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fastutil extends the Java Collections Framework by providing type-specific maps, sets, lists and priority queues with a small memory footprint and fast access and insertion; provides also big (64-bit) arrays, sets and lists, and fast, practical I/O classes for binary and text files.

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 * Copyright (C) 2002-2016 Sebastiano Vigna
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package it.unimi.dsi.fastutil.bytes;

import it.unimi.dsi.fastutil.Hash;
import it.unimi.dsi.fastutil.HashCommon;
import static it.unimi.dsi.fastutil.HashCommon.arraySize;
import static it.unimi.dsi.fastutil.HashCommon.maxFill;
import java.util.Arrays;
import java.util.Collection;
import java.util.Iterator;
import java.util.NoSuchElementException;

/**
 * A type-specific hash set with a fast, small-footprint implementation whose
 * {@linkplain it.unimi.dsi.fastutil.Hash.Strategy hashing strategy} is
 * specified at creation time.
 *
 * 

* Instances of this class use a hash table to represent a set. The table is * filled up to a specified load factor, and then doubled in size to * accommodate new entries. If the table is emptied below one fourth of * the load factor, it is halved in size. However, halving is not performed when * deleting entries from an iterator, as it would interfere with the iteration * process. * *

* Note that {@link #clear()} does not modify the hash table size. Rather, a * family of {@linkplain #trim() trimming methods} lets you control the size of * the table; this is particularly useful if you reuse instances of this class. * * @see Hash * @see HashCommon */ public class ByteOpenCustomHashSet extends AbstractByteSet implements java.io.Serializable, Cloneable, Hash { private static final long serialVersionUID = 0L; private static final boolean ASSERTS = false; /** The array of keys. */ protected transient byte[] key; /** The mask for wrapping a position counter. */ protected transient int mask; /** Whether this set contains the null key. */ protected transient boolean containsNull; /** The hash strategy of this custom set. */ protected it.unimi.dsi.fastutil.bytes.ByteHash.Strategy strategy; /** * The current table size. Note that an additional element is allocated for * storing the null key. */ protected transient int n; /** * Threshold after which we rehash. It must be the table size times * {@link #f}. */ protected transient int maxFill; /** Number of entries in the set (including the null key, if present). */ protected int size; /** The acceptable load factor. */ protected final float f; /** * Creates a new hash set. * *

