hbase-server/src/main/java/org/apache/hadoop/hbase/util/CollectionBackedScanner.java

   1 /*
   2  *
   3  * Licensed to the Apache Software Foundation (ASF) under one
   4  * or more contributor license agreements.  See the NOTICE file
   5  * distributed with this work for additional information
   6  * regarding copyright ownership.  The ASF licenses this file
   7  * to you under the Apache License, Version 2.0 (the
   8  * "License"); you may not use this file except in compliance
   9  * with the License.  You may obtain a copy of the License at
  10  *
  11  *     http://www.apache.org/licenses/LICENSE-2.0
  12  *
  13  * Unless required by applicable law or agreed to in writing, software
  14  * distributed under the License is distributed on an "AS IS" BASIS,
  15  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  16  * See the License for the specific language governing permissions and
  17  * limitations under the License.
  18  */
  19 package org.apache.hadoop.hbase.util;
  20
  21 import java.util.ArrayList;
  22 import java.util.Collections;
  23 import java.util.Iterator;
  24 import java.util.List;
  25 import java.util.SortedSet;
  26
  27 import org.apache.yetus.audience.InterfaceAudience;
  28 import org.apache.hadoop.hbase.Cell;
  29 import org.apache.hadoop.hbase.CellComparator;
  30 import org.apache.hadoop.hbase.regionserver.NonReversedNonLazyKeyValueScanner;
  31
  32 /**
  33  * Utility scanner that wraps a sortable collection and serves as a KeyValueScanner.
  34  */
  35 @InterfaceAudience.Private
  36 public class CollectionBackedScanner extends NonReversedNonLazyKeyValueScanner {
  37   final private Iterable<Cell> data;
  38   final CellComparator comparator;
  39   private Iterator<Cell> iter;
  40   private Cell current;
  41
  42   public CollectionBackedScanner(SortedSet<Cell> set) {
  43     this(set, CellComparator.getInstance());
  44   }
  45
  46   public CollectionBackedScanner(SortedSet<Cell> set,
  47       CellComparator comparator) {
  48     this.comparator = comparator;
  49     data = set;
  50     init();
  51   }
  52
  53   public CollectionBackedScanner(List<Cell> list) {
  54     this(list, CellComparator.getInstance());
  55   }
  56
  57   public CollectionBackedScanner(List<Cell> list,
  58       CellComparator comparator) {
  59     Collections.sort(list, comparator);
  60     this.comparator = comparator;
  61     data = list;
  62     init();
  63   }
  64
  65   public CollectionBackedScanner(CellComparator comparator,
  66       Cell... array) {
  67     this.comparator = comparator;
  68
  69     List<Cell> tmp = new ArrayList<>(array.length);
  70     Collections.addAll(tmp, array);
  71     Collections.sort(tmp, comparator);
  72     data = tmp;
  73     init();
  74   }
  75
  76   private void init() {
  77     iter = data.iterator();
  78     if(iter.hasNext()){
  79       current = iter.next();
  80     }
  81   }
  82
  83   @Override
  84   public Cell peek() {
  85     return current;
  86   }
  87
  88   @Override
  89   public Cell next() {
  90     Cell oldCurrent = current;
  91     if(iter.hasNext()){
  92       current = iter.next();
  93     } else {
  94       current = null;
  95     }
  96     return oldCurrent;
  97   }
  98
  99   @Override
 100   public boolean seek(Cell seekCell) {
 101     // restart iterator
 102     iter = data.iterator();
 103     return reseek(seekCell);
 104   }
 105
 106   @Override
 107   public boolean reseek(Cell seekCell) {
 108     while(iter.hasNext()){
 109       Cell next = iter.next();
 110       int ret = comparator.compare(next, seekCell);
 111       if(ret >= 0){
 112         current = next;
 113         return true;
 114       }
 115     }
 116     return false;
 117   }
 118
 119
 120   @Override
 121   public void close() {
 122     // do nothing
 123   }
 124 }