/**
* @author : Paul Taylor
* @author : Eric Farng
*
* Version @version:$Id: NumberVariableLength.java 836 2009-11-12 15:44:07Z paultaylor $
*
* MusicTag Copyright (C)2003,2004
*
* This library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser
* General Public License as published by the Free Software Foundation; either version 2.1 of the License,
* or (at your option) any later version.
*
* This library 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License along with this library; if not,
* you can get a copy from http://www.opensource.org/licenses/lgpl-license.php or write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* Description:
*
*/
package org.jaudiotagger.tag.datatype;
import org.jaudiotagger.tag.InvalidDataTypeException;
import org.jaudiotagger.tag.id3.AbstractTagFrameBody;
import org.jaudiotagger.tag.id3.ID3Tags;
/**
* Represents a number which may span a number of bytes when written to file depending what size is to be represented.
* <p/>
* The bitorder in ID3v2 is most significant bit first (MSB). The byteorder in multibyte numbers is most significant
* byte first (e.g. $12345678 would be encoded $12 34 56 78), also known as big endian and network byte order.
* <p/>
* In ID3Specification would be denoted as $xx xx xx xx (xx ...) , this denotes at least four bytes but may be more.
* Sometimes may be completely optional (zero bytes)
*/
public class NumberVariableLength extends AbstractDataType {
private static final int MINIMUM_NO_OF_DIGITS = 1;
private static final int MAXIMUM_NO_OF_DIGITS = 8;
int minLength = MINIMUM_NO_OF_DIGITS;
/**
* Creates a new ObjectNumberVariableLength datatype, set minimum length to zero
* if this datatype is optional.
*
* @param identifier
* @param frameBody
* @param minimumSize
*/
public NumberVariableLength(String identifier, AbstractTagFrameBody frameBody, int minimumSize) {
super(identifier, frameBody);
//Set minimum length, which can be zero if optional
this.minLength = minimumSize;
}
public NumberVariableLength(NumberVariableLength copy) {
super(copy);
this.minLength = copy.minLength;
}
/**
* Return the maximum number of digits that can be used to express the number
*
* @return the maximum number of digits that can be used to express the number
*/
public int getMaximumLenth() {
return MAXIMUM_NO_OF_DIGITS;
}
/**
* Return the minimum number of digits that can be used to express the number
*
* @return the minimum number of digits that can be used to express the number
*/
public int getMinimumLength() {
return minLength;
}
/**
* @param minimumSize
*/
public void setMinimumSize(int minimumSize) {
if (minimumSize > 0) {
this.minLength = minimumSize;
}
}
/**
* @return the number of bytes required to write this to a file
*/
public int getSize() {
if (value == null) {
return 0;
} else {
int current;
long temp = ID3Tags.getWholeNumber(value);
int size = 0;
for (int i = MINIMUM_NO_OF_DIGITS; i <= MAXIMUM_NO_OF_DIGITS; i++) {
current = (byte) temp & 0xFF;
if (current != 0) {
size = i;
}
temp >>= MAXIMUM_NO_OF_DIGITS;
}
return (minLength > size) ? minLength : size;
}
}
/**
* @param obj
* @return
*/
public boolean equals(Object obj) {
if (!(obj instanceof NumberVariableLength)) {
return false;
}
NumberVariableLength object = (NumberVariableLength) obj;
return this.minLength == object.minLength && super.equals(obj);
}
/**
* Read from Byte Array
*
* @param arr
* @param offset
* @throws NullPointerException
* @throws IndexOutOfBoundsException
*/
public void readByteArray(byte[] arr, int offset) throws InvalidDataTypeException {
//Coding error, should never happen
if (arr == null) {
throw new NullPointerException("Byte array is null");
}
//Coding error, should never happen as far as I can see
if (offset < 0) {
throw new IllegalArgumentException("negativer offset into an array offset:" + offset);
}
//If optional then set value to zero, this will mean that if this frame is written back to file it will be created
//with this additional datatype wheras it didnt exist but I think this is probably an advantage the frame is
//more likely to be parsed by other applications if it contains optional fields.
//if not optional problem with this frame
if (offset >= arr.length) {
if (minLength == 0) {
value = (long) 0;
return;
} else {
throw new InvalidDataTypeException("Offset to byte array is out of bounds: offset = " + offset + ", array.length = " + arr.length);
}
}
long lvalue = 0;
//Read the bytes (starting from offset), the most significant byte of the number being constructed is read first,
//we then shift the resulting long one byte over to make room for the next byte
for (int i = offset; i < arr.length; i++) {
lvalue <<= 8;
lvalue += (arr[i] & 0xff);
}
value = lvalue;
}
/**
* @return String representation of the number
*/
public String toString() {
if (value == null) {
return "";
} else {
return value.toString();
}
}
/**
* Write to Byte Array
*
* @return the datatype converted to a byte array
*/
public byte[] writeByteArray() {
int size = getSize();
byte[] arr;
if (size == 0) {
arr = new byte[0];
} else {
long temp = ID3Tags.getWholeNumber(value);
arr = new byte[size];
//keeps shifting the number downwards and masking the last 8 bist to get the value for the next byte
//to be written
for (int i = size - 1; i >= 0; i--) {
arr[i] = (byte) (temp & 0xFF);
temp >>= 8;
}
}
return arr;
}
}