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package jaxb1.impl.runtime;
/**
* A set of {@link Object}s that uses the == (instead of equals)
* for the comparison.
*
* @author
* Kohsuke Kawaguchi (kohsuke.kawaguchi@sun.com)
*/
final class IdentityHashSet {
/** The hash table data. */
private Object table[];
/** The total number of mappings in the hash table. */
private int count;
/**
* The table is rehashed when its size exceeds this threshold. (The
* value of this field is (int)(capacity * loadFactor).)
*/
private int threshold;
/** The load factor for the hashtable. */
private static final float loadFactor = 0.3f;
private static final int initialCapacity = 191;
public IdentityHashSet() {
table = new Object[initialCapacity];
threshold = (int) (initialCapacity * loadFactor);
}
public boolean contains(Object key) {
Object tab[] = table;
int index = (System.identityHashCode(key) & 0x7FFFFFFF) % tab.length;
while (true) {
final Object e = tab[index];
if (e == null)
return false;
if (e==key)
return true;
index = (index + 1) % tab.length;
}
}
/**
* rehash.
*
* It is possible for one thread to call get method
* while another thread is performing rehash.
* Keep this in mind.
*/
private void rehash() {
// create a new table first.
// meanwhile, other threads can safely access get method.
int oldCapacity = table.length;
Object oldMap[] = table;
int newCapacity = oldCapacity * 2 + 1;
Object newMap[] = new Object[newCapacity];
for (int i = oldCapacity; i-- > 0;)
if (oldMap[i] != null) {
int index = (System.identityHashCode(oldMap[i]) & 0x7FFFFFFF) % newMap.length;
while (newMap[index] != null)
index = (index + 1) % newMap.length;
newMap[index] = oldMap[i];
}
// threshold is not accessed by get method.
threshold = (int) (newCapacity * loadFactor);
// switch!
table = newMap;
}
public boolean add(Object newObj) {
if (count >= threshold)
rehash();
Object tab[] = table;
int index = (System.identityHashCode(newObj) & 0x7FFFFFFF) % tab.length;
Object existing;
while ((existing=tab[index]) != null) {
if(existing==newObj) return false;
index = (index + 1) % tab.length;
}
tab[index] = newObj;
count++;
return true;
}
}