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
   *
   *     https://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.trevni;
  
  import java.io.IOException;
  
  import java.util.Arrays;
  
  class ColumnDescriptor<T extends Comparable> {
    final Input file;
    final ColumnMetaData metaData;
  
    long start;
    long dataStart;
  
    BlockDescriptor[] blocks;
  
    long[] blockStarts; // for random access
    long[] firstRows; // for binary searches
    T[] firstValues; // for binary searches
  
    public ColumnDescriptor(Input file, ColumnMetaData metaData) {
      this.file = file;
      this.metaData = metaData;
    }
  
    public int findBlock(long row) {
      int block = Arrays.binarySearch(firstRows, row);
      if (block < 0)
        block = -block - 2;
      return block;
    }
  
    public int findBlock(T value) {
      int block = Arrays.binarySearch(firstValues, value);
      if (block < 0)
        block = -block - 2;
      return block;
    }
  
    public int blockCount() {
      return blocks.length;
    }
  
    public long lastRow(int block) {
      if (blocks.length == 0 || block < 0)
        return 0;
      return firstRows[block] + blocks[block].rowCount;
    }
  
    public void ensureBlocksRead() throws IOException {
      if (blocks != null)
        return;
  
      // read block descriptors
      InputBuffer in = new InputBuffer(file, start);
      int blockCount = in.readFixed32();
      BlockDescriptor[] blocks = new BlockDescriptor[blockCount];
      if (metaData.hasIndexValues())
        firstValues = (T[]) new Comparable[blockCount];
  
      for (int i = 0; i < blockCount; i++) {
        blocks[i] = BlockDescriptor.read(in);
        if (metaData.hasIndexValues())
          firstValues[i] = in.readValue(metaData.getType());
      }
      dataStart = in.tell();
  
      // compute blockStarts and firstRows
      Checksum checksum = Checksum.get(metaData);
      blockStarts = new long[blocks.length];
      firstRows = new long[blocks.length];
      long startPosition = dataStart;
      long row = 0;
      for (int i = 0; i < blockCount; i++) {
        BlockDescriptor b = blocks[i];
        blockStarts[i] = startPosition;
        firstRows[i] = row;
        startPosition += b.compressedSize + checksum.size();
        row += b.rowCount;
      }
      this.blocks = blocks;
    }
  
  }
  