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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
/**
* A simple, fixed-size bit set implementation. This implementation is fast because it avoids
* safety/bound checking.
*/
class BitSet(numBits: Int) extends Serializable {
private val words = new Array[Long](bit2words(numBits))
private val numWords = words.length
/**
* Compute the capacity (number of bits) that can be represented
* by this bitset.
*/
def capacity: Int = numWords * 64
/**
* Clear all set bits.
*/
def clear(): Unit = {
var i = 0
while (i < numWords) {
words(i) = 0L
i += 1
}
}
/**
* Set all the bits up to a given index
*/
def setUntil(bitIndex: Int) {
val wordIndex = bitIndex >> 6 // divide by 64
var i = 0
while(i < wordIndex) { words(i) = -1; i += 1 }
if(wordIndex < words.length) {
// Set the remaining bits (note that the mask could still be zero)
val mask = ~(-1L << (bitIndex & 0x3f))
words(wordIndex) |= mask
}
}
/**
* Compute the bit-wise AND of the two sets returning the
* result.
*/
def &(other: BitSet): BitSet = {
val newBS = new BitSet(math.max(capacity, other.capacity))
val smaller = math.min(numWords, other.numWords)
assert(newBS.numWords >= numWords)
assert(newBS.numWords >= other.numWords)
var ind = 0
while( ind < smaller ) {
newBS.words(ind) = words(ind) & other.words(ind)
ind += 1
}
newBS
}
/**
* Compute the bit-wise OR of the two sets returning the
* result.
*/
def |(other: BitSet): BitSet = {
val newBS = new BitSet(math.max(capacity, other.capacity))
assert(newBS.numWords >= numWords)
assert(newBS.numWords >= other.numWords)
val smaller = math.min(numWords, other.numWords)
var ind = 0
while( ind < smaller ) {
newBS.words(ind) = words(ind) | other.words(ind)
ind += 1
}
while( ind < numWords ) {
newBS.words(ind) = words(ind)
ind += 1
}
while( ind < other.numWords ) {
newBS.words(ind) = other.words(ind)
ind += 1
}
newBS
}
/**
* Compute the symmetric difference by performing bit-wise XOR of the two sets returning the
* result.
*/
def ^(other: BitSet): BitSet = {
val newBS = new BitSet(math.max(capacity, other.capacity))
val smaller = math.min(numWords, other.numWords)
var ind = 0
while (ind < smaller) {
newBS.words(ind) = words(ind) ^ other.words(ind)
ind += 1
}
if (ind < numWords) {
Array.copy( words, ind, newBS.words, ind, numWords - ind )
}
if (ind < other.numWords) {
Array.copy( other.words, ind, newBS.words, ind, other.numWords - ind )
}
newBS
}
/**
* Compute the difference of the two sets by performing bit-wise AND-NOT returning the
* result.
*/
def andNot(other: BitSet): BitSet = {
val newBS = new BitSet(capacity)
val smaller = math.min(numWords, other.numWords)
var ind = 0
while (ind < smaller) {
newBS.words(ind) = words(ind) & ~other.words(ind)
ind += 1
}
if (ind < numWords) {
Array.copy( words, ind, newBS.words, ind, numWords - ind )
}
newBS
}
/**
* Sets the bit at the specified index to true.
* @param index the bit index
*/
def set(index: Int) {
val bitmask = 1L << (index & 0x3f) // mod 64 and shift
words(index >> 6) |= bitmask // div by 64 and mask
}
def unset(index: Int) {
val bitmask = 1L << (index & 0x3f) // mod 64 and shift
words(index >> 6) &= ~bitmask // div by 64 and mask
}
/**
* Return the value of the bit with the specified index. The value is true if the bit with
* the index is currently set in this BitSet; otherwise, the result is false.
*
* @param index the bit index
* @return the value of the bit with the specified index
*/
def get(index: Int): Boolean = {
val bitmask = 1L << (index & 0x3f) // mod 64 and shift
(words(index >> 6) & bitmask) != 0 // div by 64 and mask
}
/**
* Get an iterator over the set bits.
*/
def iterator: Iterator[Int] = new Iterator[Int] {
var ind = nextSetBit(0)
override def hasNext: Boolean = ind >= 0
override def next(): Int = {
val tmp = ind
ind = nextSetBit(ind + 1)
tmp
}
}
/** Return the number of bits set to true in this BitSet. */
def cardinality(): Int = {
var sum = 0
var i = 0
while (i < numWords) {
sum += java.lang.Long.bitCount(words(i))
i += 1
}
sum
}
/**
* Returns the index of the first bit that is set to true that occurs on or after the
* specified starting index. If no such bit exists then -1 is returned.
*
* To iterate over the true bits in a BitSet, use the following loop:
*
* for (int i = bs.nextSetBit(0); i >= 0; i = bs.nextSetBit(i+1)) {
* // operate on index i here
* }
*
* @param fromIndex the index to start checking from (inclusive)
* @return the index of the next set bit, or -1 if there is no such bit
*/
def nextSetBit(fromIndex: Int): Int = {
var wordIndex = fromIndex >> 6
if (wordIndex >= numWords) {
return -1
}
// Try to find the next set bit in the current word
val subIndex = fromIndex & 0x3f
var word = words(wordIndex) >> subIndex
if (word != 0) {
return (wordIndex << 6) + subIndex + java.lang.Long.numberOfTrailingZeros(word)
}
// Find the next set bit in the rest of the words
wordIndex += 1
while (wordIndex < numWords) {
word = words(wordIndex)
if (word != 0) {
return (wordIndex << 6) + java.lang.Long.numberOfTrailingZeros(word)
}
wordIndex += 1
}
-1
}
/** Return the number of longs it would take to hold numBits. */
private def bit2words(numBits: Int) = ((numBits - 1) >> 6) + 1
}
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