index point to the "first"
- * index which is not empty. If such does not exist (eg. the map is
- * empty) it would be zero.
- */
- public IndexIterator() {
- for (baseHashIndex = 0; baseHashIndex < baseHash.length; ++baseHashIndex) {
- index = baseHash[baseHashIndex];
- if (index != 0) {
- break;
- }
- }
- }
-
- public boolean hasNext() {
- return (index != 0);
- }
-
- public int next() {
- // Save the last index visited
- lastIndex = index;
-
- // next the index
- index = next[index];
-
- // if the next index points to the 'Ground' it means we're done with
- // the current hash entry and we need to jump to the next one. This
- // is done until all the hash entries had been visited.
- while (index == 0 && ++baseHashIndex < baseHash.length) {
- index = baseHash[baseHashIndex];
- }
-
- return lastIndex;
- }
-
- public void remove() {
- IntHashSet.this.remove(keys[lastIndex]);
- }
-
- }
-
- /**
- * Implements an IntIterator, used for iteration over the map's keys.
- */
- private final class KeyIterator implements IntIterator {
- private IntIterator iterator = new IndexIterator();
-
- KeyIterator() { }
-
- public boolean hasNext() {
- return iterator.hasNext();
- }
-
- public int next() {
- return keys[iterator.next()];
- }
-
- public void remove() {
- iterator.remove();
- }
- }
-
- /**
- * Default capacity - in case no capacity was specified in the constructor
- */
- private static int defaultCapacity = 16;
-
- /**
- * Holds the base hash entries. if the capacity is 2^N, than the base hash
- * holds 2^(N+1). It can hold
- */
- int[] baseHash;
-
- /**
- * The current capacity of the map. Always 2^N and never less than 16. We
- * never use the zero index. It is needed to improve performance and is also
- * used as "ground".
- */
- private int capacity;
-
- /**
- * All objects are being allocated at map creation. Those objects are "free"
- * or empty. Whenever a new pair comes along, a pair is being "allocated" or
- * taken from the free-linked list. as this is just a free list.
- */
- private int firstEmpty;
-
- /**
- * hashFactor is always (2^(N+1)) - 1. Used for faster hashing.
- */
- private int hashFactor;
-
- /**
- * This array holds the unique keys
- */
- int[] keys;
-
- /**
- * In case of collisions, we implement a double linked list of the colliding
- * hash's with the following next[] and prev[]. Those are also used to store
- * the "empty" list.
- */
- int[] next;
-
- private int prev;
-
- /**
- * Number of currently objects in the map.
- */
- private int size;
-
- /**
- * Constructs a map with default capacity.
- */
- public IntHashSet() {
- this(defaultCapacity);
- }
-
- /**
- * Constructs a map with given capacity. Capacity is adjusted to a native
- * power of 2, with minimum of 16.
- *
- * @param capacity
- * minimum capacity for the map.
- */
- public IntHashSet(int capacity) {
- this.capacity = 16;
- // Minimum capacity is 16..
- while (this.capacity < capacity) {
- // Multiply by 2 as long as we're still under the requested capacity
- this.capacity <<= 1;
- }
-
- // As mentioned, we use the first index (0) as 'Ground', so we need the
- // length of the arrays to be one more than the capacity
- int arrayLength = this.capacity + 1;
-
- this.keys = new int[arrayLength];
- this.next = new int[arrayLength];
-
- // Hash entries are twice as big as the capacity.
- int baseHashSize = this.capacity << 1;
-
- this.baseHash = new int[baseHashSize];
-
- // The has factor is 2^M - 1 which is used as an "AND" hashing operator.
- // {@link #calcBaseHash()}
- this.hashFactor = baseHashSize - 1;
-
- this.size = 0;
-
- clear();
- }
-
- /**
- * Adds a pair to the map. Takes the first empty position from the
- * empty-linked-list's head - {@link firstEmpty}.
- *
- * New pairs are always inserted to baseHash, and are followed by the old
- * colliding pair.
- *
- * @param key
- * integer which maps the given value
- * @param e
- * value which is being mapped using the given key
- */
- private void prvt_add(int key) {
- // Hash entry to which the new pair would be inserted
- int hashIndex = calcBaseHashIndex(key);
-
- // 'Allocating' a pair from the "Empty" list.
- int objectIndex = firstEmpty;
-
- // Setting data
- firstEmpty = next[firstEmpty];
- keys[objectIndex] = key;
-
- // Inserting the new pair as the first node in the specific hash entry
- next[objectIndex] = baseHash[hashIndex];
- baseHash[hashIndex] = objectIndex;
-
- // Announcing a new pair was added!
- ++size;
- }
-
- /**
- * Calculating the baseHash index using the internal hashFactor
- * .
- *
- * @param key
- */
- protected int calcBaseHashIndex(int key) {
- return key & hashFactor;
- }
-
- /**
- * Empties the map. Generates the "Empty" space list for later allocation.
