Package org.apache.lucene.internal.hppc

Class CharHashSet

java.lang.Object
org.apache.lucene.internal.hppc.CharHashSet
All Implemented Interfaces:
Cloneable, Iterable<CharCursor>, Accountable
public class CharHashSet extends Object implements Iterable<CharCursor>, Accountable, Cloneable
A hash set of chars, implemented using open addressing with linear probing for collision resolution.

Mostly forked and trimmed from com.carrotsearch.hppc.CharHashSet

github: https://github.com/carrotsearch/hppc release 0.10.0

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

  • Nested Class Summary

    Nested Classes
    Modifier and Type
    Class
    Description
    protected final class 
    CharHashSet.EntryIterator
    An iterator implementation for iterator().

  • Field Summary

    Fields
    Modifier and Type
    Field
    Description
    protected int
    assigned
    The number of stored keys (assigned key slots), excluding the special "empty" key, if any.
    protected boolean
    hasEmptyKey
    Special treatment for the "empty slot" key marker.
    protected int
    iterationSeed
    Seed used to ensure the hash iteration order is different from an iteration to another.
    char[]
    keys
    The hash array holding keys.
    protected double
    loadFactor
    The load factor for keys.
    protected int
    mask
    Mask for slot scans in keys.
    protected int
    resizeAt
    Expand (rehash) keys when assigned hits this value.

    Fields inherited from interface org.apache.lucene.util.Accountable

    NULL_ACCOUNTABLE

  • Constructor Summary

    Constructors
    Constructor
    Description
    CharHashSet()
    New instance with sane defaults.
    CharHashSet(int expectedElements)
    New instance with sane defaults.
    CharHashSet(int expectedElements, double loadFactor)
    New instance with the provided defaults.
    CharHashSet(CharHashSet set)
    New instance copying elements from another set.

  • Method Summary

    Modifier and Type
    Method
    Description
    boolean
    add(char key)
     
    final int
    addAll(char... elements)
    Adds all elements from the given list (vararg) to this set.
    int
    addAll(Iterable<? extends CharCursor> iterable)
    Adds all elements from the given iterable to this set.
    int
    addAll(CharHashSet set)
    Adds all elements from the given set to this set.
    protected void
    allocateBuffers(int arraySize)
    Allocate new internal buffers.
    protected void
    allocateThenInsertThenRehash(int slot, char pendingKey)
    This method is invoked when there is a new key to be inserted into the buffer but there is not enough empty slots to do so.
    void
    clear()
     
    CharHashSet
    clone()
     
    boolean
    contains(char key)
     
    void
    ensureCapacity(int expectedElements)
    Ensure this container can hold at least the given number of elements without resizing its buffers.
    boolean
    equals(Object obj)
     
    static CharHashSet
    from(char... elements)
    Create a set from a variable number of arguments or an array of char.
    int
    hashCode()
     
    protected int
    hashKey(char key)
    Returns a hash code for the given key.
    boolean
    indexExists(int index)
     
    char
    indexGet(int index)
    Returns the exact value of the existing key.
    void
    indexInsert(int index, char key)
    Inserts a key for an index that is not present in the set.
    int
    indexOf(char key)
    Returns a logical "index" of a given key that can be used to speed up follow-up logic in certain scenarios (conditional logic).
    void
    indexRemove(int index)
    Removes a key at an index previously acquired from indexOf(char).
    char
    indexReplace(int index, char equivalentKey)
    Replaces the existing equivalent key with the given one and returns any previous value stored for that key.
    boolean
    isEmpty()
     
    Iterator<CharCursor>
    iterator()
     
    protected int
    nextIterationSeed()
    Provides the next iteration seed used to build the iteration starting slot and offset increment.
    long
    ramBytesUsed()
    Return the memory usage of this object in bytes.
    protected void
    rehash(char[] fromKeys)
    Rehash from old buffers to new buffers.
    void
    release()
     
    boolean
    remove(char key)
    An alias for the (preferred) removeAll(org.apache.lucene.internal.hppc.CharHashSet).
    int
    removeAll(CharHashSet other)
    Removes all keys present in a given container.
    protected void
    shiftConflictingKeys(int gapSlot)
    Shift all the slot-conflicting keys allocated to (and including) slot.
    int
    size()
     
    char[]
    toArray()
     
    protected double
    verifyLoadFactor(double loadFactor)
    Validate load factor range and return it.

