| 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 java.io.IOException; |
| |
| import org.apache.lucene.store.IndexInput; |
| |
| /* Reads directly from disk on each get */ |
| class DirectPackedReader extends PackedInts.ReaderImpl { |
| private final long startPointer; |
| private final ThreadLocal<IndexInput> in; |
| |
| public DirectPackedReader(int bitsPerValue, int valueCount, IndexInput input) { |
| super(valueCount, bitsPerValue); |
| this.in = new ThreadLocal<IndexInput>() { |
| @Override |
| protected IndexInput initialValue() { |
| return input.clone(); |
| } |
| }; |
| startPointer = input.getFilePointer(); |
| } |
| |
| @Override |
| public long get(int index) { |
| final long majorBitPos = (long)index * bitsPerValue; |
| final long elementPos = majorBitPos >>> 3; |
| try { |
| IndexInput indexInput = in.get(); |
| indexInput .seek(startPointer + elementPos); |
| |
| final byte b0 = indexInput.readByte(); |
| final int bitPos = (int) (majorBitPos & 7); |
| if (bitPos + bitsPerValue <= 8) { |
| // special case: all bits are in the first byte |
| return (b0 & ((1L << (8 - bitPos)) - 1)) >>> (8 - bitPos - bitsPerValue); |
| } |
| |
| // take bits from the first byte |
| int remainingBits = bitsPerValue - 8 + bitPos; |
| long result = (b0 & ((1L << (8 - bitPos)) - 1)) << remainingBits; |
| |
| // add bits from inner bytes |
| while (remainingBits >= 8) { |
| remainingBits -= 8; |
| result |= (indexInput.readByte() & 0xFFL) << remainingBits; |
| } |
| |
| // take bits from the last byte |
| if (remainingBits > 0) { |
| result |= (indexInput.readByte() & 0xFFL) >>> (8 - remainingBits); |
| } |
| |
| return result; |
| } catch (IOException ioe) { |
| throw new IllegalStateException("failed", ioe); |
| } |
| } |
| |
| @Override |
| public long ramBytesUsed() { |
| return 0; |
| } |
| } |