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java.lang.Object | +--com.ibm.misc.CharacterDecoder
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.
DecoderClassName: Error message.Several useful decoders have already been written and are referenced in the See Also list below.
CEFormatException
,
CharacterEncoder
,
BASE64Decoder
Constructor Summary | |
CharacterDecoder()
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Method Summary | |
protected abstract int |
bytesPerAtom()
Return the number of bytes per atom of decoding |
protected abstract int |
bytesPerLine()
Return the maximum number of bytes that can be encoded per line |
protected void |
decodeAtom(InputStream aStream,
OutputStream bStream,
int l)
This method does an actual decode. |
byte[] |
decodeBuffer(InputStream in)
Decode the contents of the inputstream into a buffer. |
void |
decodeBuffer(InputStream aStream,
OutputStream bStream)
Decode the text from the InputStream and write the decoded octets to the OutputStream. |
byte[] |
decodeBuffer(String inputString)
Alternate decode interface that takes a String containing the encoded buffer and returns a byte array containing the data. |
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. |
Methods inherited from class java.lang.Object |
clone,
equals,
finalize,
getClass,
hashCode,
notify,
notifyAll,
toString,
wait,
wait,
wait |
Constructor Detail |
public CharacterDecoder()
Method Detail |
protected abstract int bytesPerAtom()
protected abstract int bytesPerLine()
protected void decodeBufferPrefix(InputStream aStream, OutputStream bStream) throws IOException
protected void decodeBufferSuffix(InputStream aStream, OutputStream bStream) throws IOException
protected int decodeLinePrefix(InputStream aStream, OutputStream bStream) throws IOException
protected void decodeLineSuffix(InputStream aStream, OutputStream bStream) throws IOException
protected void decodeAtom(InputStream aStream, OutputStream bStream, int l) throws IOException
protected int readFully(InputStream in, byte[] buffer, int offset, int len) throws IOException
public void decodeBuffer(InputStream aStream, OutputStream bStream) throws IOException
public byte[] decodeBuffer(String inputString) throws IOException
public byte[] decodeBuffer(InputStream in) throws IOException
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