content: package org.apache.lucene.util.fst;
  
  /**
   * 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.
   */
  
  import java.io.IOException;
  
  import org.apache.lucene.store.DataInput;
  import org.apache.lucene.store.DataOutput;
  import org.apache.lucene.util.BytesRef;
  
  /**
   * Output is a sequence of bytes, for each input term.
   *
   * @lucene.experimental
   */
  
  public final class ByteSequenceOutputs extends Outputs<BytesRef> {
  
    private final static BytesRef NO_OUTPUT = new BytesRef();
  
    private ByteSequenceOutputs() {
    }
  
    public static ByteSequenceOutputs getSingleton() {
      return new ByteSequenceOutputs();
    }
  
    @Override
    public BytesRef common(BytesRef output1, BytesRef output2) {
      assert output1 != null;
      assert output2 != null;
  
      int pos1 = output1.offset;
      int pos2 = output2.offset;
      int stopAt1 = pos1 + Math.min(output1.length, output2.length);
      while(pos1 < stopAt1) {
        if (output1.bytes[pos1] != output2.bytes[pos2]) {
          break;
        }
        pos1++;
        pos2++;
      }
  
      if (pos1 == output1.offset) {
        // no common prefix
        return NO_OUTPUT;
      } else if (pos1 == output1.offset + output1.length) {
        // output1 is a prefix of output2
        return output1;
      } else if (pos2 == output2.offset + output2.length) {
        // output2 is a prefix of output1
        return output2;
      } else {
        return new BytesRef(output1.bytes, output1.offset, pos1-output1.offset);
      }
    }
  
    @Override
    public BytesRef subtract(BytesRef output, BytesRef inc) {
      assert output != null;
      assert inc != null;
      if (inc == NO_OUTPUT) {
        // no prefix removed
        return output;
      } else if (inc.length == output.length) {
        // entire output removed
        return NO_OUTPUT;
      } else {
        assert inc.length < output.length: "inc.length=" + inc.length + " vs output.length=" + output.length;
        assert inc.length > 0;
        return new BytesRef(output.bytes, output.offset + inc.length, output.length-inc.length);
      }
    }
  
    @Override
    public BytesRef add(BytesRef prefix, BytesRef output) {
      assert prefix != null;
      assert output != null;
      if (prefix == NO_OUTPUT) {
        return output;
      } else if (output == NO_OUTPUT) {
        return prefix;
      } else {
        assert prefix.length > 0;
        assert output.length > 0;
        BytesRef result = new BytesRef(prefix.length + output.length);
        System.arraycopy(prefix.bytes, prefix.offset, result.bytes, 0, prefix.length);
        System.arraycopy(output.bytes, output.offset, result.bytes, prefix.length, output.length);
        result.length = prefix.length + output.length;
        return result;
      }
    }
  
    @Override
    public void write(BytesRef prefix, DataOutput out) throws IOException {
      assert prefix != null;
      out.writeVInt(prefix.length);
      out.writeBytes(prefix.bytes, prefix.offset, prefix.length);
    }
  
    @Override
    public BytesRef read(DataInput in) throws IOException {
      final int len = in.readVInt();
      if (len == 0) {
        return NO_OUTPUT;
      } else {
        final BytesRef output = new BytesRef(len);
        in.readBytes(output.bytes, 0, len);
        output.length = len;
        return output;
      }
    }
  
    @Override
    public BytesRef getNoOutput() {
      return NO_OUTPUT;
    }
  
    @Override
    public String outputToString(BytesRef output) {
      return output.utf8ToString();
    }
  }
  