id3v2tag.java

java声音播放管理

     * instead of increasing the size of the file.  That is only if there is 
     * a sufficient amount of padding for the updated tag.
     *
     * @return the new amount of padding
     */
    private int getUpdatedPadding() {
	int curSize = getSize();
	int pad = 0;

	if( (origPadding == padding) && (curSize > origSize) && 
	     (padding >= (curSize - origSize)) ) {

	    pad = padding - (curSize - origSize);
	}
	else if( curSize < origSize ) {
	    pad = (origSize - curSize) + padding;
	}	

	return pad;
    }

    /**
     * Set the data contained in a text frame.  This includes all frames with
     * an id that starts with 'T' but excludes "TXXX".  If an improper id
     * is passed, then nothing will happen.
     *
     * @param id the id of the frame to set the data for
     * @param data the data for the frame
     */
    public void setTextFrame( String id, String data ) {
	if( (id.charAt(0) == 'T') && 
	    !id.equals(ID3v2Frames.USER_DEFINED_TEXT_INFO) ) {

	    try {
		byte[] b = new byte[data.length() + 1];
		b[0] = 0;
		System.arraycopy( data.getBytes( ENC_TYPE ), 0, b, 1, 
				  data.length() );

		updateFrameData( id, b );
	    }
	    catch( UnsupportedEncodingException e ) {
		e.printStackTrace();
	    }
	}
    }

    /**
     * Set the data contained in a URL frame.  This includes all frames with
     * an id that starts with 'W' but excludes "WXXX".  If an improper id is
     * passed, then nothing will happen.
     *
     * @param id the id of the frame to set the data for
     * @param data the data for the frame
     */
    public void setURLFrame( String id, String data ) {
	if( (id.charAt(0) == 'W') && 
	    !id.equals(ID3v2Frames.USER_DEFINED_URL) ) {
	    
	    updateFrameData( id, data.getBytes() );
	}	
    }

    /**
     * Sets the data contained in the user defined text frame (TXXX).
     *
     * @param description a description of the data
     * @param value the data for the frame
     */
    public void setUserDefinedTextFrame( String description, String value ) {
	try {
	    byte[] b = new byte[description.length() + value.length() + 2];
	    int bytesCopied = 0;
	    b[bytesCopied++] = 0;
	    System.arraycopy( description.getBytes(ENC_TYPE), 0, b, 
			      bytesCopied, description.length() );
	    bytesCopied += description.length();
	    b[bytesCopied++] = 0;
	    System.arraycopy( value.getBytes(ENC_TYPE), 0, b, bytesCopied,
			      value.length() );
	    bytesCopied += value.length();

	    updateFrameData( ID3v2Frames.USER_DEFINED_TEXT_INFO, b );
	}
	catch( UnsupportedEncodingException e ) {
	    e.printStackTrace();
	}
    }

    /**
     * Sets the data contained in the user defined url frame (WXXX).
     *
     * @param description a description of the url
     * @param value the url for the frame
     */
    public void setUserDefinedURLFrame( String description, String value ) {
	try {
	    byte[] b = new byte[description.length() + value.length() + 2];
	    int bytesCopied = 0;
	    b[bytesCopied++] = 0;
	    System.arraycopy( description.getBytes(ENC_TYPE), 0, b, 
			      bytesCopied, description.length() );
	    bytesCopied += description.length();
	    b[bytesCopied++] = 0;
	    System.arraycopy( value.getBytes(), 0, b, bytesCopied,
			      value.length() );
	    bytesCopied += value.length();
	    
	    updateFrameData( ID3v2Frames.USER_DEFINED_URL, b );
	}
	catch( UnsupportedEncodingException e ) {
	    e.printStackTrace();
	}
    }

    /**
     * Set the data contained in the comments frame (COMM).
     *
     * @param description a description of the comment
     * @param comment the comment
     */
    public void setCommentFrame( String description, String comment ) {
	try {
	    byte[] b = new byte[description.length() + comment.length() + 5];
	    int bytesCopied = 0;
	    b[bytesCopied++] = 0;
	    b[bytesCopied++] = 'e';
	    b[bytesCopied++] = 'n';
	    b[bytesCopied++] = 'g';
	    System.arraycopy( description.getBytes(ENC_TYPE), 0, b, 
			      bytesCopied, description.length() );
	    bytesCopied += description.length();
	    b[bytesCopied++] = 0;
	    System.arraycopy( comment.getBytes(ENC_TYPE), 0, b,
			      bytesCopied, comment.length() );
	    bytesCopied += comment.length();
	    
	    updateFrameData( ID3v2Frames.COMMENTS, b );
	}
	catch( UnsupportedEncodingException e ) {
	    e.printStackTrace();
	}
    }

