Added base implementation for input_file and output_file

This are unimplemented currently, but will be in the future.

internal/platform/implementation/linux/output_file.h

@@ -0,0 +1,45 @@
+// 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_LINUX_OUTPUT_FILE_H_
+#define PLATFORM_IMPL_LINUX_OUTPUT_FILE_H_
+
+#include "internal/platform/implementation/output_file.h"
+#include "internal/platform/byte_array.h"
+#include "internal/platform/exception.h"
+
+namespace nearby {
+namespace linux {
+
+// An OutputFile represents a writable file on the system.
+class OutputFile : public api::OutputFile {
+ public:
+  // TODO(b/184975123): replace with real implementation.
+  ~OutputFile() override = default;
+
+  // throws Exception::kIo
+  // TODO(b/184975123): replace with real implementation.
+  Exception Write(const ByteArray& data) override { return Exception{}; }
+  // throws Exception::kIo
+  // TODO(b/184975123): replace with real implementation.
+  Exception Flush() override { return Exception{}; }
+  // throws Exception::kIo
+  // TODO(b/184975123): replace with real implementation.
+  Exception Close() override { return Exception{}; }
+};
+
+}  // namespace linux
+}  // namespace nearby
+
+#endif  // PLATFORM_IMPL_LINUX_OUTPUT_FILE_H_