- */
- public void clear() {
- // Clears the hash entries
- Arrays.fill(this.baseHash, 0);
-
- // Set size to zero
- size = 0;
-
- // Mark all array entries as empty. This is done with
- // firstEmpty pointing to the first valid index (1 as 0 is
- // used as 'Ground').
- firstEmpty = 1;
-
- // And setting all the next[i] to point at
- // i+1.
- for (int i = 1; i < this.capacity;) {
- next[i] = ++i;
- }
-
- // Surly, the last one should point to the 'Ground'.
- next[this.capacity] = 0;
- }
-
- /**
- * Checks if a given key exists in the map.
- *
- * @param value
- * that is checked against the map data.
- * @return true if the key exists in the map. false otherwise.
- */
- public boolean contains(int value) {
- return find(value) != 0;
- }
-
- /**
- * Find the actual index of a given key.
- *
- * @param key
- * @return index of the key. zero if the key wasn't found.
- */
- protected int find(int key) {
- // Calculate the hash entry.
- int baseHashIndex = calcBaseHashIndex(key);
-
- // Start from the hash entry.
- int localIndex = baseHash[baseHashIndex];
-
- // while the index does not point to the 'Ground'
- while (localIndex != 0) {
- // returns the index found in case of of a matching key.
- if (keys[localIndex] == key) {
- return localIndex;
- }
-
- // next the local index
- localIndex = next[localIndex];
- }
-
- // If we got this far, it could only mean we did not find the key we
- // were asked for. return 'Ground' index.
- return 0;
- }
-
- /**
- * Find the actual index of a given key with it's baseHashIndex.- * If the key was already inside just - * updating the value it refers to as the given object. - *
- * Otherwise if the map is full, first {@link #grow()} the map.
- *
- * @param value
- * integer which maps the given value
- * @return true always.
- */
- public boolean add(int value) {
- // Does key exists?
- int index = find(value);
-
- // Yes!
- if (index != 0) {
- return true;
- }
-
- // Is there enough room for a new pair?
- if (size == capacity) {
- // No? Than grow up!
- grow();
- }
-
- // Now that everything is set, the pair can be just put inside with no
- // worries.
- prvt_add(value);
-
- return true;
- }
-
- /**
- * Remove a pair from the map, specified by it's key.
- *
- * @param value
- * specify the value to be removed
- *
- * @return true if the map was changed (the key was found and removed).
- * false otherwise.
- */
- public boolean remove(int value) {
- int baseHashIndex = calcBaseHashIndex(value);
- int index = findForRemove(value, baseHashIndex);
- if (index != 0) {
- // If it is the first in the collision list, we should promote its
- // next colliding element.
- if (prev == 0) {
- baseHash[baseHashIndex] = next[index];
- }
-
- next[prev] = next[index];
- next[index] = firstEmpty;
- firstEmpty = index;
- --size;
- return true;
- }
-
- return false;
- }
-
- /**
- * @return number of pairs currently in the map
- */
- public int size() {
- return this.size;
- }
-
- /**
- * Translates the mapped pairs' values into an array of Objects
- *
- * @return an object array of all the values currently in the map.
- */
- public int[] toArray() {
- int j = -1;
- int[] array = new int[size];
-
- // Iterates over the values, adding them to the array.
- for (IntIterator iterator = iterator(); iterator.hasNext();) {
- array[++j] = iterator.next();
- }
- return array;
- }
-
- /**
- * Translates the mapped pairs' values into an array of ints
- *
- * @param a
- * the array into which the elements of the map are to be stored,
- * if it is big enough; otherwise, a new array of the same
- * runtime type is allocated for this purpose.
- *
- * @return an array containing the values stored in the map
- *
- */
- public int[] toArray(int[] a) {
- int j = 0;
- if (a.length < size) {
- a = new int[size];
- }
- // Iterates over the values, adding them to the array.
- for (IntIterator iterator = iterator(); j < a.length
- && iterator.hasNext(); ++j) {
- a[j] = iterator.next();
- }
- return a;
- }
-
- /**
- * I have no idea why would anyone call it - but for debug purposes.
- * Prints the entire map, including the index, key, object, next and prev.
- */
- @Override
- public String toString() {
- StringBuffer sb = new StringBuffer();
- sb.append('{');
- IntIterator iterator = iterator();
- while (iterator.hasNext()) {
- sb.append(iterator.next());
- if (iterator.hasNext()) {
- sb.append(',');
- sb.append(' ');
- }
- }
- sb.append('}');
- return sb.toString();
- }
-
- public String toHashString() {
- String string = "\n";
- StringBuffer sb = new StringBuffer();
-
- for (int i = 0; i < this.baseHash.length; i++) {
- StringBuffer sb2 = new StringBuffer();
- boolean shouldAppend = false;
- sb2.append(i + ".\t");
- for (int index = baseHash[i]; index != 0; index = next[index]) {
- sb2.append(" -> " + keys[index] + "@" + index);
- shouldAppend = true;
- }
- if (shouldAppend) {
- sb.append(sb2);
- sb.append(string);
- }
- }
-
- return sb.toString();
- }
-}
\ No newline at end of file