Package org.apache.commons.compress.harmony.unpack200

Class Segment

java.lang.Object
org.apache.commons.compress.harmony.unpack200.Segment
public class Segment extends Object
A Pack200 archive consists of one or more segments. Each segment is stand-alone, in the sense that every segment has the magic number header; thus, every segment is also a valid archive. However, it is possible to combine (non-GZipped) archives into a single large archive by concatenation alone. Thus, all the hard work in unpacking an archive falls to understanding a segment.

The first component of a segment is the header; this contains (amongst other things) the expected counts of constant pool entries, which in turn defines how many values need to be read from the stream. Because values are variable width (see Codec), it is not possible to calculate the start of the next segment, although one of the header values does hint at the size of the segment if non-zero, which can be used for buffering purposes.

Note that this does not perform any buffering of the input stream; each value will be read on a byte-by-byte basis. It does not perform GZip decompression automatically; both of these are expected to be done by the caller if the stream has the magic header for GZip streams (GZIPInputStream.GZIP_MAGIC). In any case, if GZip decompression is being performed the input stream will be buffered at a higher level, and thus this can read on a byte-oriented basis.

Format: 

   pack200_archive:
      (pack200_segment)+

   pack200_segment:
      segment_header
      *band_headers :BYTE1
      cp_bands
      attr_definition_bands
      ic_bands
      class_bands
      bc_bands
      file_bands

  • Field Details

  • Constructor Details

  • Method Details

    • getAttrDefinitionBands

      protected AttrDefinitionBands getAttrDefinitionBands()

    • getClassBands

      protected ClassBands getClassBands()

    • getConstantPool

      public SegmentConstantPool getConstantPool()
      Gets the constant pool.
      Returns:
      the constant pool.

    • getCpBands

      protected CpBands getCpBands()
      Gets the constant pool bands.
      Returns:
      the constant pool bands.

    • getIcBands

      protected IcBands getIcBands()
      Gets the inner class bands.
      Returns:
      the inner class bands.

    • getSegmentHeader

      public SegmentHeader getSegmentHeader()
      Gets the segment header.
      Returns:
      the segment header.

    • log

      public void log(int messageLevel, String message)
      Logs a message.
      Parameters:
      messageLevel - the message level.
      message - the message.

    • overrideDeflateHint

      public void overrideDeflateHint(boolean deflateHint)
      Overrides the archive's deflate hint with the given boolean
      Parameters:
      deflateHint - the deflate hint to use

    • setLogLevel

      public void setLogLevel(int logLevel)
      Sets the log level.
      Parameters:
      logLevel - the log level.

    • setLogStream

      public void setLogStream(OutputStream logStream)
      Sets the log output stream.
      Parameters:
      logStream - log output stream.

    • setPreRead

      public void setPreRead(boolean value)
      Sets whether unpacking buffers its input.
      Parameters:
      value - whether unpacking buffers its input.

    • unpack

      public void unpack(InputStream inputStream, JarOutputStream out) throws IOException, Pack200Exception
      Unpacks a packed stream (either .pack. or .pack.gz) into a corresponding JarOuputStream.
      Parameters:
      inputStream - a packed input stream, preferably a BoundedInputStream.
      out - output stream.
      Throws:
      Pack200Exception - if there is a problem unpacking
      IOException - if there is a problem with I/O during unpacking

    • writeJar

      public void writeJar(JarOutputStream out) throws IOException
      Writes the segment to an output stream. The output stream should be pre-buffered for efficiency. Also takes the same input stream for reading, since the file bits may not be loaded and thus just copied from one stream to another. Doesn't close the output stream when finished, in case there are more entries (for example further segments) to be written.
      Parameters:
      out - the JarOutputStream to write data to
      Throws:
      IOException - if an error occurs while reading or writing to the streams