MessagingSerializers.java

package io.datakernel.stream.net;

import com.google.gson.Gson;
import com.google.gson.JsonSyntaxException;
import io.datakernel.bytebuf.ByteBuf;
import io.datakernel.bytebuf.ByteBufPool;
import io.datakernel.bytebuf.ByteBufStrings;
import io.datakernel.exception.ParseException;

import static io.datakernel.bytebuf.ByteBufStrings.putUtf8;

@SuppressWarnings("ThrowableInstanceNeverThrown, WeakerAccess")
public final class MessagingSerializers {
	public static final ParseException DESERIALIZE_ERR = new ParseException("Can't deserialize message");

	private MessagingSerializers() {
	}

	public static <I, O> MessagingSerializer<I, O> ofGson(final Gson in, final Class<I> inputClass,
	                                                      final Gson out, final Class<O> outputClass) {
		return new MessagingSerializer<I, O>() {
			@Override
			public I tryDeserialize(ByteBuf buf) throws ParseException {
				for (int len = 0; len < buf.readRemaining(); len++) {
					if (buf.peek(len) == '\0') {
						try {
							I item = in.fromJson(ByteBufStrings.decodeUtf8(buf.array(), buf.readPosition(), len), inputClass);
							buf.moveReadPosition(len + 1); // skipping msg + delimiter
							return item;
						} catch (JsonSyntaxException e) {
							throw DESERIALIZE_ERR;
						}
					}
				}
				return null;
			}

			@Override
			public ByteBuf serialize(O item) {
				ByteBufPoolAppendable appendable = new ByteBufPoolAppendable();
				out.toJson(item, outputClass, appendable);
				appendable.append("\0");
				return appendable.get();
			}
		};
	}

	static class ByteBufPoolAppendable implements Appendable {
		static final int INITIAL_BUF_SIZE = 2 * 1024;
		ByteBuf container;

		ByteBufPoolAppendable() {this(INITIAL_BUF_SIZE);}

		ByteBufPoolAppendable(int size) {
			this.container = ByteBufPool.allocate(size);
		}

		@Override
		public Appendable append(CharSequence csq) {
			container = ByteBufPool.ensureTailRemaining(container, csq.length() * 3);
			for (int i = 0; i < csq.length(); i++) {
				putUtf8(container, csq.charAt(i));
			}
			return this;
		}

		@Override
		public Appendable append(CharSequence csq, int start, int end) {
			return append(csq.subSequence(start, end));
		}

		@Override
		public Appendable append(char c) {
			container = ByteBufPool.ensureTailRemaining(container, 3);
			putUtf8(container, c);
			return this;
		}

		public ByteBuf get() {
			return container;
		}
	}
}