Package net.sf.jazzlib

Class Deflater

  • public class Deflater
extends java.lang.Object
    This is the Deflater class. The deflater class compresses input with the deflate algorithm described in RFC 1951. It has several compression levels and three different strategies described below. This class is not thread safe. This is inherent in the API, due to the split of deflate and setInput.

    • Constructor Summary

      Constructors 
      Constructor Description
      Deflater()
      Creates a new deflater with default compression level.
      Deflater​(int lvl)
      Creates a new deflater with given compression level.
      Deflater​(int lvl, boolean nowrap)
      Creates a new deflater with given compression level.

    • Method Summary

      All Methods Instance Methods Concrete Methods Deprecated Methods 
      Modifier and Type Method Description
      int deflate​(byte[] output)
      Deflates the current input block to the given array.
      int deflate​(byte[] output, int offset, int length)
      Deflates the current input block to the given array.
      void end()
      Deprecated.
      Just clear all references to deflater instead.
      protected void finalize()
      Finalizes this object.
      void finish()
      Finishes the deflater with the current input block.
      boolean finished()
      Returns true iff the stream was finished and no more output bytes are available.
      (package private) void flush()
      Flushes the current input block.
      int getAdler()
      Gets the current adler checksum of the data that was processed so far.
      int getTotalIn()
      Gets the number of input bytes processed so far.
      int getTotalOut()
      Gets the number of output bytes so far.
      boolean needsInput()
      Returns true, if the input buffer is empty.
      void reset()
      Resets the deflater.
      void setDictionary​(byte[] dict)
      Sets the dictionary which should be used in the deflate process.
      void setDictionary​(byte[] dict, int offset, int length)
      Sets the dictionary which should be used in the deflate process.
      void setInput​(byte[] input)
      Sets the data which should be compressed next.
      void setInput​(byte[] input, int off, int len)
      Sets the data which should be compressed next.
      void setLevel​(int lvl)
      Sets the compression level.
      void setStrategy​(int stgy)
      Sets the compression strategy.

      • Methods inherited from class java.lang.Object

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

    • Field Detail

      • BEST_COMPRESSION

        public static final int BEST_COMPRESSION
        The best and slowest compression level. This tries to find very long and distant string repetitions.
        See Also:
        Constant Field Values

      • BEST_SPEED

        public static final int BEST_SPEED
        The worst but fastest compression level.
        See Also:
        Constant Field Values

      • DEFAULT_COMPRESSION

        public static final int DEFAULT_COMPRESSION
        The default compression level.
        See Also:
        Constant Field Values

      • NO_COMPRESSION

        public static final int NO_COMPRESSION
        This level won't compress at all but output uncompressed blocks.
        See Also:
        Constant Field Values

      • DEFAULT_STRATEGY

        public static final int DEFAULT_STRATEGY
        The default strategy.
        See Also:
        Constant Field Values

      • FILTERED

        public static final int FILTERED
        This strategy will only allow longer string repetitions. It is useful for random data with a small character set.
        See Also:
        Constant Field Values

      • HUFFMAN_ONLY

        public static final int HUFFMAN_ONLY
        This strategy will not look for string repetitions at all. It only encodes with Huffman trees (which means, that more common characters get a smaller encoding.
        See Also:
        Constant Field Values

      • DEFLATED

        public static final int DEFLATED
        The compression method. This is the only method supported so far. There is no need to use this constant at all.
        See Also:
        Constant Field Values

      • level

        private int level
        Compression level.

      • noHeader

        private final boolean noHeader
        should we include a header.

      • state

        private int state
        The current state.

      • totalOut

        private int totalOut
        The total bytes of output written.

    • Constructor Detail

      • Deflater

        public Deflater()
        Creates a new deflater with default compression level.

      • Deflater

        public Deflater​(int lvl)
        Creates a new deflater with given compression level.
        Parameters:
        lvl - the compression level, a value between NO_COMPRESSION and BEST_COMPRESSION, or DEFAULT_COMPRESSION.
        Throws:
        java.lang.IllegalArgumentException - if lvl is out of range.

      • Deflater

        public Deflater​(int lvl,
                boolean nowrap)
        Creates a new deflater with given compression level.
        Parameters:
        lvl - the compression level, a value between NO_COMPRESSION and BEST_COMPRESSION.
        nowrap - true, iff we should suppress the deflate header at the beginning and the adler checksum at the end of the output. This is useful for the GZIP format.
        Throws:
        java.lang.IllegalArgumentException - if lvl is out of range.

