GDataEntry::GetFilePath, the /gdata/ portion is
already stripped out. The keys look like
p:dir1/dir2/file1

+
+// Append prefix id: to |resource_id|.
+std::string ResourceIdToKey(const std::string& resource_id) {
+  return std::string(kResourceIdPrefix) + resource_id;
+}
+
+// Append prefix path: to |path|.
+std::string PathToKey(const FilePath& path) {
+  return std::string(kPathPrefix) + path.value();
+}
+
+GDataDB::Status GetStatus(const leveldb::Status& db_status) {
+  if (db_status.ok())
+    return GDataDB::DB_OK;
+
+  if (db_status.IsNotFound())
+    return GDataDB::DB_KEY_NOT_FOUND;
+
+  if (db_status.IsCorruption())
+    return GDataDB::DB_CORRUPTION;
+
+  if (db_status.IsIOError())
+    return GDataDB::DB_IO_ERROR;
+
+  NOTREACHED();
+  return GDataDB::DB_INTERNAL_ERROR;
+}
+
+}  // namespace
+
+GDataLevelDB::GDataLevelDB() {
+}
+
+GDataLevelDB::~GDataLevelDB() {
+}
+
+void GDataLevelDB::Init(const FilePath& db_path) {
+  leveldb::DB* level_db = NULL;
+  leveldb::Options options;
+  options.create_if_missing = true;
+  leveldb::Status db_status = leveldb::DB::Open(options,
+      db_path.Append("level_db").value(), &level_db);
+  DCHECK(level_db);
+  // TODO(achuith): If db cannot be opened, we should try to recover it.
+  // If that fails, we should just delete it and create a new file.
+  DCHECK(db_status.ok());
+  level_db_.reset(level_db);
+}
+
+GDataDB::Status GDataLevelDB::Put(const GDataEntry& entry) {
+  // Write the serialized proto.
+  std::string serialized_proto;
+  entry.SerializeToString(&serialized_proto);
+
+  leveldb::WriteBatch batch;
+  const std::string resource_id_key =
+      ResourceIdToKey(entry.resource_id());
+  const std::string path_key = PathToKey(entry.GetFilePath());
+  batch.Put(leveldb::Slice(resource_id_key), leveldb::Slice(serialized_proto));
+  // Note we store the resource_id without prefix when it's the value.
+  batch.Put(leveldb::Slice(path_key), leveldb::Slice(entry.resource_id()));
+  leveldb::Status db_status = level_db_->Write(
+      leveldb::WriteOptions(),
+      &batch);
+
+  DVLOG(1) << "GDataLevelDB::Put resource_id key = " << resource_id_key
+           << ", path key = " << path_key;
+  return GetStatus(db_status);
+}
+
+GDataDB::Status GDataLevelDB::DeleteByResourceId(
+    const std::string& resource_id) {
+  scoped_ptr<GDataEntry> entry;
+  Status status = GetByResourceId(resource_id, &entry);
+  if (status == DB_KEY_NOT_FOUND)
+    return DB_OK;
+  else if (status != DB_OK)
+    return status;
+
+  leveldb::WriteBatch batch;
+  const std::string resource_id_key = ResourceIdToKey(resource_id);
+  const std::string path_key = PathToKey(entry->GetFilePath());
+  batch.Delete(leveldb::Slice(resource_id_key));
+  batch.Delete(leveldb::Slice(path_key));
+
+  leveldb::Status db_status = level_db_->Write(leveldb::WriteOptions(),
+                                               &batch);
+  return GetStatus(db_status);
+}
+
+GDataDB::Status GDataLevelDB::DeleteByPath(
+    const FilePath& path) {
+  std::string resource_id;
+  const Status status = ResourceIdForPath(path, &resource_id);
+  if (status != DB_OK)
+    return status;
+  return DeleteByResourceId(resource_id);
+}
+
+GDataDB::Status GDataLevelDB::GetByResourceId(const std::string& resource_id,
+                                              scoped_ptr<GDataEntry>* entry) {
+  entry->reset();
+  std::string serialized_proto;
+  const std::string resource_id_key = ResourceIdToKey(resource_id);
+  const leveldb::Status db_status = level_db_->Get(leveldb::ReadOptions(),
+      leveldb::Slice(resource_id_key), &serialized_proto);
+
+  if (db_status.IsNotFound())
+    return DB_KEY_NOT_FOUND;
+
+  if (db_status.ok()) {
+    DCHECK(!serialized_proto.empty());
+    *entry = GDataEntry::FromProtoString(serialized_proto);
+    DCHECK(entry->get());
+    return DB_OK;
+  }
+  return GetStatus(db_status);
+}
+
+GDataDB::Status GDataLevelDB::GetByPath(const FilePath& path,
+                                        scoped_ptr<GDataEntry>* entry) {
+  entry->reset();
+  std::string resource_id;
+  const Status status = ResourceIdForPath(path, &resource_id);
+  if (status != DB_OK)
+    return status;
+  return GetByResourceId(resource_id, entry);
+}
+
+GDataDB::Status GDataLevelDB::ResourceIdForPath(const FilePath& path,
+                                                std::string* resource_id) {
+  const std::string path_key = PathToKey(path);
+  const leveldb::Status db_status = level_db_->Get(
+      leveldb::ReadOptions(), path_key, resource_id);
+
+  return GetStatus(db_status);
+}
+
+scoped_ptr<GDataDBIter> GDataLevelDB::CreateIterator(const FilePath& path) {
+  return scoped_ptr<GDataDBIter>(new GDataLevelDBIter(
+      scoped_ptr<leveldb::Iterator>(
+          level_db_->NewIterator(leveldb::ReadOptions())),
+      this,
+      path));
+}
+
+GDataLevelDBIter::GDataLevelDBIter(scoped_ptr<leveldb::Iterator> level_db_iter,
+                                   GDataDB* db,
+                                   const FilePath& path)
+    : level_db_iter_(level_db_iter.Pass()),
+      db_(db),
+      path_(path) {
+  const std::string path_key = PathToKey(path);
+  level_db_iter_->Seek(leveldb::Slice(path_key));
+}
+
+GDataLevelDBIter::~GDataLevelDBIter() {
+}
+
+bool GDataLevelDBIter::GetNext(std::string* path,
+                               scoped_ptr<GDataEntry>* entry) {
+  DCHECK(path);
+  DCHECK(entry);
+  path->clear();
+  entry->reset();
+
+  if (!level_db_iter_->Valid())
+    return false;
+
+  // Only consider keys under |path|.
+  const std::string path_key = PathToKey(path_);
+  leveldb::Slice key_slice(level_db_iter_->key());
+  if (!key_slice.starts_with(path_key))
+    return false;
+
+  GDataDB::Status status =
+      db_->GetByResourceId(level_db_iter_->value().ToString(), entry);
+  DCHECK_EQ(GDataDB::DB_OK, status);
+
+  key_slice.remove_prefix(sizeof(kPathPrefix) - 1);
+  path->assign(key_slice.ToString());
+
+  level_db_iter_->Next();
+  return true;
+}
+
+}  // namespace gdata