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Java example source code file (CompactByteArray.java)
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The CompactByteArray.java Java example source code
/*
* Copyright (c) 1996, 2011, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
/*
* (C) Copyright Taligent, Inc. 1996 - All Rights Reserved
* (C) Copyright IBM Corp. 1996 - All Rights Reserved
*
* The original version of this source code and documentation is copyrighted
* and owned by Taligent, Inc., a wholly-owned subsidiary of IBM. These
* materials are provided under terms of a License Agreement between Taligent
* and Sun. This technology is protected by multiple US and International
* patents. This notice and attribution to Taligent may not be removed.
* Taligent is a registered trademark of Taligent, Inc.
*
*/
package sun.text;
/**
* class CompactATypeArray : use only on primitive data types
* Provides a compact way to store information that is indexed by Unicode
* values, such as character properties, types, keyboard values, etc.This
* is very useful when you have a block of Unicode data that contains
* significant values while the rest of the Unicode data is unused in the
* application or when you have a lot of redundance, such as where all 21,000
* Han ideographs have the same value. However, lookup is much faster than a
* hash table.
* A compact array of any primitive data type serves two purposes:
* <UL type = round>
* <LI>Fast access of the indexed values.
* <LI>Smaller memory footprint.
* </UL>
* A compact array is composed of a index array and value array. The index
* array contains the indicies of Unicode characters to the value array.
*
* @see CompactIntArray
* @see CompactShortArray
* @author Helena Shih
*/
public final class CompactByteArray implements Cloneable {
/**
* The total number of Unicode characters.
*/
public static final int UNICODECOUNT =65536;
/**
* Constructor for CompactByteArray.
* @param defaultValue the default value of the compact array.
*/
public CompactByteArray(byte defaultValue)
{
int i;
values = new byte[UNICODECOUNT];
indices = new short[INDEXCOUNT];
hashes = new int[INDEXCOUNT];
for (i = 0; i < UNICODECOUNT; ++i) {
values[i] = defaultValue;
}
for (i = 0; i < INDEXCOUNT; ++i) {
indices[i] = (short)(i< BLOCKSHIFT] & 0xFFFF)
+ (index & BLOCKMASK)]);
}
/**
* Set a new value for a Unicode character.
* Set automatically expands the array if it is compacted.
* @param index the character to set the mapped value with
* @param value the new mapped value
*/
public void setElementAt(char index, byte value)
{
if (isCompact)
expand();
values[(int)index] = value;
touchBlock(index >> BLOCKSHIFT, value);
}
/**
* Set new values for a range of Unicode character.
* @param start the starting offset o of the range
* @param end the ending offset of the range
* @param value the new mapped value
*/
public void setElementAt(char start, char end, byte value)
{
int i;
if (isCompact) {
expand();
}
for (i = start; i <= end; ++i) {
values[i] = value;
touchBlock(i >> BLOCKSHIFT, value);
}
}
/**
*Compact the array.
*/
public void compact()
{
if (!isCompact) {
int limitCompacted = 0;
int iBlockStart = 0;
short iUntouched = -1;
for (int i = 0; i < indices.length; ++i, iBlockStart += BLOCKCOUNT) {
indices[i] = -1;
boolean touched = blockTouched(i);
if (!touched && iUntouched != -1) {
// If no values in this block were set, we can just set its
// index to be the same as some other block with no values
// set, assuming we've seen one yet.
indices[i] = iUntouched;
} else {
int jBlockStart = 0;
int j = 0;
for (j = 0; j < limitCompacted;
++j, jBlockStart += BLOCKCOUNT) {
if (hashes[i] == hashes[j] &&
arrayRegionMatches(values, iBlockStart,
values, jBlockStart, BLOCKCOUNT)) {
indices[i] = (short)jBlockStart;
break;
}
}
if (indices[i] == -1) {
// we didn't match, so copy & update
System.arraycopy(values, iBlockStart,
values, jBlockStart, BLOCKCOUNT);
indices[i] = (short)jBlockStart;
hashes[j] = hashes[i];
++limitCompacted;
if (!touched) {
// If this is the first untouched block we've seen,
// remember its index.
iUntouched = (short)jBlockStart;
}
}
}
}
// we are done compacting, so now make the array shorter
int newSize = limitCompacted*BLOCKCOUNT;
byte[] result = new byte[newSize];
System.arraycopy(values, 0, result, 0, newSize);
values = result;
isCompact = true;
hashes = null;
}
}
/**
* Convenience utility to compare two arrays of doubles.
* @param len the length to compare.
* The start indices and start+len must be valid.
*/
final static boolean arrayRegionMatches(byte[] source, int sourceStart,
byte[] target, int targetStart,
int len)
{
int sourceEnd = sourceStart + len;
int delta = targetStart - sourceStart;
for (int i = sourceStart; i < sourceEnd; i++) {
if (source[i] != target[i + delta])
return false;
}
return true;
}
/**
* Remember that a specified block was "touched", i.e. had a value set.
* Untouched blocks can be skipped when compacting the array
*/
private final void touchBlock(int i, int value) {
hashes[i] = (hashes[i] + (value<<1)) | 1;
}
/**
* Query whether a specified block was "touched", i.e. had a value set.
* Untouched blocks can be skipped when compacting the array
*/
private final boolean blockTouched(int i) {
return hashes[i] != 0;
}
/** For internal use only. Do not modify the result, the behavior of
* modified results are undefined.
*/
public short getIndexArray()[]
{
return indices;
}
/** For internal use only. Do not modify the result, the behavior of
* modified results are undefined.
*/
public byte getStringArray()[]
{
return values;
}
/**
* Overrides Cloneable
*/
public Object clone()
{
try {
CompactByteArray other = (CompactByteArray) super.clone();
other.values = values.clone();
other.indices = indices.clone();
if (hashes != null) other.hashes = hashes.clone();
return other;
} catch (CloneNotSupportedException e) {
throw new InternalError(e);
}
}
/**
* Compares the equality of two compact array objects.
* @param obj the compact array object to be compared with this.
* @return true if the current compact array object is the same
* as the compact array object obj; false otherwise.
*/
public boolean equals(Object obj) {
if (obj == null) return false;
if (this == obj) // quick check
return true;
if (getClass() != obj.getClass()) // same class?
return false;
CompactByteArray other = (CompactByteArray) obj;
for (int i = 0; i < UNICODECOUNT; i++) {
// could be sped up later
if (elementAt((char)i) != other.elementAt((char)i))
return false;
}
return true; // we made it through the guantlet.
}
/**
* Generates the hash code for the compact array object
*/
public int hashCode() {
int result = 0;
int increment = Math.min(3, values.length/16);
for (int i = 0; i < values.length; i+= increment) {
result = result * 37 + values[i];
}
return result;
}
// --------------------------------------------------------------
// package private
// --------------------------------------------------------------
/**
* Expanding takes the array back to a 65536 element array.
*/
private void expand()
{
int i;
if (isCompact) {
byte[] tempArray;
hashes = new int[INDEXCOUNT];
tempArray = new byte[UNICODECOUNT];
for (i = 0; i < UNICODECOUNT; ++i) {
byte value = elementAt((char)i);
tempArray[i] = value;
touchBlock(i >> BLOCKSHIFT, value);
}
for (i = 0; i < INDEXCOUNT; ++i) {
indices[i] = (short)(i<
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