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+<!---
+  Licensed to the Apache Software Foundation (ASF) under one
+  or more contributor license agreements.  See the NOTICE file
+  distributed with this work for additional information
+  regarding copyright ownership.  The ASF licenses this file
+  to you 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
+
+    http://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.
+-->
+
+# Red Arrow CUDA - Apache Arrow CUDA Ruby
+
+Red Arrow CUDA is the Ruby bindings of Apache Arrow CUDA. Red Arrow CUDA is based on GObject Introspection.
+
+[Apache Arrow CUDA](https://arrow.apache.org/) is an in-memory columnar data store on GPU.
+
+[GObject Introspection](https://wiki.gnome.org/action/show/Projects/GObjectIntrospection) is a middleware for language bindings of C library. GObject Introspection can generate language bindings automatically at runtime.
+
+Red Arrow CUDA uses [Apache Arrow CUDA GLib](https://github.com/apache/arrow/tree/master/c_glib) and [gobject-introspection gem](https://rubygems.org/gems/gobject-introspection) to generate Ruby bindings of Apache Arrow CUDA.
+
+Apache Arrow CUDA GLib is a C wrapper for [Apache Arrow CUDA C++](https://github.com/apache/arrow/tree/master/cpp). GObject Introspection can't use Apache Arrow CUDA C++ directly. Apache Arrow CUDA GLib is a bridge between Apache Arrow CUDA C++ and GObject Introspection.
+
+gobject-introspection gem is a Ruby bindings of GObject Introspection. Red Arrow CUDA uses GObject Introspection via gobject-introspection gem.
+
+## Install
+
+Install Apache Arrow CUDA GLib before install Red Arrow CUDA. Install Apache Arrow GLib before install Red Arrow. See [Apache Arrow install document](https://arrow.apache.org/install/) for details.
+
+Install Red Arrow CUDA after you install Apache Arrow CUDA GLib:
+
+```text
+% gem install red-arrow-cuda
+```
+
+## Usage
+
+```ruby
+require "arrow-cuda"
+
+manager = ArrowCUDA::DeviceManager.new
+if manager.n_devices.zero?
+  raise "No GPU is found"
+end
+
+context = manager[0]
+buffer = ArrowCUDA::Buffer.new(context, 128)
+ArrowCUDA::BufferOutputStream.open(buffer) do |stream|
+  stream.write("Hello World")
+end
+puts buffer.copy_to_host(0, 11) # => "Hello World"
+```