Static utility methods to read/write collections to/from a byte stream, using protostuff.

CollectionSerializationUtils.java

package com.foo.serialization;

import com.dyuproject.protostuff.LinkedBuffer;
import com.dyuproject.protostuff.ProtostuffIOUtil;
import com.dyuproject.protostuff.Schema;
import com.google.common.collect.Lists;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.List;

/**
 * Static utility methods to read/write collections to/from a byte stream, using protostuff.
 */
public final class CollectionSerializationUtils {

    private CollectionSerializationUtils() { /* prevents instantiation */ }

    public static <T> void writeListTo(OutputStream out, List<T> messages, Schema<T> schema) throws IOException {
        writeSize(out, messages);
        writeMessages(out, messages, schema);
    }

    public static <T> List<T> parseListFrom(InputStream in, Schema<T> schema) throws IOException {
        int size = readSize(in);
        return readMessages(in, schema, size);
    }

    private static <T> void writeSize(OutputStream out, List<T> messages) throws IOException {
        out.write(messages.size());
    }

    private static int readSize(InputStream in) throws IOException {
        return in.read();
    }

    private static <T> void writeMessages(OutputStream out, List<T> messages, Schema<T> schema) throws IOException {
        LinkedBuffer buffer = LinkedBuffer.allocate(LinkedBuffer.DEFAULT_BUFFER_SIZE);
        for (T message : messages) {
            ProtostuffIOUtil.writeDelimitedTo(out, message, schema, buffer);
            buffer.clear();
        }
    }

    private static <T> List<T> readMessages(InputStream in, Schema<T> schema, int size) throws IOException {
        List<T> messages = Lists.newArrayListWithCapacity(size);

        LinkedBuffer buffer = LinkedBuffer.allocate(LinkedBuffer.DEFAULT_BUFFER_SIZE);
        for (int i = 0; i < size; i++) {
            T message = schema.newMessage();
            ProtostuffIOUtil.mergeDelimitedFrom(in, message, schema, buffer);
            messages.add(message);
            buffer.clear();
        }
        return messages;
    }

}