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/*
* Copyright 2009 Google Inc.
*
* Licensed 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 java.util;
import static javaemul.internal.Coercions.ensureInt;
import static javaemul.internal.InternalPreconditions.checkArraySize;
import javaemul.internal.ArrayHelper;
/**
* This implementation uses a dense array holding bit groups of size 31 to keep track of when bits
* are set to true or false. Using 31 bits keeps our implementation within the range of V8's
* "tagged small integer" and improves performance. Using a dense array also makes access faster on
* V8.
*
* Not yet implemented:
* public static BitSet valueOf(ByteBuffer)
* public static BitSet valueOf(LongBuffer)
*/
public class BitSet {
private static final int WORD_MASK = 0x7fffffff;
private static final int BITS_PER_WORD = 31;
private final int[] array;
public BitSet() {
array = new int[0];
}
public BitSet(int nbits) {
checkArraySize(nbits);
int length = wordIndex(nbits - 1) + 1;
array = new int[0];
ArrayHelper.setLength(array, length);
}
private BitSet(int[] array) {
this.array = array;
}
private static void checkIndex(int bitIndex) {
if (bitIndex < 0) {
throw new IndexOutOfBoundsException("bitIndex < 0: " + bitIndex);
}
}
private static void checkRange(int fromIndex, int toIndex) {
if (fromIndex < 0 || toIndex < 0 || fromIndex > toIndex) {
throw new IndexOutOfBoundsException("fromIndex: " + fromIndex + ", toIndex: " + toIndex);
}
}
/**
* Converts from a bit index to a word index.
*
* @param bitIndex The bit index.
* @return The index of the word (array entry) holding that bit.
*/
private static int wordIndex(int bitIndex) {
return bitIndex / BITS_PER_WORD;
}
/**
* Converts from a word index to the lowest index of the bit stored in that word.
*
* @param wordIndex The word index.
* @return The lowest index of the bit stored in that word.
*/
private static int bitIndex(int wordIndex) {
return wordIndex * BITS_PER_WORD;
}
/**
* Computes the offset within a word for a bit index. Within a word, the offset counts from
* right to left and caps at 31. This helps leaving the highest bit as zero to ensure that
* each word is a tagged small integer in V8.
*
* @param bitIndex The bit index.
* @return The offset of the bit within a word, counting from right to left.
*/
private static int bitOffset(int bitIndex) {
return bitIndex % BITS_PER_WORD;
}
/**
* Sets all bits to true within the given range.
*
* @param fromIndex The lower bit index.
* @param toIndex The upper bit index.
*/
private static void setInternal(int[] array, int fromIndex, int toIndex) {
int first = wordIndex(fromIndex);
int last = wordIndex(toIndex);
maybeGrowArrayToIndex(array, last);
int startBit = bitOffset(fromIndex);
int endBit = bitOffset(toIndex);
if (first == last) {
// Set the bits in between first and last.
maskInWord(array, first, startBit, endBit);
} else {
// Set the bits from fromIndex to the next 31 bit boundary.
maskInWord(array, first, startBit, BITS_PER_WORD);
// Set the bits from the last 31 bit boundary to toIndex.
maskInWord(array, last, 0, endBit);
// Set everything in between.
for (int i = first + 1; i < last; i++) {
array[i] = WORD_MASK;
}
}
}
private static void maybeGrowArrayToIndex(int[] array, int newMaxIndex) {
// TODO: This code has a potential problem:
// If we grow the array more than 1024 places the array will degenerate into a map,
// we can work around this by adding 0 to the arrays.
int newLength = newMaxIndex + 1;
if (newLength > array.length) {
ArrayHelper.setLength(array, newLength);
}
}
/**
* Returns the index of the last word containing a true bit in an array, or -1 if none.
*
* @param array The array.
* @return The index of the last word containing a true bit, or -1 if none.
