Class CharHashSet

  • All Implemented Interfaces:
    java.lang.Cloneable, java.lang.Iterable<CharCursor>, Accountable

    public class CharHashSet
    extends java.lang.Object
    implements java.lang.Iterable<CharCursor>, Accountable, java.lang.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

    • 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.
      private static long BASE_RAM_BYTES_USED  
      private static char EMPTY_KEY  
      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.
    • 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

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      boolean add​(char key)  
      int addAll​(char... elements)
      Adds all elements from the given list (vararg) to this set.
      int addAll​(java.lang.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​(java.lang.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()  
      java.util.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)
      int removeAll​(CharHashSet other)
      Removes all keys present in a given container.
      private boolean sameKeys​(CharHashSet other)
      Return true if all keys of some other container exist in this 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 java.lang.Iterable

        forEach, spliterator
    • Field Detail

      • BASE_RAM_BYTES_USED

        private static final long BASE_RAM_BYTES_USED
      • 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:
        size(), hasEmptyKey
      • 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 Detail

      • 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 Detail

      • 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​(java.lang.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()
      • 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 java.lang.Object
      • equals

        public boolean equals​(java.lang.Object obj)
        Overrides:
        equals in class java.lang.Object
      • sameKeys

        private boolean sameKeys​(CharHashSet other)
        Return true if all keys of some other container exist in this container.
      • clone

        public CharHashSet clone()
        Overrides:
        clone in class java.lang.Object
      • iterator

        public java.util.Iterator<CharCursor> iterator()
        Specified by:
        iterator in interface java.lang.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(int), indexGet(int), indexInsert(int, char), indexReplace(int, char)
      • 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:
        indexOf(char)
      • 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:
        java.lang.AssertionError - If assertions are enabled and the index does not correspond to an existing key.
        See Also:
        indexOf(char)
      • 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:
        java.lang.AssertionError - If assertions are enabled and the index does not correspond to an existing key.
        See Also:
        indexOf(char)
      • 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:
        java.lang.AssertionError - If assertions are enabled and the index does not correspond to an existing key.
        See Also:
        indexOf(char)
      • 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:
        java.lang.AssertionError - If assertions are enabled and the index does not correspond to an existing key.
        See Also:
        indexOf(char)
      • 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.