A simple hashmap from keys to integers
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*
* @author Scott Ferguson
*/
/**
* The IntMap provides a simple hashmap from keys to integers. The API is
* an abbreviation of the HashMap collection API.
*
* <p>The convenience of IntMap is avoiding all the silly wrapping of
* integers.
*/
public class IntMap {
/**
* Encoding of a null entry. Since NULL is equal to Integer.MIN_VALUE,
* it's impossible to distinguish between the two.
*/
public final static int NULL = 0xdeadbeef; // Integer.MIN_VALUE + 1;
private static final Object DELETED = new Object();
private Object []_keys;
private int []_values;
private int _size;
private int _mask;
/**
* Create a new IntMap. Default size is 16.
*/
public IntMap()
{
_keys = new Object[256];
_values = new int[256];
_mask = _keys.length - 1;
_size = 0;
}
/**
* Clear the hashmap.
*/
public void clear()
{
Object []keys = _keys;
int []values = _values;
for (int i = keys.length - 1; i >= 0; i--) {
keys[i] = null;
values[i] = 0;
}
_size = 0;
}
/**
* Returns the current number of entries in the map.
*/
public int size()
{
return _size;
}
/**
* Puts a new value in the property table with the appropriate flags
*/
public int get(Object key)
{
int mask = _mask;
int hash = key.hashCode() % mask & mask;
Object []keys = _keys;
while (true) {
Object mapKey = keys[hash];
if (mapKey == null)
return NULL;
else if (mapKey == key || mapKey.equals(key))
return _values[hash];
hash = (hash + 1) % mask;
}
}
/**
* Expands the property table
*/
private void resize(int newSize)
{
Object []newKeys = new Object[newSize];
int []newValues = new int[newSize];
int mask = _mask = newKeys.length - 1;
Object []keys = _keys;
int values[] = _values;
for (int i = keys.length - 1; i >= 0; i--) {
Object key = keys[i];
if (key == null || key == DELETED)
continue;
int hash = key.hashCode() % mask & mask;
while (true) {
if (newKeys[hash] == null) {
newKeys[hash] = key;
newValues[hash] = values[i];
break;
}
hash = (hash + 1) % mask;
}
}
_keys = newKeys;
_values = newValues;
}
/**
* Puts a new value in the property table with the appropriate flags
*/
public int put(Object key, int value)
{
int mask = _mask;
int hash = key.hashCode() % mask & mask;
Object []keys = _keys;
while (true) {
Object testKey = keys[hash];
if (testKey == null || testKey == DELETED) {
keys[hash] = key;
_values[hash] = value;
_size++;
if (keys.length <= 4 * _size)
resize(4 * keys.length);
return NULL;
}
else if (key != testKey && ! key.equals(testKey)) {
hash = (hash + 1) % mask;
continue;
}
else {
int old = _values[hash];
_values[hash] = value;
return old;
}
}
}
/**
* Deletes the entry. Returns true if successful.
*/
public int remove(Object key)
{
int mask = _mask;
int hash = key.hashCode() % mask & mask;
while (true) {
Object mapKey = _keys[hash];
if (mapKey == null)
return NULL;
else if (mapKey == key) {
_keys[hash] = DELETED;
_size--;
return _values[hash];
}
hash = (hash + 1) % mask;
}
}
public String toString()
{
StringBuffer sbuf = new StringBuffer();
sbuf.append("IntMap[");
boolean isFirst = true;
for (int i = 0; i <= _mask; i++) {
if (_keys[i] != null && _keys[i] != DELETED) {
if (! isFirst)
sbuf.append(", ");
isFirst = false;
sbuf.append(_keys[i]);
sbuf.append(":");
sbuf.append(_values[i]);
}
}
sbuf.append("]");
return sbuf.toString();
}
}
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