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/*
* 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.spark.util.collection.unsafe.sort;
import com.google.common.primitives.UnsignedLongs;
import org.apache.spark.annotation.Private;
import org.apache.spark.unsafe.types.ByteArray;
import org.apache.spark.unsafe.types.UTF8String;
@Private
public class PrefixComparators {
private PrefixComparators() {}
public static final PrefixComparator STRING = new UnsignedPrefixComparator();
public static final PrefixComparator STRING_DESC = new UnsignedPrefixComparatorDesc();
public static final PrefixComparator BINARY = new UnsignedPrefixComparator();
public static final PrefixComparator BINARY_DESC = new UnsignedPrefixComparatorDesc();
public static final PrefixComparator LONG = new SignedPrefixComparator();
public static final PrefixComparator LONG_DESC = new SignedPrefixComparatorDesc();
public static final PrefixComparator DOUBLE = new UnsignedPrefixComparator();
public static final PrefixComparator DOUBLE_DESC = new UnsignedPrefixComparatorDesc();
public static final class StringPrefixComparator {
public static long computePrefix(UTF8String value) {
return value == null ? 0L : value.getPrefix();
}
}
public static final class BinaryPrefixComparator {
public static long computePrefix(byte[] bytes) {
return ByteArray.getPrefix(bytes);
}
}
public static final class DoublePrefixComparator {
/**
* Converts the double into a value that compares correctly as an unsigned long. For more
* details see http://stereopsis.com/radix.html.
*/
public static long computePrefix(double value) {
// Java's doubleToLongBits already canonicalizes all NaN values to the smallest possible
// positive NaN, so there's nothing special we need to do for NaNs.
long bits = Double.doubleToLongBits(value);
// Negative floats compare backwards due to their sign-magnitude representation, so flip
// all the bits in this case.
long mask = -(bits >>> 63) | 0x8000000000000000L;
return bits ^ mask;
}
}
/**
* Provides radix sort parameters. Comparators implementing this also are indicating that the
* ordering they define is compatible with radix sort.
*/
public abstract static class RadixSortSupport extends PrefixComparator {
/** @return Whether the sort should be descending in binary sort order. */
public abstract boolean sortDescending();
/** @return Whether the sort should take into account the sign bit. */
public abstract boolean sortSigned();
}
//
// Standard prefix comparator implementations
//
public static final class UnsignedPrefixComparator extends RadixSortSupport {
@Override public boolean sortDescending() { return false; }
@Override public boolean sortSigned() { return false; }
@Override
public int compare(long aPrefix, long bPrefix) {
return UnsignedLongs.compare(aPrefix, bPrefix);
}
}
public static final class UnsignedPrefixComparatorDesc extends RadixSortSupport {
@Override public boolean sortDescending() { return true; }
@Override public boolean sortSigned() { return false; }
@Override
public int compare(long bPrefix, long aPrefix) {
return UnsignedLongs.compare(aPrefix, bPrefix);
}
}
public static final class SignedPrefixComparator extends RadixSortSupport {
@Override public boolean sortDescending() { return false; }
@Override public boolean sortSigned() { return true; }
@Override
public int compare(long a, long b) {
return (a < b) ? -1 : (a > b) ? 1 : 0;
}
}
public static final class SignedPrefixComparatorDesc extends RadixSortSupport {
@Override public boolean sortDescending() { return true; }
@Override public boolean sortSigned() { return true; }
@Override
public int compare(long b, long a) {
return (a < b) ? -1 : (a > b) ? 1 : 0;
}
}
}
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