* The actual table size will be the least power of two greater than * expected/f. * * @param expected * the expected number of elements in the hash set. * @param f * the load factor. * @param strategy * the strategy. */ public ByteOpenCustomHashSet(final int expected, final float f, final it.unimi.dsi.fastutil.bytes.ByteHash.Strategy strategy) { this.strategy = strategy; if (f <= 0 || f > 1) throw new IllegalArgumentException("Load factor must be greater than 0 and smaller than or equal to 1"); if (expected < 0) throw new IllegalArgumentException("The expected number of elements must be nonnegative"); this.f = f; n = arraySize(expected, f); mask = n - 1; maxFill = maxFill(n, f); key = new byte[n + 1]; } /** * Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load * factor. * * @param expected * the expected number of elements in the hash set. * @param strategy * the strategy. */ public ByteOpenCustomHashSet(final int expected, final it.unimi.dsi.fastutil.bytes.ByteHash.Strategy strategy) { this(expected, DEFAULT_LOAD_FACTOR, strategy); } /** * Creates a new hash set with initial expected * {@link Hash#DEFAULT_INITIAL_SIZE} elements and * {@link Hash#DEFAULT_LOAD_FACTOR} as load factor. * * @param strategy * the strategy. */ public ByteOpenCustomHashSet(final it.unimi.dsi.fastutil.bytes.ByteHash.Strategy strategy) { this(DEFAULT_INITIAL_SIZE, DEFAULT_LOAD_FACTOR, strategy); } /** * Creates a new hash set copying a given collection. * * @param c * a {@link Collection} to be copied into the new hash set. * @param f * the load factor. * @param strategy * the strategy. */ public ByteOpenCustomHashSet(final Collection c, final float f, final it.unimi.dsi.fastutil.bytes.ByteHash.Strategy strategy) { this(c.size(), f, strategy); addAll(c); } /** * Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load * factor copying a given collection. * * @param c * a {@link Collection} to be copied into the new hash set. * @param strategy * the strategy. */ public ByteOpenCustomHashSet(final Collection c, final it.unimi.dsi.fastutil.bytes.ByteHash.Strategy strategy) { this(c, DEFAULT_LOAD_FACTOR, strategy); } /** * Creates a new hash set copying a given type-specific collection. * * @param c * a type-specific collection to be copied into the new hash set. * @param f * the load factor. * @param strategy * the strategy. */ public ByteOpenCustomHashSet(final ByteCollection c, final float f, it.unimi.dsi.fastutil.bytes.ByteHash.Strategy strategy) { this(c.size(), f, strategy); addAll(c); } /** * Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load * factor copying a given type-specific collection. * * @param c * a type-specific collection to be copied into the new hash set. * @param strategy * the strategy. */ public ByteOpenCustomHashSet(final ByteCollection c, final it.unimi.dsi.fastutil.bytes.ByteHash.Strategy strategy) { this(c, DEFAULT_LOAD_FACTOR, strategy); } /** * Creates a new hash set using elements provided by a type-specific * iterator. * * @param i * a type-specific iterator whose elements will fill the set. * @param f * the load factor. * @param strategy * the strategy. */ public ByteOpenCustomHashSet(final ByteIterator i, final float f, final it.unimi.dsi.fastutil.bytes.ByteHash.Strategy strategy) { this(DEFAULT_INITIAL_SIZE, f, strategy); while (i.hasNext()) add(i.nextByte()); } /** * Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load * factor using elements provided by a type-specific iterator. * * @param i * a type-specific iterator whose elements will fill the set. * @param strategy * the strategy. */ public ByteOpenCustomHashSet(final ByteIterator i, final it.unimi.dsi.fastutil.bytes.ByteHash.Strategy strategy) { this(i, DEFAULT_LOAD_FACTOR, strategy); } /** * Creates a new hash set using elements provided by an iterator. * * @param i * an iterator whose elements will fill the set. * @param f * the load factor. * @param strategy * the strategy. */ public ByteOpenCustomHashSet(final Iterator i, final float f, final it.unimi.dsi.fastutil.bytes.ByteHash.Strategy strategy) { this(ByteIterators.asByteIterator(i), f, strategy); } /** * Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load * factor using elements provided by an iterator. * * @param i * an iterator whose elements will fill the set. * @param strategy * the strategy. */ public ByteOpenCustomHashSet(final Iterator i, final it.unimi.dsi.fastutil.bytes.ByteHash.Strategy strategy) { this(ByteIterators.asByteIterator(i), strategy); } /** * Creates a new hash set and fills it with the elements of a given array. * * @param a * an array whose elements will be used to fill the set. * @param offset * the first element to use. * @param length * the number of elements to use. * @param f * the load factor. * @param strategy * the strategy. */ public ByteOpenCustomHashSet(final byte[] a, final int offset, final int length, final float f, final it.unimi.dsi.fastutil.bytes.ByteHash.Strategy strategy) { this(length < 0 ? 