/**
* 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.cassandra.dht;
import java.io.Serializable;
import java.nio.ByteBuffer;
import java.util.*;
import org.apache.cassandra.utils.ByteBufferUtil;
import org.apache.commons.lang.ObjectUtils;
import org.apache.cassandra.service.StorageService;
import org.apache.cassandra.utils.FBUtilities;
/**
* A representation of the range that a node is responsible for on the DHT ring.
*
* A Range is responsible for the tokens between (left, right].
*/
public class Range extends AbstractBounds implements Comparable<Range>, Serializable
{
public static final long serialVersionUID = 1L;
public Range(Token left, Token right)
{
this(left, right, StorageService.getPartitioner());
}
public Range(Token left, Token right, IPartitioner partitioner)
{
super(left, right, partitioner);
}
public static boolean contains(Token left, Token right, Token bi)
{
if (isWrapAround(left, right))
{
/*
* We are wrapping around, so the interval is (a,b] where a >= b,
* then we have 3 cases which hold for any given token k:
* (1) a < k -- return true
* (2) k <= b -- return true
* (3) b < k <= a -- return false
*/
if (bi.compareTo(left) > 0)
return true;
else
return right.compareTo(bi) >= 0;
}
else
{
/*
* This is the range (a, b] where a < b.
*/
return ( compare(bi,left) > 0 && compare(right,bi) >= 0);
}
}
public boolean contains(Range that)
{
if (this.left.equals(this.right))
{
// full ring always contains all other ranges
return true;
}
boolean thiswraps = isWrapAround(left, right);
boolean thatwraps = isWrapAround(that.left, that.right);
if (thiswraps == thatwraps)
{
return compare(left,that.left) <= 0 && compare(that.right,right) <= 0;
}
else if (thiswraps)
{
// wrapping might contain non-wrapping
// that is contained if both its tokens are in one of our wrap segments
return compare(left,that.left) <= 0 || compare(that.right,right) <= 0;
}
else
{
// (thatwraps)
// non-wrapping cannot contain wrapping
return false;
}
}
/**
* Helps determine if a given point on the DHT ring is contained
* in the range in question.
* @param bi point in question
* @return true if the point contains within the range else false.
*/
public boolean contains(Token bi)
{
return contains(left, right, bi);
}
/**
* @param that range to check for intersection
* @return true if the given range intersects with this range.
*/
public boolean intersects(Range that)
{
return intersectionWith(that).size() > 0;
}
public static Set<Range> rangeSet(Range ... ranges)
{
return Collections.unmodifiableSet(new HashSet<Range>(Arrays.asList(ranges)));
}
/**
* @param that
* @return the intersection of the two Ranges. this can be two disjoint Ranges if one is wrapping and one is not.
* say you have nodes G and M, with query range (D,T]; the intersection is (M-T] and (D-G].
* If there is no intersection, an empty list is returned.
*/
public Set<Range> intersectionWith(Range that)
{
if (that.contains(this))
return rangeSet(this);
if (this.contains(that))
return rangeSet(that);
boolean thiswraps = isWrapAround(left, right);
boolean thatwraps = isWrapAround(that.left, that.right);
if (!thiswraps && !thatwraps)
{
// neither wraps. the straightforward case.
if (!(left.compareTo(that.right) < 0 && that.left.compareTo(right) < 0))
return Collections.emptySet();
return rangeSet(new Range((Token)ObjectUtils.max(this.left, that.left),
(Token)ObjectUtils.min(this.right, that.right)));
}
if (thiswraps && thatwraps)
{
// if the starts are the same, one contains the other, which we have already ruled out.
assert !this.left.equals(that.left);
// two wrapping ranges always intersect.
// since we have already determined that neither this nor that contains the other, we have 2 cases,
// and mirror images of those case.
// (1) both of that's (1, 2] endpoints lie in this's (A, B] right segment:
// ---------B--------A--1----2------>
// (2) only that's start endpoint lies in this's right segment:
// ---------B----1---A-------2------>
// or, we have the same cases on the left segement, which we can handle by swapping this and that.
return this.left.compareTo(that.left) < 0
? intersectionBothWrapping(this, that)
: intersectionBothWrapping(that, this);
}
if (thiswraps && !thatwraps)
return intersectionOneWrapping(this, that);
assert (!thiswraps && thatwraps);
return intersectionOneWrapping(that, this);
}
private static Set<Range> intersectionBothWrapping(Range first, Range that)
{
Set<Range> intersection = new HashSet<Range>(2);
if (that.right.compareTo(first.left) > 0)
intersection.add(new Range(first.left, that.right));
intersection.add(new Range(that.left, first.right));
return Collections.unmodifiableSet(intersection);
}
private static Set<Range> intersectionOneWrapping(Range wrapping, Range other)
{
Set<Range> intersection = new HashSet<Range>(2);
if (other.contains(wrapping.right))
intersection.add(new Range(other.left, wrapping.right));
// need the extra compareto here because ranges are asymmetrical; wrapping.left _is not_ contained by the wrapping range
if (other.contains(wrapping.left) && wrapping.left.compareTo(other.right) < 0)
intersection.add(new Range(wrapping.left, other.right));
return Collections.unmodifiableSet(intersection);
}
public AbstractBounds createFrom(Token token)
{
if (token.equals(left))
return null;
return new Range(left, token);
}
public List<AbstractBounds> unwrap()
{
if (!isWrapAround() || right.equals(partitioner.getMinimumToken()))
return (List)Arrays.asList(this);
List<AbstractBounds> unwrapped = new ArrayList<AbstractBounds>(2);
unwrapped.add(new Range(left, partitioner.getMinimumToken()));
unwrapped.add(new Range(partitioner.getMinimumToken(), right));
return unwrapped;
}
/**
* Tells if the given range is a wrap around.
*/
public static boolean isWrapAround(Token left, Token right)
{
return compare(left,right) >= 0;
}
public static int compare(Token left, Token right)
{
ByteBuffer l,r;
if (left.token instanceof byte[])
{
l = ByteBuffer.wrap((byte[]) left.token);
}
else if (left.token instanceof ByteBuffer)
{
l = (ByteBuffer) left.token;
}
else
{
//Handles other token types
return left.compareTo(right);
}
if (right.token instanceof byte[])
{
r = ByteBuffer.wrap((byte[]) right.token);
}
else
{
r = (ByteBuffer) right.token;
}
return ByteBufferUtil.compareUnsigned(l, r);
}
public int compareTo(Range rhs)
{
/*
* If the range represented by the "this" pointer
* is a wrap around then it is the smaller one.
*/
if ( isWrapAround(left, right) )
return -1;
if ( isWrapAround(rhs.left, rhs.right) )
return 1;
return compare(right,rhs.right);
}
public static boolean isTokenInRanges(Token token, Iterable<Range> ranges)
{
assert ranges != null;
for (Range range : ranges)
{
if (range.contains(token))
{
return true;
}
}
return false;
}
@Override
public boolean equals(Object o)
{
if (!(o instanceof Range))
return false;
Range rhs = (Range)o;
return compare(left,rhs.left) == 0 && compare(right,rhs.right) == 0;
}
public String toString()
{
return "(" + left + "," + right + "]";
}
public boolean isWrapAround()
{
return isWrapAround(left, right);
}
}