    Methods inherited from class java.lang.Object

    finalize, getClass, notify, notifyAll, toString, wait, wait, wait

    Methods inherited from interface org.apache.lucene.util.Accountable

    getChildResources

    Methods inherited from interface java.lang.Iterable

    forEach, spliterator

  • Field Details

    • keys

      public char[] keys
      The hash array holding keys.

    • assigned

      protected int assigned
      The number of stored keys (assigned key slots), excluding the special "empty" key, if any.
      See Also:

    • mask

      protected int mask
      Mask for slot scans in keys.

    • resizeAt

      protected int resizeAt
      Expand (rehash) keys when assigned hits this value.

    • hasEmptyKey

      protected boolean hasEmptyKey
      Special treatment for the "empty slot" key marker.

    • loadFactor

      protected double loadFactor
      The load factor for keys.

    • iterationSeed

      protected int iterationSeed
      Seed used to ensure the hash iteration order is different from an iteration to another.

  • Constructor Details

    • CharHashSet

      public CharHashSet()
      New instance with sane defaults.

    • CharHashSet

      public CharHashSet(int expectedElements)
      New instance with sane defaults.
      Parameters:
      expectedElements - The expected number of elements guaranteed not to cause a rehash (inclusive).

    • CharHashSet

      public CharHashSet(int expectedElements, double loadFactor)
      New instance with the provided defaults.
      Parameters:
      expectedElements - The expected number of elements guaranteed not to cause a rehash (inclusive).
      loadFactor - The load factor for internal buffers. Insane load factors (zero, full capacity) are rejected by verifyLoadFactor(double).

    • CharHashSet

      public CharHashSet(CharHashSet set)
      New instance copying elements from another set.

  • Method Details

    • add

      public boolean add(char key)

    • addAll

      public final int addAll(char... elements)
      Adds all elements from the given list (vararg) to this set.
      Returns:
      Returns the number of elements actually added as a result of this call (not previously present in the set).

    • addAll

      public int addAll(CharHashSet set)
      Adds all elements from the given set to this set.
      Returns:
      Returns the number of elements actually added as a result of this call (not previously present in the set).

    • addAll

      public int addAll(Iterable<? extends CharCursor> iterable)
      Adds all elements from the given iterable to this set.
      Returns:
      Returns the number of elements actually added as a result of this call (not previously present in the set).

    • toArray

      public char[] toArray()

    • remove

      public boolean remove(char key)
      An alias for the (preferred) removeAll(org.apache.lucene.internal.hppc.CharHashSet).

    • removeAll

      public int removeAll(CharHashSet other)
      Removes all keys present in a given container.
      Returns:
      Returns the number of elements actually removed as a result of this call.

    • contains

      public boolean contains(char key)

    • clear

      public void clear()

    • release

      public void release()

    • isEmpty

      public boolean isEmpty()

    • ensureCapacity

      public void ensureCapacity(int expectedElements)
      Ensure this container can hold at least the given number of elements without resizing its buffers.
      Parameters:
      expectedElements - The total number of elements, inclusive.

    • size

      public int size()

    • hashCode

      public int hashCode()
      Overrides:
      hashCode in class Object

    • equals

      public boolean equals(Object obj)
      Overrides:
      equals in class Object

    • clone

      public CharHashSet clone()
      Overrides:
      clone in class Object

    • iterator

      public Iterator<CharCursor> iterator()
      Specified by:
      iterator in interface Iterable<CharCursor>

    • ramBytesUsed

      public long ramBytesUsed()
      Description copied from interface: Accountable
      Return the memory usage of this object in bytes. Negative values are illegal.
      Specified by:
      ramBytesUsed in interface Accountable

    • nextIterationSeed

      protected int nextIterationSeed()
      Provides the next iteration seed used to build the iteration starting slot and offset increment. This method does not need to be synchronized, what matters is that each thread gets a sequence of varying seeds.