*/
private static int lastSetWordIndex(int[] array) {
int i = array.length - 1;
for (; i >= 0 && wordAt(array, i) == 0; --i) { }
return i;
}
/**
* Flips all bits in a word within the given range.
*
* @param array The array.
* @param index The word index.
* @param from The lower bit index.
* @param to The upper bit index.
*/
private static void flipMaskedWord(int[] array, int index, int from, int to) {
if (from == to) {
return;
}
to = 32 - to;
int word = wordAt(array, index);
word ^= ((0xffffffff >>> from) << (from + to)) >>> to;
array[index] = word & WORD_MASK;
}
/**
* Sets all bits to true in a word within the given bit range.
*
* @param array The array.
* @param index The word index.
* @param from The lower bit index.
* @param to The upper bit index.
*/
private static void maskInWord(int[] array, int index, int from, int to) {
if (from == to) {
return;
}
to = 32 - to;
int word = wordAt(array, index);
word |= ((0xffffffff >>> from) << (from + to)) >>> to;
array[index] = word & WORD_MASK;
}
/**
* Sets all bits to false in a word within the given bit range.
*
* @param array The array.
* @param index The word index.
* @param from The lower bit index.
* @param to The upper bit index.
*/
private static void maskOutWord(int[] array, int index, int from, int to) {
if (from == to) {
return;
}
int word = wordAt(array, index);
if (word == 0) {
return;
}
int mask;
if (from != 0) {
mask = 0xffffffff >>> (32 - from);
} else {
mask = 0;
}
// Shifting by 32 is the same as shifting by 0.
if (to != 32) {
mask |= 0xffffffff << to;
}
word &= mask;
array[index] = word & WORD_MASK;
}
private static int wordAt(int[] array, int index) {
return ensureInt(array[index]);
}
// GWT emulates integer with double and doesn't overflow. Enfore it by a integer mask.
private static int enforceOverflow(int value) {
return value & 0xffffffff;
}
public void and(BitSet set) {
// a & a is just a.
if (this == set) {
return;
}
// Truth table
//
// Case | a | b | a & b | Change?
// 1 | false | false | false | a is already false
// 2 | false | true | false | a is already false
// 3 | true | false | false | set a to false
// 4 | true | true | true | a is already true
//
// We only need to change something in case 3, so iterate over set a.
int limit = Math.min(array.length, set.array.length);
int index = 0;
for (; index < limit; index++) {
int word = wordAt(array, index);
if (word != 0) {
array[index] = word & wordAt(set.array, index);
}
}
Arrays.fill(array, index, array.length, 0);
}
public void andNot(BitSet set) {
// a & !a is false, and all falses result in an empty BitSet.
if (this == set) {
clear();
return;
}
// Truth table
//
// Case | a | b | !b | a & !b | Change?
// 1 | false | false | true | false | a is already false
// 2 | false | true | false | false | a is already false
// 3 | true | false | true | true | a is already true
// 4 | true | true | false | false | set a to false
//
// We only need to change something in case 4. Whenever b is true, a should be false, so
// iterate over set b.
int limit = Math.min(array.length, set.array.length);
for (int index = 0; index < limit; index++) {
int otherWord = wordAt(set.array, index);
if (otherWord != 0) {
int word = wordAt(array, index);
if (word != 0) {
array[index] = word & (~otherWord & WORD_MASK);
}
}
}
}
public int cardinality() {
int count = 0;
for (int i = 0; i < array.length; i++) {
count += Integer.bitCount(wordAt(array, i));
}
return count;
}
public void clear() {
ArrayHelper.setLength(array, 0);
}
public void clear(int bitIndex) {
checkIndex(bitIndex);
int index = wordIndex(bitIndex);
if (index >= array.length) {
return;
}
int word = wordAt(array, index);
if (word != 0) {
array[index] = word & ~(1 << bitOffset(bitIndex)) & WORD_MASK;
}
}
public void clear(int fromIndex, int toIndex) {
checkRange(fromIndex, toIndex);
if (fromIndex == toIndex) {
return;
}
int first = wordIndex(fromIndex);
if (first >= array.length) {
return;
}
int last = wordIndex(toIndex);
if (last >= array.length) {
toIndex = length();
last = wordIndex(toIndex);
}
int startBit = bitOffset(fromIndex);
int endBit = bitOffset(toIndex);
if (first == last) {
// Clear the bits in between first and last.
