/*
* Created on 1-Jan-2004
*
* Copyright (C)2004 Paul Grebenc
*
* 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, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* $Id: ID3DataInputStream.java,v 1.3 2005/02/06 18:11:25 paul Exp $
*/
package org.blinkenlights.jid3.io;
import java.io.*;
import org.blinkenlights.jid3.*;
/**
* @author paul
*
* Custom DataInputStream containing convenience methods for reading ID3 tags.
*
*/
public class ID3DataInputStream extends DataInputStream
{
public ID3DataInputStream(InputStream oIS)
{
super(oIS);
}
/** Reads an unsigned big-endian 16-bit value and returns an int.
* @return the integer value read
* @throws IOException
*/
public final int readBEUnsigned16()
throws IOException
{
int iHi = readUnsignedByte();
int iLo = readUnsignedByte();
int iVal = iLo | (iHi << 8);
return iVal;
}
/** Read an unsigned big-endian 24-bit value and returns an int.
*
* @return the integer value read
* @throws IOException
*/
public int readBE24()
throws IOException
{
int iThree = readUnsignedByte();
int iTwo = readUnsignedByte();
int iOne = readUnsignedByte();
int iVal = (iOne | (iTwo << 8) | (iThree << 16));
return iVal;
}
/** Read a signed big-endian 32-bit value and returns an int.
*
* @return the integer value read
* @throws IOException
*/
public int readBE32()
throws IOException
{
int iFour = readUnsignedByte();
int iThree = readUnsignedByte();
int iTwo = readUnsignedByte();
int iOne = readUnsignedByte();
int iVal = (iOne | (iTwo << 8) | (iThree << 16) | (iFour << 24));
return iVal;
}
/** Read an unsigned big-endian 32-bit value and returns a long.
*
* @return the long value read
* @throws IOException
*/
public long readUnsignedBE32()
throws IOException
{
long lFour = readUnsignedByte();
long lThree = readUnsignedByte();
long lTwo = readUnsignedByte();
long lOne = readUnsignedByte();
long lVal = (lOne | (lTwo << 8) | (lThree << 16) | (lFour << 24));
return lVal;
}
/** Read an encoded four byte value.
* The encoding method uses only the lowest seven bits of each byte, to prevent synchronization
* errors in the MP3 data stream.
*/
public int readID3Four()
throws IOException, ID3Exception
{
int iValue = 0;
byte[] abyValue = new byte[4];
readFully(abyValue);
if ( ((abyValue[0] & 0x80) != 0) ||
((abyValue[1] & 0x80) != 0) ||
((abyValue[2] & 0x80) != 0) ||
((abyValue[3] & 0x80) != 0) )
{
throw new ID3Exception("High bit cannot be set in encoded values.");
}
iValue |= ((abyValue[0] & 0x7f) << (3 * 7));
iValue |= ((abyValue[1] & 0x7f) << (2 * 7));
iValue |= ((abyValue[2] & 0x7f) << (1 * 7));
iValue |= ((abyValue[3] & 0x7f) << (0 * 7));
return iValue;
}
/** Read an ISO-8859-1 encoded string to null.
*
* @return a String, or null if string would be zero length
* @throws IOException
*/
public String readStringToNull()
throws IOException
{
return readStringToNull(Integer.MAX_VALUE);
}
/** Read an ISO-8859-1 string to null, not exceeding a predefined length.
*
* @param iMaxLength a length beyond which not to read further
* @return a String, or null if string would be zero length
* @throws IOException on I/O error, or if string would exceed allowed length
*/
public String readStringToNull(int iMaxLength)
throws IOException
{
ByteArrayOutputStream oStringBAOS = new ByteArrayOutputStream();
int iStringByte;
do
{
iStringByte = readUnsignedByte();
if (iStringByte != 0)
{
if (oStringBAOS.size() == iMaxLength)
{
throw new IOException("String length exceeds set " + iMaxLength + " byte limit.");
}
oStringBAOS.write(iStringByte);
}
}
while (iStringByte != 0);
// return byte array as a string
byte[] abyShortDescription = oStringBAOS.toByteArray();
return new String(abyShortDescription);
}
/** Read a string in the specified encoding format to null. Note that Unicode strings must be terminated by
* a double null (two zero bytes).
*
* @param oTextEncoding the encoding format of the string to be read
* @return a String, or null if string would be zero length
* @throws IOException
*/
public String readStringToNull(TextEncoding oTextEncoding)
throws IOException
{
return readStringToNull(oTextEncoding, Integer.MAX_VALUE);
}
/** Read a string in the specified encoding format to null, not exceeding a predefined length. Note that
* Unicode strings must be terminated by a double null (two zero bytes).
*
* @param oTextEncoding the encoding format of the string to be read
* @param iMaxLength a length beyond which not to read further (in characters, not necessarily bytes)
* @return a String, or null if string would be zero length
* @throws IOException on I/O error, or if string would exceed allowed length
*/
public String readStringToNull(TextEncoding oTextEncoding, int iMaxLength)
throws IOException
{
if (oTextEncoding == null)
{
throw new NullPointerException("Text encoding cannot be null.");
}
ByteArrayOutputStream oStringBAOS = new ByteArrayOutputStream();
int iStringByte1;
int iStringByte2 = 0;
int iLength = 0;
do
{
iStringByte1 = readUnsignedByte();
if (oTextEncoding.equals(TextEncoding.UNICODE))
{
iStringByte2 = readUnsignedByte();
}
if ((iStringByte1 != 0) || (iStringByte2 != 0))
{
if (iLength == iMaxLength)
{
throw new IOException("String length exceeds set " + iMaxLength + " byte limit.");
}
oStringBAOS.write(iStringByte1);
if (oTextEncoding.equals(TextEncoding.UNICODE))
{
oStringBAOS.write(iStringByte2);
}
iLength++;
}
}
while ((iStringByte1 != 0) || (iStringByte2 != 0)) ;
// return byte array as a string
byte[] abyShortDescription = oStringBAOS.toByteArray();
return new String(abyShortDescription, oTextEncoding.getEncodingString());
}
}
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