CharsetConverter.java
/*
** Module : CharsetConverter.java
** Abstract : optimized character set conversion routines
**
** Copyright (c) 2008-2017, Golden Code Development Corporation.
**
** -#- -I- --Date-- -T- --JPRM-- ----------------Description-----------------
** 001 GES 20080730 NEW @39234 Created initial version which provides
** optimized character set conversion routines.
*/
/*
** This program is free software: you can redistribute it and/or modify
** it under the terms of the GNU Affero General Public License as
** published by the Free Software Foundation, either version 3 of the
** License, or (at your option) any later version.
**
** This program 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 Affero General Public License for more details.
**
** You may find a copy of the GNU Affero GPL version 3 at the following
** location: https://www.gnu.org/licenses/agpl-3.0.en.html
**
** Additional terms under GNU Affero GPL version 3 section 7:
**
** Under Section 7 of the GNU Affero GPL version 3, the following additional
** terms apply to the works covered under the License. These additional terms
** are non-permissive additional terms allowed under Section 7 of the GNU
** Affero GPL version 3 and may not be removed by you.
**
** 0. Attribution Requirement.
**
** You must preserve all legal notices or author attributions in the covered
** work or Appropriate Legal Notices displayed by works containing the covered
** work. You may not remove from the covered work any author or developer
** credit already included within the covered work.
**
** 1. No License To Use Trademarks.
**
** This license does not grant any license or rights to use the trademarks
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** of Golden Code Development Corporation. You are not authorized to use the
** name Golden Code, FWD, or the names of any author or contributor, for
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**
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**
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** the covered work, without written authorization.
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**
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** versions of the covered work must be marked in a reasonable way to make it
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** Corporation or FWD. All modified versions must contain the notices of
** attribution required in this license.
*/
package com.goldencode.p2j.util;
import java.io.*;
import java.util.*;
import java.nio.charset.*;
/**
* Provides optimized character set conversion routines. Currently this is
* only useful for single byte character sets.
* <p>
* This class trades use of the heap for speed by pre-calculating the
* conversions and creating conversion "tables". The resulting conversion
* operation is a simple array de-reference.
*
* @author GES
*/
public class CharsetConverter
{
/** All possible byte values. */
private static byte[] allBytes = new byte[256];
/** Simple byte to character conversion mapping. */
private char[] byteToChar = new char[256];
/** Simple character to byte conversion mapping. */
private byte[] charToByte = null;
/** Smallest character value of the character to byte mapping range. */
private int offset = 0;
static
{
for (int i = 0; i < 256; i++)
{
allBytes[i] = (byte) i;
}
}
/**
* Create an instance that converts between Unicode and the given
* character set.
*
* @param cset
* The character set.
*/
public CharsetConverter(String cset)
{
try
{
// prepare our byte to character conversion mapping
String txt = (cset == null) ? new String(allBytes)
: new String(allBytes, cset);
int min = 64 * 1024;
int max = 0;
int len = 0;
for (int i = 0; i < 256; i++)
{
char ch = txt.charAt(i);
min = Math.min(min, ch);
max = Math.max(max, ch);
byteToChar[i] = ch;
}
offset = min;
len = max - min + 1;
charToByte = new byte[len];
Arrays.fill(charToByte, (byte) -1);
for (int i = 0; i < 256; i++)
{
char ch = txt.charAt(i);
charToByte[ch - offset] = (byte) i;
}
}
catch (UnsupportedEncodingException uee)
{
// we can't map this, ensure that an error will be returned
Arrays.fill(byteToChar, (char) -1);
}
}
/**
* Convert the given Unicode character into the corresponding number in
* the represented character set.
*
* @param ch
* The Unicode character to convert.
*
* @return The number represented or -1 if there is any error.
*/
public int toInt(char ch)
{
return charToByte[ch - offset] & 0x000000FF;
}
/**
* Convert the given Unicode character into the corresponding number in
* the represented character set.
*
* @param ch
* The Unicode character to convert.
*
* @return The number represented or -1 if there is any error.
*/
public byte toByte(char ch)
{
return charToByte[ch - offset];
}
/**
* Convert the given number into the corresponding Unicode character in
* the represented character set.
*
* @param i
* The number to convert.
*
* @return The Unicode character representing the given number or -1
* if there is any error.
*/
public char toChar(int i)
{
return byteToChar[i];
}
/**
* Convert the given byte into the corresponding Unicode character in
* the represented character set.
*
* @param b
* The byte to convert.
*
* @return The Unicode character representing the given byte or -1
* if there is any error.
*/
public char toChar(byte b)
{
return byteToChar[b];
}
}