content: package org.apache.lucene.util.packed;
  
  /**
   * 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 org.apache.lucene.store.DataOutput;
  
  import java.io.IOException;
  
  // Packs high order byte first, to match
  // IndexOutput.writeInt/Long/Short byte order
  
  /**
   * Generic writer for space-optimal packed values. The resulting bits can be
   * used directly by Packed32, Packed64 and PackedDirect* and will always be
   * long-aligned.
   */
  
  class PackedWriter extends PackedInts.Writer {
    private long pending;
    private int pendingBitPos;
  
    // masks[n-1] masks for bottom n bits
    private final long[] masks;
    private int written = 0;
  
    public PackedWriter(DataOutput out, int valueCount, int bitsPerValue)
                                                              throws IOException {
      super(out, valueCount, bitsPerValue);
  
      pendingBitPos = 64;
      masks = new long[bitsPerValue - 1];
  
      long v = 1;
      for (int i = 0; i < bitsPerValue - 1; i++) {
        v *= 2;
        masks[i] = v - 1;
      }
    }
  
    /**
     * Do not call this after finish
     */
    @Override
    public void add(long v) throws IOException {
      assert v <= PackedInts.maxValue(bitsPerValue) : "v=" + v
              + " maxValue=" + PackedInts.maxValue(bitsPerValue);
      assert v >= 0;
      //System.out.println("    packedw add v=" + v + " pendingBitPos=" + pendingBitPos);
  
      // TODO
      if (pendingBitPos >= bitsPerValue) {
        // not split
  
        // write-once, so we can |= w/o first masking to 0s
        pending |= v << (pendingBitPos - bitsPerValue);
        if (pendingBitPos == bitsPerValue) {
          // flush
          out.writeLong(pending);
          pending = 0;
          pendingBitPos = 64;
        } else {
          pendingBitPos -= bitsPerValue;
        }
  
      } else {
        // split
  
        // write top pendingBitPos bits of value into bottom bits of pending
        pending |= (v >> (bitsPerValue - pendingBitPos)) & masks[pendingBitPos - 1];
        //System.out.println("      part1 (v >> " + (bitsPerValue - pendingBitPos) + ") & " + masks[pendingBitPos-1]);
  
        // flush
        out.writeLong(pending);
  
        // write bottom (bitsPerValue - pendingBitPos) bits of value into top bits of pending
        pendingBitPos = 64 - bitsPerValue + pendingBitPos;
        //System.out.println("      part2 v << " + pendingBitPos);
        pending = (v << pendingBitPos);
      }
      written++;
    }
  
    @Override
    public void finish() throws IOException {
      while (written < valueCount) {
        add(0L); // Auto flush
      }
  
      if (pendingBitPos != 64) {
        out.writeLong(pending);
      }
    }
  
    @Override
    public String toString() {
      return "PackedWriter(written " + written + "/" + valueCount + " with "
              + bitsPerValue + " bits/value)";
    }
  }
  