0 : length, f, strategy); ByteArrays.ensureOffsetLength(a, offset, length); for (int i = 0; i < length; i++) add(a[offset + i]); } /** * Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load * factor and fills it with the elements of a given array. * * @param a * an array whose elements will be used to fill the set. * @param offset * the first element to use. * @param length * the number of elements to use. * @param strategy * the strategy. */ public ByteOpenCustomHashSet(final byte[] a, final int offset, final int length, final it.unimi.dsi.fastutil.bytes.ByteHash.Strategy strategy) { this(a, offset, length, DEFAULT_LOAD_FACTOR, strategy); } /** * Creates a new hash set copying the elements of an array. * * @param a * an array to be copied into the new hash set. * @param f * the load factor. * @param strategy * the strategy. */ public ByteOpenCustomHashSet(final byte[] a, final float f, final it.unimi.dsi.fastutil.bytes.ByteHash.Strategy strategy) { this(a, 0, a.length, f, strategy); } /** * Creates a new hash set with {@link Hash#DEFAULT_LOAD_FACTOR} as load * factor copying the elements of an array. * * @param a * an array to be copied into the new hash set. * @param strategy * the strategy. */ public ByteOpenCustomHashSet(final byte[] a, final it.unimi.dsi.fastutil.bytes.ByteHash.Strategy strategy) { this(a, DEFAULT_LOAD_FACTOR, strategy); } /** * Returns the hashing strategy. * * @return the hashing strategy of this custom hash set. */ public it.unimi.dsi.fastutil.bytes.ByteHash.Strategy strategy() { return strategy; } private int realSize() { return containsNull ? size - 1 : size; } private void ensureCapacity(final int capacity) { final int needed = arraySize(capacity, f); if (needed > n) rehash(needed); } private void tryCapacity(final long capacity) { final int needed = (int) Math.min(1 << 30, Math.max(2, HashCommon.nextPowerOfTwo((long) Math.ceil(capacity / f)))); if (needed > n) rehash(needed); } /** {@inheritDoc} */ public boolean addAll(ByteCollection c) { if (f <= .5) ensureCapacity(c.size()); // The resulting collection will // be sized for c.size() // elements else tryCapacity(size() + c.size()); // The resulting collection will be // tentatively sized for size() // + c.size() elements return super.addAll(c); } /** {@inheritDoc} */ public boolean addAll(Collection c) { // The resulting collection will be at least c.size() big if (f <= .5) ensureCapacity(c.size()); // The resulting collection will // be sized for c.size() // elements else tryCapacity(size() + c.size()); // The resulting collection will be // tentatively sized for size() // + c.size() elements return super.addAll(c); } public boolean add(final byte k) { int pos; if ((strategy.equals((k), ((byte) 0)))) { if (containsNull) return false; containsNull = true; key[n] = k; } else { byte curr; final byte[] key = this.key; // The starting point. if (!((curr = key[pos = (it.unimi.dsi.fastutil.HashCommon.mix(strategy.hashCode(k))) & mask]) == ((byte) 0))) { if ((strategy.equals((curr), (k)))) return false; while (!((curr = key[pos = (pos + 1) & mask]) == ((byte) 0))) if ((strategy.equals((curr), (k)))) return false; } key[pos] = k; } if (size++ >= maxFill) rehash(arraySize(size + 1, f)); if (ASSERTS) checkTable(); return true; } /** * Shifts left entries with the specified hash code, starting at the * specified position, and empties the resulting free entry. * * @param pos * a starting position. */ protected final void shiftKeys(int pos) { // Shift entries with the same hash. int last, slot; byte curr; final byte[] key = this.key; for (;;) { pos = ((last = pos) + 1) & mask; for (;;) { if (((curr = key[pos]) == ((byte) 0))) { key[last] = ((byte) 0); return; } slot = (it.unimi.dsi.fastutil.HashCommon.mix(strategy.hashCode(curr))) & mask; if (last <= pos ? last >= slot || slot > pos : last >= slot && slot > pos) break; pos = (pos + 1) & mask; } key[last] = curr; } } private boolean removeEntry(final int pos) { size--; shiftKeys(pos); if (size < maxFill / 4 && n > DEFAULT_INITIAL_SIZE) rehash(n / 2); return true; } private boolean removeNullEntry() { containsNull = false; key[n] = ((byte) 0); size--; if (size < maxFill / 4 && n > DEFAULT_INITIAL_SIZE) rehash(n / 2); return true; } public boolean rem(final byte k) { if ((strategy.equals((k), ((byte) 0)))) { if (containsNull) return removeNullEntry(); return false; } byte curr; final byte[] key = this.key; int pos; // The starting point. if (((curr = key[pos = (it.unimi.dsi.fastutil.HashCommon.mix(strategy.hashCode(k))) & mask]) == ((byte) 0))) return false; if ((strategy.equals((k), (curr)))) return removeEntry(pos); while (true) { if (((curr = key[pos = (pos + 1) & mask]) == ((byte) 0))) return false; if ((strategy.equals((k), (curr)))) return removeEntry(pos); } } public boolean contains(final byte k) { if ((strategy.equals((k), ((byte) 0)))) return containsNull; byte curr; final byte[] key = this.key; int pos; // The starting point. if (((curr = key[pos = (it.unimi.dsi.fastutil.HashCommon.mix(strategy.hashCode(k))) & mask]) == ((byte) 0))) return false; if ((strategy.equals((k), (curr)))) return true; while (true) { if (((curr = key[pos = (pos + 1) & mask]) == ((byte) 0))) return false; if ((strategy.equals((k), (curr)))) return true; } } /* * Removes all elements from this set. * *

