Implementing a Writeable for Protobuf

Signed-off-by: Vacha Shah <[email protected]>

server/build.gradle

@@ -115,6 +115,7 @@ dependencies {
   // utilities
   api project(":libs:opensearch-cli")
   api 'com.carrotsearch:hppc:0.8.1'
+  api 'com.google.protobuf:protobuf-java:3.22.2'
 
   // time handling, remove with java 8 time
   api "joda-time:joda-time:${versions.joda}"

server/src/main/java/org/opensearch/common/io/stream/BaseWriteable.java

@@ -0,0 +1,53 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.common.io.stream;
+
+import java.io.IOException;
+
+/**
+ * This interface can be extended to different types of serialization and deserialization mechanisms.
+ *
+ * @opensearch.internal
+ */
+public interface BaseWriteable<T, S> {
+
+    /**
+     * Write this into the stream output.
+    */
+    void writeTo(T out) throws IOException;
+
+    /**
+     * Reference to a method that can write some object to a given type.
+     */
+    @FunctionalInterface
+    interface Writer<T, V> {
+
+        /**
+         * Write {@code V}-type {@code value} to the {@code T}-type stream.
+         *
+         * @param out Output to write the {@code value} too
+         * @param value The value to add
+         */
+        void write(T out, V value) throws IOException;
+    }
+
+    /**
+     * Reference to a method that can read some object from a given stream type.
+     */
+    @FunctionalInterface
+    interface Reader<S, V> {
+
+        /**
+         * Read {@code V}-type value from a {@code T}-type stream.
+        *
+        * @param in Input to read the value from
+        */
+        V read(S in) throws IOException;
+    }
+}

server/src/main/java/org/opensearch/common/io/stream/ProtobufWriteable.java

@@ -0,0 +1,76 @@
+/*
+* SPDX-License-Identifier: Apache-2.0
+*
+* The OpenSearch Contributors require contributions made to
+* this file be licensed under the Apache-2.0 license or a
+* compatible open source license.
+*/
+
+/*
+* Modifications Copyright OpenSearch Contributors. See
+* GitHub history for details.
+*/
+
+package org.opensearch.common.io.stream;
+
+import java.io.IOException;
+import com.google.protobuf.CodedInputStream;
+import com.google.protobuf.CodedOutputStream;
+
+/**
+ * Implementers can be written to write to output and read from input using Protobuf.
+*
+* @opensearch.internal
+*/
+public interface ProtobufWriteable extends BaseWriteable<com.google.protobuf.CodedOutputStream, com.google.protobuf.CodedInputStream> {
+
+    /**
+     * Write this into the stream output.
+    */
+    public abstract void writeTo(com.google.protobuf.CodedOutputStream out) throws IOException;
+
+    /**
+     * Reference to a method that can write some object to a {@link com.google.protobuf.CodedOutputStream}.
+     * Most classes should implement {@link ProtobufWriteable} and the {@link ProtobufWriteable#writeTo(CodedOutputStream)} method should <em>use</em>
+     * {@link CodedOutputStream} methods directly or this indirectly:
+     * <pre><code>
+     * public void writeTo(CodedOutputStream out) throws IOException {
+     *     out.writeVInt(someValue);
+     * }
+     * </code></pre>
+     */
+    @FunctionalInterface
+    interface Writer<V> {
+
+        /**
+         * Write {@code V}-type {@code value} to the {@code out}put stream.
+        *
+        * @param out Output to write the {@code value} too
+        * @param value The value to add
+        */
+        void write(com.google.protobuf.CodedOutputStream out, V value) throws IOException;
+
+    }
+
+    /**
+     * Reference to a method that can read some object from a stream. By convention this is a constructor that takes
+     * {@linkplain com.google.protobuf.CodedInputStream} as an argument for most classes and a static method for things like enums.
+     * <pre><code>
+     * public MyClass(final CodedInputStream in) throws IOException {
+     *     this.someValue = in.readVInt();
+     * }
+     * </code></pre>
+     */
+    @FunctionalInterface
+    interface Reader<V> {
+
+        /**
+         * Read {@code V}-type value from a stream.
+        *
+        * @param in Input to read the value from
+        */
+        V read(com.google.protobuf.CodedInputStream in) throws IOException;
+
+    }
+
+}