/*
* 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.
*/
package org.apache.lucene.util.packed;
import java.io.IOException;
import org.apache.lucene.store.DataInput;
/**
* A {@link DataInput} wrapper to read unaligned, variable-length packed
* integers. This API is much slower than the {@link PackedInts} fixed-length
* API but can be convenient to save space.
* @see PackedDataOutput
* @lucene.internal
*/
public final class PackedDataInput {
final DataInput in;
long current;
int remainingBits;
/**
* Create a new instance that wraps <code>in</code>.
*/
public PackedDataInput(DataInput in) {
this.in = in;
skipToNextByte();
}
/**
* Read the next long using exactly <code>bitsPerValue</code> bits.
*/
public long readLong(int bitsPerValue) throws IOException {
assert bitsPerValue > 0 && bitsPerValue <= 64 : bitsPerValue;
long r = 0;
while (bitsPerValue > 0) {
if (remainingBits == 0) {
current = in.readByte() & 0xFF;
remainingBits = 8;
}
final int bits = Math.min(bitsPerValue, remainingBits);
r = (r << bits) | ((current >>> (remainingBits - bits)) & ((1L << bits) - 1));
bitsPerValue -= bits;
remainingBits -= bits;
}
return r;
}
/**
* If there are pending bits (at most 7), they will be ignored and the next
* value will be read starting at the next byte.
*/
public void skipToNextByte() {
remainingBits = 0;
}
}