Roll forward to cl/338482889

Signed-off-by: Alexey Polyudov <apolyudov@google.com>
Change-Id: Ic2bdb234e89f3c5860d1b483dd4bce689f13d057

cpp/platform/impl/shared/file.h

@@ -0,0 +1,67 @@
+// Copyright 2020 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     https://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef PLATFORM_IMPL_SHARED_FILE_H_
+#define PLATFORM_IMPL_SHARED_FILE_H_
+
+#include <cstdint>
+#include <fstream>
+
+#include "platform/api/input_file.h"
+#include "platform/api/output_file.h"
+#include "platform/base/exception.h"
+#include "absl/strings/string_view.h"
+
+namespace location {
+namespace nearby {
+namespace shared {
+
+class InputFile final : public api::InputFile {
+ public:
+  explicit InputFile(const std::string& path, std::int64_t size);
+  ~InputFile() override = default;
+  InputFile(InputFile&&) = default;
+  InputFile& operator=(InputFile&&) = default;
+
+  ExceptionOr<ByteArray> Read(std::int64_t size) override;
+  std::string GetFilePath() const override { return path_; }
+  std::int64_t GetTotalSize() const override { return total_size_; }
+  Exception Close() override;
+
+ private:
+  std::ifstream file_;
+  std::string path_;
+  std::int64_t total_size_;
+};
+
+class OutputFile final : public api::OutputFile {
+ public:
+  explicit OutputFile(absl::string_view path);
+  ~OutputFile() override = default;
+  OutputFile(OutputFile&&) = default;
+  OutputFile& operator=(OutputFile&&) = default;
+
+  Exception Write(const ByteArray& data) override;
+  Exception Flush() override;
+  Exception Close() override;
+
+ private:
+  std::ofstream file_;
+};
+
+}  // namespace shared
+}  // namespace nearby
+}  // namespace location
+
+#endif  // PLATFORM_IMPL_SHARED_FILE_H_