maskOutWord(array, first, startBit, endBit);
} else {
// Clear the bits from fromIndex to the next 31 bit boundary.
maskOutWord(array, first, startBit, BITS_PER_WORD);
// Clear the bits from the last 31 bit boundary to the toIndex.
maskOutWord(array, last, 0, endBit);
Arrays.fill(array, first + 1, last, 0);
}
}
public Object clone() {
return new BitSet(Arrays.copyOf(array, array.length));
}
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (!(obj instanceof BitSet)) {
return false;
}
BitSet other = (BitSet) obj;
int lastIndex = lastSetWordIndex(array);
if (lastIndex != lastSetWordIndex(other.array)) {
return false;
}
for (int index = 0; index <= lastIndex; index++) {
if (wordAt(array, index) != wordAt(other.array, index)) {
return false;
}
}
return true;
}
public void flip(int bitIndex) {
checkIndex(bitIndex);
int index = wordIndex(bitIndex);
int offset = bitOffset(bitIndex);
maybeGrowArrayToIndex(array, index);
int word = wordAt(array, index);
if (((word >>> offset) & 1) == 1) {
word = word & ~(1 << offset);
} else {
word = (word | (1 << offset));
}
array[index] = word & WORD_MASK;
}
public void flip(int fromIndex, int toIndex) {
checkRange(fromIndex, toIndex);
if (fromIndex == toIndex) {
return;
}
// If we are flipping bits beyond our length, we are setting them to true.
int length = length();
if (fromIndex >= length) {
setInternal(array, fromIndex, toIndex);
return;
}
if (toIndex >= length) {
setInternal(array, length, toIndex);
toIndex = length;
}
int first = wordIndex(fromIndex);
int last = wordIndex(toIndex);
int startBit = bitOffset(fromIndex);
int endBit = bitOffset(toIndex);
if (first == last) {
// Flip the bits in between first and last.
flipMaskedWord(array, first, startBit, endBit);
} else {
// Flip the bits from fromIndex to the next 31 bit boundary.
flipMaskedWord(array, first, startBit, BITS_PER_WORD);
// Flip the bits from the last 31 bit boundary to the toIndex.
flipMaskedWord(array, last, 0, endBit);
// Flip everything in between.
for (int i = first + 1; i < last; i++) {
array[i] = ~wordAt(array, i) & WORD_MASK;
}
}
}
public boolean get(int bitIndex) {
checkIndex(bitIndex);
int index = wordIndex(bitIndex);
// Shift and mask the bit out
return index < array.length && ((wordAt(array, index) >>> bitOffset(bitIndex)) & 1) == 1;
}
public BitSet get(int fromIndex, int toIndex) {
checkRange(fromIndex, toIndex);
int length = length();
if (length <= fromIndex || fromIndex == toIndex) {
return new BitSet(0);
}
toIndex = Math.min(toIndex, length);
// The bit shift offset for each group of bits
int rightShift = bitOffset(fromIndex);
if (rightShift == 0) {
int subFrom = wordIndex(fromIndex);
int subTo = wordIndex(toIndex + BITS_PER_WORD);
int[] subArray = Arrays.copyOfRange(array, subFrom, subTo);
int leftOvers = bitOffset(toIndex);
maskOutWord(subArray, subTo - subFrom - 1, leftOvers, BITS_PER_WORD);
return new BitSet(subArray);
}
int first = wordIndex(fromIndex);
int last = wordIndex(toIndex);
int[] subArray = new int[last - first + 1];
if (first == last) {
// Number of bits to cut from the end
int end = 32 - bitOffset(toIndex);
int word = wordAt(array, first);
subArray[0] = (word << end) >>> (rightShift + end);
} else {
// Fence post, carry over initial bits.
