| java.lang.Object
 sun.misc.CharacterDecoder
All known Subclasses: sun.misc.BASE64Decoder,
| CharacterDecoder | | abstract public class CharacterDecoder (Code) | | 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.
version:
05/03/00, 1.17
author:
Chuck McManis
See Also: CEFormatException
See Also: CharacterEncoder
See Also: UCDecoder
See Also: UUDecoder
See Also: BASE64Decoder |
| Method Summary | |
| abstract protected int | bytesPerAtom()
| | abstract protected int | bytesPerLine()
| | protected void | decodeAtom(InputStream aStream, OutputStream bStream, int l)
This method does an actual decode. | | public void | decodeBuffer(InputStream aStream, OutputStream bStream)
Decode the text from the InputStream and write the decoded
octets to the OutputStream. | | public byte | decodeBuffer(String inputString)
Alternate decode interface that takes a String containing the encoded
buffer and returns a byte array containing the data. | | public byte | decodeBuffer(InputStream in)
Decode the contents of the inputstream into a buffer. | | protected void | decodeBufferPrefix(InputStream aStream, OutputStream bStream)
decode the beginning of the buffer, by default this is a NOP. | | protected void | decodeBufferSuffix(InputStream aStream, OutputStream bStream)
decode the buffer suffix, again by default it is a NOP. | | protected int | decodeLinePrefix(InputStream aStream, OutputStream bStream)
This method should return, if it knows, the number of bytes
that will be decoded. | | protected void | decodeLineSuffix(InputStream aStream, OutputStream bStream)
This method post processes the line, if there are error detection
or correction codes in a line, they are generally processed by
this method. | | protected int | readFully(InputStream in, byte buffer, int offset, int len)
This method works around the bizarre semantics of BufferedInputStream's
read method. |
| bytesPerAtom | | abstract protected int bytesPerAtom()(Code) | | Return the number of bytes per atom of decoding
|
| bytesPerLine | | abstract protected int bytesPerLine()(Code) | | Return the maximum number of bytes that can be encoded per line
|
| decodeAtom | | protected void decodeAtom(InputStream aStream, OutputStream bStream, int l) throws IOException(Code) | | 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().
|
| decodeBuffer | | public void decodeBuffer(InputStream aStream, OutputStream bStream) throws IOException(Code) | | Decode the text from the InputStream and write the decoded
octets to the OutputStream. This method runs until the stream
is exhausted.
exception:
CEFormatException - An error has occured while decoding
exception:
CEStreamExhausted - The input stream is unexpectedly out of data |
| decodeBuffer | | public byte decodeBuffer(String inputString) throws IOException(Code) | | Alternate decode interface that takes a String containing the encoded
buffer and returns a byte array containing the data.
exception:
CEFormatException - An error has occured while decoding |
| decodeLinePrefix | | protected int decodeLinePrefix(InputStream aStream, OutputStream bStream) throws IOException(Code) | | 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.
|
| decodeLineSuffix | | protected void decodeLineSuffix(InputStream aStream, OutputStream bStream) throws IOException(Code) | | 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.
|
| readFully | | protected int readFully(InputStream in, byte buffer, int offset, int len) throws java.io.IOException(Code) | | This method works around the bizarre semantics of BufferedInputStream's
read method.
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