To increase object reuse, this method does not change the table size. * If you want to reduce the table size, you must use {@link #trim()}. * */ public void clear() { if (size == 0) return; size = 0; containsNull = false; Arrays.fill(key, ((byte) 0)); } public int size() { return size; } public boolean isEmpty() { return size == 0; } /** * A no-op for backward compatibility. * * @param growthFactor * unused. * @deprecated Since fastutil 6.1.0, hash tables are doubled * when they are too full. */ @Deprecated public void growthFactor(int growthFactor) { } /** * Gets the growth factor (2). * * @return the growth factor of this set, which is fixed (2). * @see #growthFactor(int) * @deprecated Since fastutil 6.1.0, hash tables are doubled * when they are too full. */ @Deprecated public int growthFactor() { return 16; } /** An iterator over a hash set. */ private class SetIterator extends AbstractByteIterator { /** * The index of the last entry returned, if positive or zero; initially, * {@link #n}. If negative, the last element returned was that of index * {@code - pos - 1} from the {@link #wrapped} list. */ int pos = n; /** * The index of the last entry that has been returned (more precisely, * the value of {@link #pos} if {@link #pos} is positive, or * {@link Integer#MIN_VALUE} if {@link #pos} is negative). It is -1 if * either we did not return an entry yet, or the last returned entry has * been removed. */ int last = -1; /** * A downward counter measuring how many entries must still be returned. */ int c = size; /** A boolean telling us whether we should return the null key. */ boolean mustReturnNull = ByteOpenCustomHashSet.this.containsNull; /** * A lazily allocated list containing elements that have wrapped around * the table because of removals. */ ByteArrayList wrapped; public boolean hasNext() { return c != 0; } public byte nextByte() { if (!hasNext()) throw new NoSuchElementException(); c--; if (mustReturnNull) { mustReturnNull = false; last = n; return key[n]; } final byte key[] = ByteOpenCustomHashSet.this.key; for (;;) { if (--pos < 0) { // We are just enumerating elements from the wrapped list. last = Integer.MIN_VALUE; return wrapped.getByte(-pos - 1); } if (!((key[pos]) == ((byte) 0))) return key[last = pos]; } } /** * Shifts left entries with the specified hash code, starting at the * specified position, and empties the resulting free entry. * * @param pos * a starting position. */ private final void shiftKeys(int pos) { // Shift entries with the same hash. int last, slot; byte curr; final byte[] key = ByteOpenCustomHashSet.this.key; for (;;) { pos = ((last = pos) + 1) & mask; for (;;) { if (((curr = key[pos]) == ((byte) 0))) { key[last] = ((byte) 0); return; } slot = (it.unimi.dsi.fastutil.HashCommon.mix(strategy.hashCode(curr))) & mask; if (last <= pos ? last >= slot || slot > pos : last >= slot && slot > pos) break; pos = (pos + 1) & mask; } if (pos < last) { // Wrapped entry. if (wrapped == null) wrapped = new ByteArrayList(2); wrapped.add(key[pos]); } key[last] = curr; } } public void remove() { if (last == -1) throw new IllegalStateException(); if (last == n) { ByteOpenCustomHashSet.this.containsNull = false; ByteOpenCustomHashSet.this.key[n] = ((byte) 0); } else if (pos >= 0) shiftKeys(last); else { // We're removing wrapped entries. ByteOpenCustomHashSet.this.rem(wrapped.getByte(-pos - 1)); last = -1; // Note that we must not decrement size return; } size--; last = -1; // You can no longer remove this entry. if (ASSERTS) checkTable(); } } public ByteIterator iterator() { return new SetIterator(); } /** * A no-op for backward compatibility. The kind of tables implemented by * this class never need rehashing. * *

