org.jibx.runtime.impl
Class StringIntHashMap

java.lang.Object
  extended byorg.jibx.runtime.impl.StringIntHashMap

public class StringIntHashMap
extends java.lang.Object

Hash map using String values as keys mapped to primitive int values. This implementation is unsynchronized in order to provide the best possible performance for typical usage scenarios, so explicit synchronization must be implemented by a wrapper class or directly by the application in cases where instances are modified in a multithreaded environment. The map implementation is not very efficient when resizing, but works well when the size of the map is known in advance.

Version:
1.1
Author:
Dennis M. Sosnoski

Field Summary
protected static double DEFAULT_FILL
          Default fill fraction allowed before growing table.
static int DEFAULT_NOT_FOUND
          Default value returned when key not found in table.
protected  int m_arraySize
          Size of array used for keys.
protected  int m_entryCount
          Number of entries present in table.
protected  int m_entryLimit
          Entries allowed before growing table.
protected  double m_fillFraction
          Fill fraction allowed for this hash table.
protected  int m_hitOffset
          Offset added (modulo table size) to slot number on collision.
protected  java.lang.String[] m_keyTable
          Array of key table slots.
protected  int m_notFoundValue
          Value returned when key not found in table.
protected  int[] m_valueTable
          Array of value table slots.
protected static int MINIMUM_SIZE
          Minimum size used for hash table.
 
Constructor Summary
StringIntHashMap()
          Default constructor.
StringIntHashMap(int count)
          Constructor with only size supplied.
StringIntHashMap(int count, double fill)
          Constructor with size and fill fraction specified.
StringIntHashMap(int count, double fill, int miss)
          Constructor with full specification.
StringIntHashMap(StringIntHashMap base)
          Copy (clone) constructor.
 
Method Summary
 int add(java.lang.String key, int value)
          Add an entry to the table.
private  int assignSlot(java.lang.String key, int value)
          Assign slot for entry.
 java.lang.Object clone()
          Construct a copy of the table.
 boolean containsKey(java.lang.String key)
          Check if an entry is present in the table.
private  int freeSlot(int slot)
          Find free slot number for entry.
 int get(java.lang.String key)
          Find an entry in the table.
protected  void internalRemove(int slot)
          Internal remove pair from the table.
private  boolean reinsert(int slot)
          Reinsert an entry into the hash map.
 int remove(java.lang.String key)
          Remove an entry from the table.
private  void restructure(java.lang.String[] keys, int[] values)
          Restructure the table.
private  int standardFind(java.lang.Object key)
          Standard find key in table.
private  int standardSlot(java.lang.Object key)
          Standard base slot computation for a key.
private  int stepSlot(int slot)
          Step the slot number for an entry.
 
Methods inherited from class java.lang.Object
equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Field Detail

DEFAULT_NOT_FOUND

public static final int DEFAULT_NOT_FOUND
Default value returned when key not found in table.

See Also:
Constant Field Values

DEFAULT_FILL

protected static final double DEFAULT_FILL
Default fill fraction allowed before growing table.

See Also:
Constant Field Values

MINIMUM_SIZE

protected static final int MINIMUM_SIZE
Minimum size used for hash table.

See Also:
Constant Field Values

m_fillFraction

protected final double m_fillFraction
Fill fraction allowed for this hash table.


m_entryCount

protected int m_entryCount
Number of entries present in table.


m_entryLimit

protected int m_entryLimit
Entries allowed before growing table.


m_arraySize

protected int m_arraySize
Size of array used for keys.


m_hitOffset

protected int m_hitOffset
Offset added (modulo table size) to slot number on collision.


m_keyTable

protected java.lang.String[] m_keyTable
Array of key table slots.


m_valueTable

protected int[] m_valueTable
Array of value table slots.


m_notFoundValue

protected int m_notFoundValue
Value returned when key not found in table.

Constructor Detail

StringIntHashMap

public StringIntHashMap(int count,
                        double fill,
                        int miss)
Constructor with full specification.

Parameters:
count - number of values to assume in initial sizing of table
fill - fraction full allowed for table before growing
miss - value returned when key not found in table

StringIntHashMap

public StringIntHashMap(int count,
                        double fill)
Constructor with size and fill fraction specified. Uses default hash technique and value returned when key not found in table.