int word = wordAt(array, first);
// This holds the newly packed bits.
int current = word >>> rightShift;
// The raw index into the subset
int subIndex = 0;
// A left shift will be used to shift our bits to the top of "current".
int leftShift = BITS_PER_WORD - rightShift;
// Loop through everything in the middle.
for (int i = first + 1; i <= last; i++) {
word = wordAt(array, i);
// Shift out the bits from the top, OR them into current bits.
current |= word << leftShift;
subArray[subIndex++] = current & WORD_MASK;
// Carry over the unused bits.
current = word >>> rightShift;
}
// Fence post, flush out the extra bits, but don't go past the "end".
int end = 32 - bitOffset(toIndex);
current = (current << (rightShift + end)) >>> (rightShift + end);
subArray[subIndex] = current & WORD_MASK;
}
return new BitSet(subArray);
}
/**
* This hash is different than the one described in Sun's documentation. The
* described hash uses 64 bit integers and that's not practical in JavaScript.
*/
@Override
public int hashCode() {
// FNV constants
final int fnvOffset = 0x811c9dc5;
final int fnvPrime = 0x1000193;
final int lastIndex = lastSetWordIndex(array);
int hash = fnvOffset ^ lastIndex;
for (int i = 0; i <= lastIndex; i++) {
int value = wordAt(array, i);
// Hash one byte at a time using FNV1 and make sure we don't overflow 32 bit int.
hash = enforceOverflow(hash * fnvPrime) ^ (value & 0xff);
hash = enforceOverflow(hash * fnvPrime) ^ ((value >>> 8) & 0xff);
hash = enforceOverflow(hash * fnvPrime) ^ ((value >>> 16) & 0xff);
hash = enforceOverflow(hash * fnvPrime) ^ (value >>> 24);
}
return hash;
}
public boolean intersects(BitSet set) {
if (this == set) {
// If it has any set bits then it intersects itself.
return length() > 0;
}
int limit = Math.min(array.length, set.array.length);
for (int index = 0; index < limit; index++) {
int word = wordAt(array, index);
if (word != 0 && (word & wordAt(set.array, index)) != 0) {
return true;
}
}
return false;
}
public boolean isEmpty() {
return length() == 0;
}
public int length() {
int lastIndex = lastSetWordIndex(array);
if (lastIndex == -1) {
return 0;
}
// Compute the bit index of the leftmost bit.
int word = wordAt(array, lastIndex);
return bitIndex(lastIndex) + (32 - Integer.numberOfLeadingZeros(word));
}
public int nextClearBit(int fromIndex) {
checkIndex(fromIndex);
int index = wordIndex(fromIndex);
int length = array.length;
if (index >= length) {
return fromIndex;
}
// Special case for the first word.
int word = ~wordAt(array, index) & WORD_MASK;
word &= (WORD_MASK << bitOffset(fromIndex));
while (word == 0) {
if (++index >= length) {
return bitIndex(index);
}
word = ~wordAt(array, index) & WORD_MASK;
}
return bitIndex(index) + Integer.numberOfTrailingZeros(word);
}
public int nextSetBit(int fromIndex) {
checkIndex(fromIndex);
int index = wordIndex(fromIndex);
int length = array.length;
if (index >= length) {
return -1;
}
// Special case for the first word.
int word = wordAt(array, index) & (WORD_MASK << bitOffset(fromIndex));
while (word == 0) {
if (++index >= length) {
return -1;
}
word = wordAt(array, index);
}
return bitIndex(index) + Integer.numberOfTrailingZeros(word);
}
public int previousClearBit(int fromIndex) {
if (fromIndex == -1) {
return -1;
}
checkIndex(fromIndex);
int index = wordIndex(fromIndex);
if (index >= array.length) {
return fromIndex;
}
// Special case for the first word.