    /**
     * Remove the frame with the specified id from the file.  If there is no
     * frame with that id nothing will happen.
     *
     * @param id the id of the frame to remove
     */
    public void removeFrame( String id ) {
	frames.remove( id );
	updateSize();
    }

    /**
     * Updates the data for the frame specified by id.  If no frame exists for
     * the id specified, a new frame with that id is created.
     *
     * @param id the id of the frame to update
     * @param data the data for the frame
     */
    public void updateFrameData( String id, byte[] data ) {
	if( frames.containsKey( id ) ) {
	    ((ID3v2Frame)frames.get( id )).setFrameData( data );
	}
	else {
	    ID3v2Frame frame = new ID3v2Frame( id, data );
	    frames.put( id, frame );
	}
	
	updateSize();
    }

    /**
     * Returns the textual information contained in the frame specified by the
     * id.  Not every type of frame has textual information.  If an id is 
     * specified that will not work, the empty string is returned.
     *
     * @param id the id of the frame to get text from
     * @return the text information contained in the frame
     * @exception ID3v2FormatException if an error is encountered parsing data
     */
    public String getFrameDataString( String id ) throws ID3v2FormatException {
	String str = new String();

	if( frames.containsKey( id ) ) {
	    str = ((ID3v2Frame)frames.get( id )).getDataString();
	}

	return str;
    }

    /**
     * Returns the data found in the frame specified by the id.  If the frame
     * doesn't exist, then a zero length array is returned.
     *
     * @param id the id of the frame to get the data from
     * @return the data found in the frame
     */
    public byte[] getFrameData( String id ) {
	byte[] b = new byte[0];
	
	if( frames.containsKey( id ) ) {
	    b = ((ID3v2Frame)frames.get( id )).getFrameData();
	}

	return b;
    }

    /**
     * Updates the size field of the id3 header and footer (if it exists) 
     * from the current size of the id3v2 frames plus the extended header 
     * size (if it exists).
     *
     */
    private void updateSize() {
	int length = frames.getLength();

	if( head.getExtendedHeader() ){
	    length += ext_head.getSize();
	}

	head.setTagSize( length );

	if( head.getFooter() ) {
	    foot.setTagSize( length );
	}
    }

    /**
     * Returns true if an id3v2 tag exists in the file that was passed to the 
     * constructor and false otherwise
     *
     * @return true if an id3v2 tag exists in the file passed to the ctor
     */
    public boolean tagExists() {
	return exists;
    }

    /**
     * Returns the size of this id3v2 tag.  This includes the header, 
     * extended header, frames, padding, and footer.
     *
     * @return the size (in bytes) of the entire id3v2 tag
     */
    public int getSize() {
	int retval = head.getTagSize() + head.getHeaderSize();

	if( head.getFooter() ) {
	    retval += foot.getFooterSize();
	}

	return retval;
    }

    /**
     * Returns the current number of padding bytes in this id3v2 tag.
     *
     * @return the current number of padding bytes in this id3v2 tag
     */
    public int getPadding() {
	return padding;
    }

    /**
     * Set the amount of padding to use when writing this tag.  There cannot
     * be any padding if a footer exists.  Nothing will happen if this function
     * is called and a footer exists or if the number is negative.
     *
     * @param pad the amount of padding to use when writing this tag
     */
    public void setPadding( int pad ) {
	if( !head.getFooter() && (pad >= 0) ) {
	    padding = pad;
	}
    }

    /**
     * Return a string representation of this object.  This includes all data
     * contained in all parts of this tag.
     *
     * @return a string representation of this object
     */
    public String toString() {
	String str = head.toString();

	str += "\nPadding:\t\t\t" + getPadding() + " bytes";

	if( head.getExtendedHeader() ) {
	    str += "\n" + ext_head.toString();
	}

	str += "\n" + frames.toString();

	if( head.getFooter() ) {
	    str += foot.toString();
	}

	return str;
    }

} // ID3v2Tag