mojo leveldb: Add an iteration interface.

components/leveldb/public/cpp/remote_iterator.h

Index: components/leveldb/public/cpp/remote_iterator.h
diff --git a/components/leveldb/public/cpp/remote_iterator.h b/components/leveldb/public/cpp/remote_iterator.h
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+++ b/components/leveldb/public/cpp/remote_iterator.h
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+// Copyright 2016 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.
+
+#ifndef COMPONENTS_LEVELDB_PUBLIC_CPP_REMOTE_ITERATOR_H_
+#define COMPONENTS_LEVELDB_PUBLIC_CPP_REMOTE_ITERATOR_H_
+
+#include "components/leveldb/public/interfaces/leveldb.mojom.h"
+#include "mojo/public/cpp/bindings/array.h"
+#include "third_party/leveldatabase/src/include/leveldb/iterator.h"
+
+namespace leveldb {
+
+class LevelDBDatabase;
+
+// A wrapper around the raw iterator movement methods on the mojo leveldb
+// interface to allow drop in replacement to current leveldb usage.
+//
+// Note: Next(), Prev() and all the Seek*() calls cause mojo sync calls.
+class RemoteIterator : public Iterator {
+ public:
+  RemoteIterator(LevelDBDatabase* database, uint64_t iterator_id);
+  ~RemoteIterator() override;
+
+  // Overridden from leveldb::Iterator:
+  bool Valid() const override;
+  void SeekToFirst() override;
+  void SeekToLast() override;
+  void Seek(const Slice& target) override;
+  void Next() override;
+  void Prev() override;
+  Slice key() const override;
+  Slice value() const override;
+  Status status() const override;
+
+ private:
+  LevelDBDatabase* database_;
+  uint64_t iterator_id_;
+
+  bool valid_;
+  DatabaseError status_;
+  mojo::Array<uint8_t> key_;
+  mojo::Array<uint8_t> value_;
+
+  DISALLOW_COPY_AND_ASSIGN(RemoteIterator);
+};
+
+}  // namespace leveldb
+
+#endif  // COMPONENTS_LEVELDB_PUBLIC_CPP_REMOTE_ITERATOR_H_