int word = ~wordAt(array, index) & WORD_MASK;
word &= (WORD_MASK >>> (BITS_PER_WORD - bitOffset(fromIndex) - 1));
while (word == 0) {
if (--index < 0) {
return -1;
}
word = ~wordAt(array, index) & WORD_MASK;
}
return bitIndex(index) + (32 - Integer.numberOfLeadingZeros(word)) - 1;
}
public int previousSetBit(int fromIndex) {
if (fromIndex == -1) {
return -1;
}
checkIndex(fromIndex);
int index = wordIndex(fromIndex);
if (index >= array.length) {
return length() - 1;
}
// Special case for the first word.
int word = wordAt(array, index) & (WORD_MASK >>> (BITS_PER_WORD - bitOffset(fromIndex) - 1));
while (word == 0) {
if (--index < 0) {
return -1;
}
word = wordAt(array, index);
}
return bitIndex(index) + (32 - Integer.numberOfLeadingZeros(word)) - 1;
}
public void or(BitSet set) {
// a | a is just a.
if (this == set) {
return;
}
maybeGrowArrayToIndex(array, set.array.length - 1);
// Truth table
//
// Case | a | b | a | b | Change?
// 1 | false | false | false | a is already false
// 2 | false | true | true | set a to true
// 3 | true | false | true | a is already true
// 4 | true | true | true | a is already true
//
// We only need to change something in case 2. Case 2 only happens when b is true, so iterate
// over set b
for (int index = 0; index < set.array.length; index++) {
int word = wordAt(set.array, index);
if (word != 0) {
array[index] = wordAt(array, index) | word;
}
}
}
public void set(int bitIndex) {
checkIndex(bitIndex);
int index = wordIndex(bitIndex);
maybeGrowArrayToIndex(array, index);
array[index] = wordAt(array, index) | (1 << bitOffset(bitIndex));
}
public void set(int bitIndex, boolean value) {
if (value) {
set(bitIndex);
} else {
clear(bitIndex);
}
}
public void set(int fromIndex, int toIndex) {
checkRange(fromIndex, toIndex);
if (fromIndex != toIndex) {
setInternal(array, fromIndex, toIndex);
}
}
public void set(int fromIndex, int toIndex, boolean value) {
if (value) {
set(fromIndex, toIndex);
} else {
clear(fromIndex, toIndex);
}
}
public int size() {
return array.length * 32;
}
@Override
public String toString() {
if (isEmpty()) {
return "{}";
}
StringBuilder sb = new StringBuilder("{");
int next = nextSetBit(0);
sb.append(next);
while ((next = nextSetBit(next + 1)) != -1) {
sb.append(", ");
sb.append(next);
}
sb.append("}");
return sb.toString();
}
public void xor(BitSet set) {
// a ^ a is all false, so return an empty BitSet.
if (this == set) {
clear();
return;
}
maybeGrowArrayToIndex(array, set.array.length - 1);
// Truth table
//
// Case | a | b | a ^ b | Change?
// 1 | false | false | false | a is already false
// 2 | false | true | true | set a to true
// 3 | true | false | true | a is already true
// 4 | true | true | false | set a to false
//
// We need to change something in cases 2 and 4. Cases 2 and 4 only happen when b is true,
// so iterate over set b.