* If you need to reduce the table size to fit exactly this set, use * {@link #trim()}. * * @return true. * @see #trim() * @deprecated A no-op. */ @Deprecated public boolean rehash() { return true; } /** * Rehashes this set, making the table as small as possible. * *

* This method rehashes the table to the smallest size satisfying the load * factor. It can be used when the set will not be changed anymore, so to * optimize access speed and size. * *

* If the table size is already the minimum possible, this method does * nothing. * * @return true if there was enough memory to trim the set. * @see #trim(int) */ public boolean trim() { final int l = arraySize(size, f); if (l >= n || size > maxFill(l, f)) return true; try { rehash(l); } catch (OutOfMemoryError cantDoIt) { return false; } return true; } /** * Rehashes this set if the table is too large. * *

* Let N be the smallest table size that can hold * max(n,{@link #size()}) entries, still satisfying the load * factor. If the current table size is smaller than or equal to * N, this method does nothing. Otherwise, it rehashes this set * in a table of size N. * *

* This method is useful when reusing sets. {@linkplain #clear() Clearing a * set} leaves the table size untouched. If you are reusing a set many * times, you can call this method with a typical size to avoid keeping * around a very large table just because of a few large transient sets. * * @param n * the threshold for the trimming. * @return true if there was enough memory to trim the set. * @see #trim() */ public boolean trim(final int n) { final int l = HashCommon.nextPowerOfTwo((int) Math.ceil(n / f)); if (l >= n || size > maxFill(l, f)) return true; try { rehash(l); } catch (OutOfMemoryError cantDoIt) { return false; } return true; } /** * Rehashes the set. * *

* This method implements the basic rehashing strategy, and may be overriden * by subclasses implementing different rehashing strategies (e.g., * disk-based rehashing). However, you should not override this method * unless you understand the internal workings of this class. * * @param newN * the new size */ protected void rehash(final int newN) { final byte key[] = this.key; final int mask = newN - 1; // Note that this is used by the hashing // macro final byte newKey[] = new byte[newN + 1]; int i = n, pos; for (int j = realSize(); j-- != 0;) { while (((key[--i]) == ((byte) 0))) ; if (!((newKey[pos = (it.unimi.dsi.fastutil.HashCommon.mix(strategy.hashCode(key[i]))) & mask]) == ((byte) 0))) while (!((newKey[pos = (pos + 1) & mask]) == ((byte) 0))) ; newKey[pos] = key[i]; } n = newN; this.mask = mask; maxFill = maxFill(n, f); this.key = newKey; } /** * Returns a deep copy of this set. * *

* This method performs a deep copy of this hash set; the data stored in the * set, however, is not cloned. Note that this makes a difference only for * object keys. * * @return a deep copy of this set. */ public ByteOpenCustomHashSet clone() { ByteOpenCustomHashSet c; try { c = (ByteOpenCustomHashSet) super.clone(); } catch (CloneNotSupportedException cantHappen) { throw new InternalError(); } c.key = key.clone(); c.containsNull = containsNull; c.strategy = strategy; return c; } /** * Returns a hash code for this set. * * This method overrides the generic method provided by the superclass. * Since equals() is not overriden, it is important that the * value returned by this method is the same value as the one returned by * the overriden method. * * @return a hash code for this set. */ public int hashCode() { int h = 0; for (int j = realSize(), i = 0; j-- != 0;) { while (((key[i]) == ((byte) 0))) i++; h += (strategy.hashCode(key[i])); i++; } // Zero / null have hash zero. return h; } private void writeObject(java.io.ObjectOutputStream s) throws java.io.IOException { final ByteIterator i = iterator(); s.defaultWriteObject(); for (int j = size; j-- != 0;) s.writeByte(i.nextByte()); } private void readObject(java.io.ObjectInputStream s) throws java.io.IOException, ClassNotFoundException { s.defaultReadObject(); n = arraySize(size, f); maxFill = maxFill(n, f); mask = n - 1; final byte key[] = this.key = new byte[n + 1]; byte k; for (int i = size, pos; i-- != 0;) { k = s.readByte(); if ((strategy.equals((k), ((byte) 0)))) { pos = n; containsNull = true; } else { if (!((key[pos = (it.unimi.dsi.fastutil.HashCommon.mix(strategy.hashCode(k))) & mask]) == ((byte) 0))) while (!((key[pos = (pos + 1) & mask]) == ((byte) 0))) ; } key[pos] = k; } if (ASSERTS) checkTable(); } private void checkTable() { } }





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