| 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.IndexInput; |
| |
| import java.io.IOException; |
| |
| final class PackedReaderIterator implements PackedInts.ReaderIterator { |
| private long pending; |
| private int pendingBitsLeft; |
| private final IndexInput in; |
| private final int bitsPerValue; |
| private final int valueCount; |
| private int position = -1; |
| |
| // masks[n-1] masks for bottom n bits |
| private final long[] masks; |
| |
| public PackedReaderIterator(int bitsPerValue, int valueCount, IndexInput in) |
| throws IOException { |
| |
| this.valueCount = valueCount; |
| this.bitsPerValue = bitsPerValue; |
| |
| this.in = in; |
| masks = new long[bitsPerValue]; |
| |
| long v = 1; |
| for (int i = 0; i < bitsPerValue; i++) { |
| v *= 2; |
| masks[i] = v - 1; |
| } |
| } |
| |
| public int getBitsPerValue() { |
| return bitsPerValue; |
| } |
| |
| public int size() { |
| return valueCount; |
| } |
| |
| public long next() throws IOException { |
| if (pendingBitsLeft == 0) { |
| pending = in.readLong(); |
| pendingBitsLeft = 64; |
| } |
| |
| final long result; |
| if (pendingBitsLeft >= bitsPerValue) { // not split |
| result = (pending >> (pendingBitsLeft - bitsPerValue)) & masks[bitsPerValue-1]; |
| pendingBitsLeft -= bitsPerValue; |
| } else { // split |
| final int bits1 = bitsPerValue - pendingBitsLeft; |
| final long result1 = (pending & masks[pendingBitsLeft-1]) << bits1; |
| pending = in.readLong(); |
| final long result2 = (pending >> (64 - bits1)) & masks[bits1-1]; |
| pendingBitsLeft = 64 + pendingBitsLeft - bitsPerValue; |
| result = result1 | result2; |
| } |
| |
| ++position; |
| return result; |
| } |
| |
| public void close() throws IOException { |
| in.close(); |
| } |
| |
| public int ord() { |
| return position; |
| } |
| |
| public long advance(final int ord) throws IOException{ |
| assert ord < valueCount : "ord must be less than valueCount"; |
| assert ord > position : "ord must be greater than the current position"; |
| final long bits = (long) bitsPerValue; |
| final int posToSkip = ord - 1 - position; |
| final long bitsToSkip = (bits * (long)posToSkip); |
| if (bitsToSkip < pendingBitsLeft) { // enough bits left - no seek required |
| pendingBitsLeft -= bitsToSkip; |
| } else { |
| final long skip = bitsToSkip-pendingBitsLeft; |
| final long closestByte = (skip >> 6) << 3; |
| if (closestByte != 0) { // need to seek |
| final long filePointer = in.getFilePointer(); |
| in.seek(filePointer + closestByte); |
| } |
| pending = in.readLong(); |
| pendingBitsLeft = 64 - (int)(skip % 64); |
| } |
| position = ord-1; |
| return next(); |
| } |
| } |