org.apache.batik.util.svg
Class CharacterDecoder

java.lang.Object
  |
  +--org.apache.batik.util.svg.CharacterDecoder
Direct Known Subclasses:
Base64Decoder

public abstract class CharacterDecoder
extends java.lang.Object

This class defines the decoding half of character encoders. A character decoder is an algorithim for transforming 8 bit binary data that has been encoded into text by a character encoder, back into original binary form. The character encoders, in general, have been structured around a central theme that binary data can be encoded into text that has the form:

	[Buffer Prefix]
	[Line Prefix][encoded data atoms][Line Suffix]
	[Buffer Suffix]
 
Of course in the simplest encoding schemes, the buffer has no distinct prefix of suffix, however all have some fixed relationship between the text in an 'atom' and the binary data itself. In the CharacterEncoder and CharacterDecoder classes, one complete chunk of data is referred to as a buffer. Encoded buffers are all text, and decoded buffers (sometimes just referred to as buffers) are binary octets. To create a custom decoder, you must, at a minimum, overide three abstract methods in this class.
bytesPerAtom which tells the decoder how many bytes to expect from decodeAtom
decodeAtom which decodes the bytes sent to it as text.
bytesPerLine which tells the encoder the maximum number of bytes per line.
In general, the character decoders return error in the form of an IOException. The syntax of the detail string is
	DecoderClassName: Error message.
 
Several useful decoders have already been written and are referenced in the See Also list below.

See Also:
CharacterEncoder, Base64Decoder

Constructor Summary
CharacterDecoder()
           
 
Method Summary
 byte[] decodeBuffer(java.io.InputStream in)
          Decode the contents of the inputstream into a buffer.
 void decodeBuffer(java.io.InputStream aStream, java.io.OutputStream bStream)
          Decode the text from the InputStream and write the decoded octets to the OutputStream.
 byte[] decodeBuffer(java.lang.String inputString)
          Alternate decode interface that takes a String containing the encoded buffer and returns a byte array containing the data.
 
Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait
 

Constructor Detail

CharacterDecoder

public CharacterDecoder()
Method Detail

decodeBuffer

public void decodeBuffer(java.io.InputStream aStream,
                         java.io.OutputStream bStream)
                  throws java.io.IOException
Decode the text from the InputStream and write the decoded octets to the OutputStream. This method runs until the stream is exhausted.
Throws:
java.lang.RuntimeException - An error has occured while decoding
java.io.EOFException - The input stream is unexpectedly out of data

decodeBuffer

public byte[] decodeBuffer(java.lang.String inputString)
                    throws java.io.IOException
Alternate decode interface that takes a String containing the encoded buffer and returns a byte array containing the data.
Throws:
java.io.IOException - An error has occured while decoding

decodeBuffer

public byte[] decodeBuffer(java.io.InputStream in)
                    throws java.io.IOException
Decode the contents of the inputstream into a buffer.


Copyright © 2000 Apache Software Foundation. All Rights Reserved.