org.spaceroots.jarmor
Class ASCII85Decoder

java.lang.Object
  java.io.InputStream
      java.io.FilterInputStream
          org.spaceroots.jarmor.AbstractDecoder
              org.spaceroots.jarmor.ASCII85Decoder

public class ASCII85Decoder

extends org.spaceroots.jarmor.AbstractDecoder

This class decodes a text stream containing into a binary stream.

The ASCII85encoding is suitable when binary data needs to be transmitted or stored as text. It has been defined by Adobe for the PostScript and PDF formats (see PDF Reference, section 3.3 Details of Filtered Streams).

The encoded stream is about 25% larger than the corresponding binary stream (32 binary bits are converted into 40 encoded bits, and there may be start/end of line markers).

Author:

Luc Maisonobe

See Also:

ASCII85Encoder

Field Summary

protected byte[]	encoded Encoded bytes buffer.
protected boolean	endReached End indicator.
protected int	nEncoded Number of bytes already in the encoded array.

Fields inherited from class java.io.FilterInputStream

in

Constructor Summary

ASCII85Decoder(InputStream in)
Create a decoder wrapping a source of encoded data.

Method Summary

int	available() Get the number of bytes that can be read from this input stream without blocking.
void	close() Close the stream.
protected int	filterBytes() Filter some bytes from the underlying stream.
boolean	markSupported() Check if the FilterInputStream.mark(int) and FilterInputStream.reset() methods are supported.
protected void	putFilteredByte(int b) Put a filtered byte in the buffer.
int	read() Reads the next byte of data from this input stream.
int	read(byte[] b, int off, int len) Reads up to len bytes of data from this input stream into an array of bytes.
protected int	readEncodedBytes() Read new encoded bytes.
long	skip(long n) Skips over and discards n bytes of data from the input stream.

Methods inherited from class java.io.FilterInputStream

mark, read, reset

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

encoded

protected byte[] encoded

Encoded bytes buffer.

nEncoded

protected int nEncoded

Number of bytes already in the encoded array.

endReached

protected boolean endReached

End indicator.

Constructor Detail

ASCII85Decoder

public ASCII85Decoder(InputStream in)

Create a decoder wrapping a source of encoded data.

Parameters:

in - source of encoded data to decode

Method Detail

filterBytes

protected int filterBytes()
                   throws IOException

Filter some bytes from the underlying stream.

Returns:

number of bytes inserted in the filtered bytes buffer or -1

Throws:

IOException - if the underlying stream throws one or if a non-ASCII85 character is encountered

See Also:

AbstractDecoder.putFilteredByte(int)

available

public int available()
              throws IOException

Get the number of bytes that can be read from this input stream without blocking.

Returns:

number of bytes that can be read from this input stream without blocking

Throws:

IOException - if the underlying stream throws one

read

public int read()
         throws IOException

Reads the next byte of data from this input stream.

Returns:

the next byte of data, or -1 if the end of the stream is reached.

Throws:

IOException - if the underlying stream throws one

read

public int read(byte[] b,
                int off,
                int len)
         throws IOException

Reads up to len bytes of data from this input stream into an array of bytes.

Parameters:

b - the buffer into which the data is read.

off - the start offset of the data.

len - the maximum number of bytes read.

Returns:

the total number of bytes read into the buffer, or -1 if there is no more data because the end of the stream has been reached

Throws:

IOException - if the underlying stream throws one

skip

public long skip(long n)
          throws IOException

Skips over and discards n bytes of data from the input stream.

Parameters:

n - the number of bytes to be skipped

Returns:

the actual number of bytes skipped

Throws:

IOException - if the underlying stream throws one

close

public void close()
           throws IOException

Close the stream.

Throws:

IOException - if the underlying stream throws one

markSupported

public boolean markSupported()

Check if the FilterInputStream.mark(int) and FilterInputStream.reset() methods are supported.

Returns:

always false

readEncodedBytes

protected int readEncodedBytes()
                        throws IOException

Read new encoded bytes.

Returns:

number of bytes read or -1 if the underlying stream has no bytes left

Throws:

IOException - if the underlying stream throws one

putFilteredByte

protected void putFilteredByte(int b)

Put a filtered byte in the buffer.

The filtered bytes buffer will be expanded if it already contains too many pending bytes.

Parameters:

b - byte to put in the filtered buffer