content: /*
   * 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.beam.sdk.coders;
  
  import java.io.EOFException;
  import java.io.IOException;
  import java.io.InputStream;
  import java.io.OutputStream;
  import java.io.UTFDataFormatException;
  import java.nio.charset.StandardCharsets;
  import org.apache.beam.sdk.util.ExposedByteArrayOutputStream;
  import org.apache.beam.sdk.util.StreamUtils;
  import org.apache.beam.sdk.util.VarInt;
  import org.apache.beam.sdk.values.TypeDescriptor;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Utf8;
  import org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.io.ByteStreams;
  
  /**
   * A {@link Coder} that encodes {@link String Strings} in UTF-8 encoding. If in a nested context,
   * prefixes the string with an integer length field, encoded via a {@link VarIntCoder}.
   */
  public class StringUtf8Coder extends AtomicCoder<String> {
  
    public static StringUtf8Coder of() {
      return INSTANCE;
    }
  
    /////////////////////////////////////////////////////////////////////////////
  
    private static final StringUtf8Coder INSTANCE = new StringUtf8Coder();
    private static final TypeDescriptor<String> TYPE_DESCRIPTOR = new TypeDescriptor<String>() {};
  
    private static void writeString(String value, OutputStream dos) throws IOException {
      byte[] bytes = value.getBytes(StandardCharsets.UTF_8);
      VarInt.encode(bytes.length, dos);
      dos.write(bytes);
    }
  
    private static String readString(InputStream dis) throws IOException {
      int len = VarInt.decodeInt(dis);
      if (len < 0) {
        throw new CoderException("Invalid encoded string length: " + len);
      }
      byte[] bytes = new byte[len];
      ByteStreams.readFully(dis, bytes);
      return new String(bytes, StandardCharsets.UTF_8);
    }
  
    private StringUtf8Coder() {}
  
    @Override
    public void encode(String value, OutputStream outStream) throws IOException {
      encode(value, outStream, Context.NESTED);
    }
  
    @Override
    public void encode(String value, OutputStream outStream, Context context) throws IOException {
      if (value == null) {
        throw new CoderException("cannot encode a null String");
      }
      if (context.isWholeStream) {
        byte[] bytes = value.getBytes(StandardCharsets.UTF_8);
        if (outStream instanceof ExposedByteArrayOutputStream) {
          ((ExposedByteArrayOutputStream) outStream).writeAndOwn(bytes);
        } else {
          outStream.write(bytes);
        }
      } else {
        writeString(value, outStream);
      }
    }
  
    @Override
    public String decode(InputStream inStream) throws IOException {
      return decode(inStream, Context.NESTED);
    }
  
    @Override
    public String decode(InputStream inStream, Context context) throws IOException {
      if (context.isWholeStream) {
        byte[] bytes = StreamUtils.getBytesWithoutClosing(inStream);
        return new String(bytes, StandardCharsets.UTF_8);
      } else {
        try {
          return readString(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);
        }
      }
    }
  
    @Override
    public void verifyDeterministic() {}
  
    /**
     * {@inheritDoc}
     *
     * @return {@code true}. This coder is injective.
     */
    @Override
    public boolean consistentWithEquals() {
      return true;
    }
  
    @Override
    public TypeDescriptor<String> getEncodedTypeDescriptor() {
      return TYPE_DESCRIPTOR;
    }
  
    /**
     * {@inheritDoc}
     *
     * @return the byte size of the UTF-8 encoding of the string or, in a nested context, the byte
     *     size of the encoding plus the encoded length prefix.
     */
    @Override
    public long getEncodedElementByteSize(String value) throws Exception {
      if (value == null) {
        throw new CoderException("cannot encode a null String");
      }
      int size = Utf8.encodedLength(value);
      return (long) VarInt.getLength(size) + size;
    }
  }
  