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Class sun.server.util.CharacterDecoder 

java.lang.Object
   |
   +----sun.server.util.CharacterDecoder
public abstract class CharacterDecoder
extends 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 a CEFormatException. 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:
CEFormatException, CharacterEncoder, UCDecoder, UUDecoder, BASE64Decoder

Constructor Index

o CharacterDecoder()

Method Index

o bytesPerAtom()
Return the number of bytes per atom of decoding
o bytesPerLine()
Return the maximum number of bytes that can be encoded per line
o decodeAtom(InputStream, OutputStream, int)
This method does an actual decode.
o decodeBuffer(InputStream)
Decode the contents of the inputstream into a buffer.
o decodeBuffer(InputStream, OutputStream)
Decode the text from the InputStream and write the decoded octets to the OutputStream.
o decodeBuffer(String)
Alternate decode interface that takes a String containing the encoded buffer and returns a byte array containing the data.
o decodeBufferPrefix(InputStream, OutputStream)
decode the beginning of the buffer, by default this is a NOP.
o decodeBufferSuffix(InputStream, OutputStream)
decode the buffer suffix, again by default it is a NOP.
o decodeLinePrefix(InputStream, OutputStream)
This method should return, if it knows, the number of bytes that will be decoded.
o decodeLineSuffix(InputStream, OutputStream)
This method post processes the line, if there are error detection or correction codes in a line, they are generally processed by this method.
o readFully(InputStream, byte[], int, int)
This method works around the bizarre semantics of BufferedInputStream's read method.

Constructors

o CharacterDecoder 
 public CharacterDecoder()

Methods

o bytesPerAtom 
 protected abstract int bytesPerAtom()
Return the number of bytes per atom of decoding

o bytesPerLine 
 protected abstract int bytesPerLine()
Return the maximum number of bytes that can be encoded per line

o decodeBufferPrefix 
 protected void decodeBufferPrefix(InputStream aStream,
                                   OutputStream bStream) throws IOException
decode the beginning of the buffer, by default this is a NOP.

o decodeBufferSuffix 
 protected void decodeBufferSuffix(InputStream aStream,
                                   OutputStream bStream) throws IOException
decode the buffer suffix, again by default it is a NOP.

o decodeLinePrefix 
 protected int decodeLinePrefix(InputStream aStream,
                                OutputStream bStream) throws IOException
This method should return, if it knows, the number of bytes that will be decoded. Many formats such as uuencoding provide this information. By default we return the maximum bytes that could have been encoded on the line.

o decodeLineSuffix 
 protected void decodeLineSuffix(InputStream aStream,
                                 OutputStream bStream) throws IOException
This method post processes the line, if there are error detection or correction codes in a line, they are generally processed by this method. The simplest version of this method looks for the (newline) character.

o decodeAtom 
 protected void decodeAtom(InputStream aStream,
                           OutputStream bStream,
                           int l) throws IOException
This method does an actual decode. It takes the decoded bytes and writes them to the OuputStream. The integer l tells the method how many bytes are required. This is always <= bytesPerAtom().

o readFully 
 protected int readFully(InputStream in,
                         byte buffer[],
                         int offset,
                         int len) throws IOException
This method works around the bizarre semantics of BufferedInputStream's read method.

o decodeBuffer 
 public void decodeBuffer(InputStream aStream,
                          OutputStream bStream) throws IOException
Decode the text from the InputStream and write the decoded octets to the OutputStream. This method runs until the stream is exhausted.

Throws: CEFormatException
An error has occured while decoding
Throws: CEStreamExhausted
The input stream is unexpectedly out of data
o decodeBuffer 
 public byte[] decodeBuffer(String inputString) throws IOException
Alternate decode interface that takes a String containing the encoded buffer and returns a byte array containing the data.

Throws: CEFormatException
An error has occured while decoding
o decodeBuffer 
 public byte[] decodeBuffer(InputStream in) throws IOException
Decode the contents of the inputstream into a buffer. 

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