streaming/src/main/java/org/apache/gearpump/streaming/refactor/coder/StringUtf8Coder.java

/*
 * 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.
 */

package org.apache.gearpump.streaming.refactor.coder;

import com.google.common.base.Utf8;

import java.io.*;
import java.nio.charset.StandardCharsets;

public class StringUtf8Coder extends AtomicCoder<String> {

    public static StringUtf8Coder of() {
        return INSTANCE;
    }

    /////////////////////////////////////////////////////////////////////////////

    private static final StringUtf8Coder INSTANCE = new StringUtf8Coder();

    private static void writeString(String value, DataOutputStream dos)
            throws IOException {
        byte[] bytes = value.getBytes(StandardCharsets.UTF_8);
        VarInt.encode(bytes.length, dos);
        dos.write(bytes);
    }

    private static String readString(DataInputStream dis) throws IOException {
        int len = VarInt.decodeInt(dis);
        if (len < 0) {
            throw new CoderException("Invalid encoded string length: " + len);
        }
        byte[] bytes = new byte[len];
        dis.readFully(bytes);
        return new String(bytes, StandardCharsets.UTF_8);
    }

    private StringUtf8Coder() {
    }

    @Override
    public void encode(String value, OutputStream outStream) throws CoderException {
        if (value == null) {
            throw new CoderException("cannot encode a null String");
        }
        try {
            writeString(value, new DataOutputStream(outStream));
        } catch (IOException e) {
            throw new CoderException(e);
        }
    }

    @Override
    public String decode(InputStream inStream)
            throws CoderException {
        try {
            return readString(new DataInputStream(inStream));
        } catch (EOFException | UTFDataFormatException exn) {
            // These exceptions correspond to decoding problems, so change
            // what kind of exception they're branded as.
            throw new CoderException(exn);
        } catch (Exception e) {
            throw new CoderException(e);
        }
    }

    @Override
    public void verifyDeterministic() {
    }

    @Override
    public boolean consistentWithEquals() {
        return true;
    }

    @Override
    public long getEncodedElementByteSize(String value) {
        if (value == null) {
            throw new CoderException("cannot encode a null String");
        }
        int size = Utf8.encodedLength(value);
        return VarInt.getLength(size) + size;
    }
}