Parameters:
count - number of values to assume in initial sizing of table
fill - fraction full allowed for table before growing

StringIntHashMap

public StringIntHashMap(int count)
Constructor with only size supplied. Uses default hash technique and values for fill fraction and value returned when key not found in table.

Parameters:
count - number of values to assume in initial sizing of table

StringIntHashMap

public StringIntHashMap()
Default constructor.


StringIntHashMap

public StringIntHashMap(StringIntHashMap base)
Copy (clone) constructor.

Parameters:
base - instance being copied
Method Detail

stepSlot

private final int stepSlot(int slot)
Step the slot number for an entry. Adds the collision offset (modulo the table size) to the slot number.

Parameters:
slot - slot number to be stepped
Returns:
stepped slot number

freeSlot

private final int freeSlot(int slot)
Find free slot number for entry. Starts at the slot based directly on the hashed key value. If this slot is already occupied, it adds the collision offset (modulo the table size) to the slot number and checks that slot, repeating until an unused slot is found.

Parameters:
slot - initial slot computed from key
Returns:
slot at which entry was added

standardSlot

private final int standardSlot(java.lang.Object key)
Standard base slot computation for a key.

Parameters:
key - key value to be computed
Returns:
base slot for key

standardFind

private int standardFind(java.lang.Object key)
Standard find key in table. This method may be used directly for key lookup using either the hashCode() method defined for the key objects or the System.identityHashCode() method, and either the equals() method defined for the key objects or the == operator, as selected by the hash technique constructor parameter. To implement a hash class based on some other methods of hashing and/or equality testing, define a separate method in the subclass with a different name and use that method instead. This avoids the overhead caused by overrides of a very heavily used method.

Parameters:
key - to be found in table
Returns:
index of matching key, or -index-1 of slot to be used for inserting key in table if not already present (always negative)

reinsert

private boolean reinsert(int slot)
Reinsert an entry into the hash map. This is used when the table is being directly modified, and does not adjust the count present or check the table capacity.

Parameters:
slot - position of entry to be reinserted into hash map
Returns:
true if the slot number used by the entry has has changed, false if not

internalRemove

protected void internalRemove(int slot)
Internal remove pair from the table. Removes the pair from the table by setting the key entry to null and adjusting the count present, then chains through the table to reinsert any other pairs which may have collided with the removed pair. If the associated value is an object reference, it should be set to null before this method is called.

Parameters:
slot - index number of pair to be removed

restructure

private void restructure(java.lang.String[] keys,
                         int[] values)
Restructure the table. This is used when the table is increasing or decreasing in size, and works directly with the old table representation arrays. It inserts pairs from the old arrays directly into the table without adjusting the count present or checking the table size.

Parameters:
keys - array of keys
values - array of values

assignSlot

private int assignSlot(java.lang.String key,
                       int value)
Assign slot for entry. Starts at the slot found by the hashed key value. If this slot is already occupied, it steps the slot number and checks the resulting slot, repeating until an unused slot is found. This method does not check for duplicate keys, so it should only be used for internal reordering of the tables.

Parameters:
key - to be added to table
value - associated value for key
Returns:
slot at which entry was added

add

public int add(java.lang.String key,
               int value)
Add an entry to the table. If the key is already present in the table, this replaces the existing value associated with the key.

Parameters:
key - key to be added to table (non- null)
value - associated value for key
Returns:
value previously associated with key, or reserved not found value if key not previously present in table

containsKey

public final boolean containsKey(java.lang.String key)
Check if an entry is present in the table. This method is supplied to support the use of values matching the reserved not found value.

Parameters:
key - key for entry to be found
Returns:
true if key found in table, false if not

get

public final int get(java.lang.String key)
Find an entry in the table.

Parameters:
key - key for entry to be returned
Returns:
value for key, or reserved not found value if key not found

remove

public int remove(java.lang.String key)
Remove an entry from the table. If multiple entries are present with the same key value, only the first one found will be removed.

Parameters:
key - key to be removed from table
Returns:
value associated with removed key, or reserved not found value if key not found in table

clone

public java.lang.Object clone()
Construct a copy of the table.

Returns:
shallow copy of table


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