    • Method Detail

      • reset

        public void reset()
        Resets the deflater. The deflater acts afterwards as if it was just created with the same compression level and strategy as it had before.

      • end

        @Deprecated
public void end()
        Deprecated.
        Just clear all references to deflater instead.
        Frees all objects allocated by the compressor. There's no reason to call this, since you can just rely on garbage collection. Exists only for compatibility against Sun's JDK, where the compressor allocates native memory. If you call any method (even reset) afterwards the behaviour is undefined.

      • getAdler

        public int getAdler()
        Gets the current adler checksum of the data that was processed so far.

      • getTotalIn

        public int getTotalIn()
        Gets the number of input bytes processed so far.

      • getTotalOut

        public int getTotalOut()
        Gets the number of output bytes so far.

      • finalize

        protected void finalize()
        Finalizes this object.
        Overrides:
        finalize in class java.lang.Object

      • flush

        void flush()
        Flushes the current input block. Further calls to deflate() will produce enough output to inflate everything in the current input block. This is not part of Sun's JDK so I have made it package private. It is used by DeflaterOutputStream to implement flush().

      • finish

        public void finish()
        Finishes the deflater with the current input block. It is an error to give more input after this method was called. This method must be called to force all bytes to be flushed.

      • finished

        public boolean finished()
        Returns true iff the stream was finished and no more output bytes are available.

      • needsInput

        public boolean needsInput()
        Returns true, if the input buffer is empty. You should then call setInput().
        NOTE: This method can also return true when the stream was finished.

      • setInput

        public void setInput​(byte[] input)
        Sets the data which should be compressed next. This should be only called when needsInput indicates that more input is needed. If you call setInput when needsInput() returns false, the previous input that is still pending will be thrown away. The given byte array should not be changed, before needsInput() returns true again. This call is equivalent to setInput(input, 0, input.length).
        Parameters:
        input - the buffer containing the input data.
        Throws:
        java.lang.IllegalStateException - if the buffer was finished() or ended().

      • setInput

        public void setInput​(byte[] input,
                     int off,
                     int len)
        Sets the data which should be compressed next. This should be only called when needsInput indicates that more input is needed. The given byte array should not be changed, before needsInput() returns true again.
        Parameters:
        input - the buffer containing the input data.
        off - the start of the data.
        len - the length of the data.
        Throws:
        java.lang.IllegalStateException - if the buffer was finished() or ended() or if previous input is still pending.

      • setLevel

        public void setLevel​(int lvl)
        Sets the compression level. There is no guarantee of the exact position of the change, but if you call this when needsInput is true the change of compression level will occur somewhere near before the end of the so far given input.
        Parameters:
        lvl - the new compression level.

      • setStrategy

        public void setStrategy​(int stgy)
        Sets the compression strategy. Strategy is one of DEFAULT_STRATEGY, HUFFMAN_ONLY and FILTERED. For the exact position where the strategy is changed, the same as for setLevel() applies.
        Parameters:
        stgy - the new compression strategy.

      • deflate

        public int deflate​(byte[] output)
        Deflates the current input block to the given array. It returns the number of bytes compressed, or 0 if either needsInput() or finished() returns true or length is zero.
        Parameters:
        output - the buffer where to write the compressed data.

      • deflate

        public int deflate​(byte[] output,
                   int offset,
                   int length)
        Deflates the current input block to the given array. It returns the number of bytes compressed, or 0 if either needsInput() or finished() returns true or length is zero.
        Parameters:
        output - the buffer where to write the compressed data.
        offset - the offset into the output array.
        length - the maximum number of bytes that may be written.
        Throws:
        java.lang.IllegalStateException - if end() was called.
        java.lang.IndexOutOfBoundsException - if offset and/or length don't match the array length.

      • setDictionary

        public void setDictionary​(byte[] dict)
        Sets the dictionary which should be used in the deflate process. This call is equivalent to setDictionary(dict, 0, dict.length).
        Parameters:
        dict - the dictionary.
        Throws:
        java.lang.IllegalStateException - if setInput () or deflate () were already called or another dictionary was already set.

      • setDictionary

        public void setDictionary​(byte[] dict,
                          int offset,
                          int length)
        Sets the dictionary which should be used in the deflate process. The dictionary should be a byte array containing strings that are likely to occur in the data which should be compressed. The dictionary is not stored in the compressed output, only a checksum. To decompress the output you need to supply the same dictionary again.
        Parameters:
        dict - the dictionary.
        offset - an offset into the dictionary.
        length - the length of the dictionary.
        Throws:
        java.lang.IllegalStateException - if setInput () or deflate () were already called or another dictionary was already set.