    • from

      public static CharHashSet from(char... elements)
      Create a set from a variable number of arguments or an array of char. The elements are copied from the argument to the internal buffer.

    • hashKey

      protected int hashKey(char key)
      Returns a hash code for the given key.

      The output from this function should evenly distribute keys across the entire integer range.

    • indexOf

      public int indexOf(char key)
      Returns a logical "index" of a given key that can be used to speed up follow-up logic in certain scenarios (conditional logic).

      The semantics of "indexes" are not strictly defined. Indexes may (and typically won't be) contiguous.

      The index is valid only between modifications (it will not be affected by read-only operations).

      Parameters:
      key - The key to locate in the set.
      Returns:
      A non-negative value of the logical "index" of the key in the set or a negative value if the key did not exist.
      See Also:

    • indexExists

      public boolean indexExists(int index)
      Parameters:
      index - The index of a given key, as returned from indexOf(char).
      Returns:
      Returns true if the index corresponds to an existing key or false otherwise. This is equivalent to checking whether the index is a positive value (existing keys) or a negative value (non-existing keys).
      See Also:

    • indexGet

      public char indexGet(int index)
      Returns the exact value of the existing key. This method makes sense for sets of objects which define custom key-equality relationship.
      Parameters:
      index - The index of an existing key.
      Returns:
      Returns the equivalent key currently stored in the set.
      Throws:
      AssertionError - If assertions are enabled and the index does not correspond to an existing key.
      See Also:

    • indexReplace

      public char indexReplace(int index, char equivalentKey)
      Replaces the existing equivalent key with the given one and returns any previous value stored for that key.
      Parameters:
      index - The index of an existing key.
      equivalentKey - The key to put in the set as a replacement. Must be equivalent to the key currently stored at the provided index.
      Returns:
      Returns the previous key stored in the set.
      Throws:
      AssertionError - If assertions are enabled and the index does not correspond to an existing key.
      See Also:

    • indexInsert

      public void indexInsert(int index, char key)
      Inserts a key for an index that is not present in the set. This method may help in avoiding double recalculation of the key's hash.
      Parameters:
      index - The index of a previously non-existing key, as returned from indexOf(char).
      Throws:
      AssertionError - If assertions are enabled and the index does not correspond to an existing key.
      See Also:

    • indexRemove

      public void indexRemove(int index)
      Removes a key at an index previously acquired from indexOf(char).
      Parameters:
      index - The index of the key to remove, as returned from indexOf(char).
      Throws:
      AssertionError - If assertions are enabled and the index does not correspond to an existing key.
      See Also:

    • verifyLoadFactor

      protected double verifyLoadFactor(double loadFactor)
      Validate load factor range and return it. Override and suppress if you need insane load factors.

    • rehash

      protected void rehash(char[] fromKeys)
      Rehash from old buffers to new buffers.

    • allocateBuffers

      protected void allocateBuffers(int arraySize)
      Allocate new internal buffers. This method attempts to allocate and assign internal buffers atomically (either allocations succeed or not).

    • allocateThenInsertThenRehash

      protected void allocateThenInsertThenRehash(int slot, char pendingKey)
      This method is invoked when there is a new key to be inserted into the buffer but there is not enough empty slots to do so.

      New buffers are allocated. If this succeeds, we know we can proceed with rehashing so we assign the pending element to the previous buffer (possibly violating the invariant of having at least one empty slot) and rehash all keys, substituting new buffers at the end.

    • shiftConflictingKeys

      protected void shiftConflictingKeys(int gapSlot)
      Shift all the slot-conflicting keys allocated to (and including) slot.