for (int index = 0; index < set.array.length; index++) {
int word = wordAt(set.array, index);
if (word != 0) {
array[index] = wordAt(array, index) ^ word;
}
}
}
public byte[] toByteArray() {
int nbits = length();
int nbytes = nbits / Byte.SIZE;
if (nbits % Byte.SIZE != 0) {
nbytes++;
}
byte[] bytes = new byte[nbytes];
int bitOffset = 0;
for (int i = 0; i < nbytes; i++) {
bytes[i] = getByte(array, bitOffset);
bitOffset += Byte.SIZE;
}
return bytes;
}
public long[] toLongArray() {
int nbits = length();
int nlongs = nbits / Long.SIZE;
if (nbits % Long.SIZE != 0) {
nlongs++;
}
long[] longs = new long[nlongs];
int bitOffset = 0;
for (int i = 0; i < nlongs; i++) {
longs[i] = getLong(array, bitOffset);
bitOffset += Long.SIZE;
}
return longs;
}
private static byte getByte(int[] words, int bitIndex) {
int wordIndex = wordIndex(bitIndex);
if (wordIndex >= words.length) {
return 0;
}
int bitOffset = bitOffset(bitIndex);
int word = wordAt(words, wordIndex);
int b = (word >>> bitOffset);
int leftBits = Byte.SIZE - BITS_PER_WORD + bitOffset;
if (leftBits > 0 && wordIndex + 1 < words.length) {
word = wordAt(words, wordIndex + 1);
if (word != 0) {
word &= ~(WORD_MASK << leftBits);
word <<= (Byte.SIZE - leftBits);
b |= word;
}
}
return (byte) (b & 0xff);
}
private static int getInt(int[] words, int bitIndex) {
byte b1 = getByte(words, bitIndex);
byte b2 = getByte(words, bitIndex + 8);
byte b3 = getByte(words, bitIndex + 16);
byte b4 = getByte(words, bitIndex + 24);
return (b1 & 0xff) | ((b2 & 0xff) << 8) | ((b3 & 0xff) << 16) | ((b4 & 0xff) << 24);
}
private static long getLong(int[] words, int bitIndex) {
int low = getInt(words, bitIndex);
int high = getInt(words, bitIndex + 32);
return ((long) high << 32) | (low & 0xffff_ffffL);
}
public static BitSet valueOf(byte[] words) {
int len = words.length;
while (len > 0 && words[len - 1] == 0) {
len--;
}
int[] array = new int[len * Byte.SIZE];
int bitIndex = 0;
for (int i = 0; i < len; i++) {
addByte(array, words[i], bitIndex);
bitIndex += Byte.SIZE;
}
return new BitSet(array);
}
public static BitSet valueOf(long[] words) {
int len = words.length;
while (len > 0 && words[len - 1] == 0) {
len--;
}
int[] array = new int[len * Long.SIZE];
int bitIndex = 0;
for (int i = 0; i < len; i++) {
addLong(array, words[i], bitIndex);
bitIndex += Long.SIZE;
}
return new BitSet(array);
}
private static void addByte(int[] words, byte bits, int bitIndex) {
if (bits != 0) {
int wordIndex = wordIndex(bitIndex);
int bitOffset = bitOffset(bitIndex);
int first = ((bits & 0xff) << bitOffset) & WORD_MASK;
if (first != 0) {
words[wordIndex] = wordAt(words, wordIndex) | first;
}
int second = bitOffset == 0 ? 0 : (bits & 0xff) >>> (BITS_PER_WORD - bitOffset);
if (second != 0) {
words[wordIndex + 1] = wordAt(words, wordIndex + 1) | second;
}
}
}
private static void addInt(int[] words, int bits, int bitIndex) {
if (bits != 0) {
addByte(words, (byte) (bits & 0xff), bitIndex);
addByte(words, (byte) ((bits >> 8) & 0xff), bitIndex + Byte.SIZE);
addByte(words, (byte) ((bits >> 16) & 0xff), bitIndex + 2 * Byte.SIZE);
addByte(words, (byte) ((bits >> 24) & 0xff), bitIndex + 3 * Byte.SIZE);
}
}
private static void addLong(int[] words, long bits, int bitIndex) {
if (bits != 0) {
int low = (int) bits;
addInt(words, low, bitIndex);
int high = (int) (bits >>> 32);
addInt(words, high, bitIndex + Integer.SIZE);
}
}
}
