Module java.base
Package java.util.zip

Class Inflater

java.lang.Object
java.util.zip.Inflater
public class Inflater extends Object
This class provides support for general purpose decompression using the popular ZLIB compression library. The ZLIB compression library was initially developed as part of the PNG graphics standard and is not protected by patents. It is fully described in the specifications at the java.util.zip package description.

This class inflates sequences of ZLIB compressed bytes. The input byte sequence is provided in either byte array or byte buffer, via one of the setInput() methods. The output byte sequence is written to the output byte array or byte buffer passed to the deflate() methods.

The following code fragment demonstrates a trivial compression and decompression of a string using Deflater and Inflater. 

 try {
     // Encode a String into bytes
     String inputString = "blahblahblah€€";
     byte[] input = inputString.getBytes("UTF-8");

     // Compress the bytes
     byte[] output = new byte[100];
     Deflater compresser = new Deflater();
     compresser.setInput(input);
     compresser.finish();
     int compressedDataLength = compresser.deflate(output);

     // Decompress the bytes
     Inflater decompresser = new Inflater();
     decompresser.setInput(output, 0, compressedDataLength);
     byte[] result = new byte[100];
     int resultLength = decompresser.inflate(result);
     decompresser.end();

     // Decode the bytes into a String
     String outputString = new String(result, 0, resultLength, "UTF-8");
 } catch (java.io.UnsupportedEncodingException ex) {
     // handle
 } catch (java.util.zip.DataFormatException ex) {
     // handle
 }
API Note:
To release resources used by this Inflater, the end() method should be called explicitly. Subclasses are responsible for the cleanup of resources acquired by the subclass. Subclasses that override Object.finalize() in order to perform cleanup should be modified to use alternative cleanup mechanisms such as Cleaner and remove the overriding finalize method.
Since:
1.1
See Also:
Deflater

  • Constructor Summary

    Constructors
    Constructor
    Description
    Inflater()
    Creates a new decompressor.
    Inflater​(boolean nowrap)
    Creates a new decompressor.

  • Method Summary

    Modifier and Type
    Method
    Description
    void
    end()
    Closes the decompressor and discards any unprocessed input.
    boolean
    finished()
    Returns true if the end of the compressed data stream has been reached.
    int
    getAdler()
    Returns the ADLER-32 value of the uncompressed data.
    long
    getBytesRead()
    Returns the total number of compressed bytes input so far.
    long
    getBytesWritten()
    Returns the total number of uncompressed bytes output so far.
    int
    getRemaining()
    Returns the total number of bytes remaining in the input buffer.
    int
    getTotalIn()
    Returns the total number of compressed bytes input so far.
    int
    getTotalOut()
    Returns the total number of uncompressed bytes output so far.
    int
    inflate​(byte[] output)
    Uncompresses bytes into specified buffer.
    int
    inflate​(byte[] output, int off, int len)
    Uncompresses bytes into specified buffer.
    int
    inflate​(ByteBuffer output)
    Uncompresses bytes into specified buffer.
    boolean
    needsDictionary()
    Returns true if a preset dictionary is needed for decompression.
    boolean
    needsInput()
    Returns true if no data remains in the input buffer.
    void
    reset()
    Resets inflater so that a new set of input data can be processed.
    void
    setDictionary​(byte[] dictionary)
    Sets the preset dictionary to the given array of bytes.
    void
    setDictionary​(byte[] dictionary, int off, int len)
    Sets the preset dictionary to the given array of bytes.
    void
    setDictionary​(ByteBuffer dictionary)
    Sets the preset dictionary to the bytes in the given buffer.
    void
    setInput​(byte[] input)
    Sets input data for decompression.
    void
    setInput​(byte[] input, int off, int len)
    Sets input data for decompression.
    void
    setInput​(ByteBuffer input)
    Sets input data for decompression.

    Methods declared in class java.lang.Object

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

  • Constructor Details

    • Inflater

      public Inflater​(boolean nowrap)
      Creates a new decompressor. If the parameter 'nowrap' is true then the ZLIB header and checksum fields will not be used. This provides compatibility with the compression format used by both GZIP and PKZIP.

      Note: When using the 'nowrap' option it is also necessary to provide an extra "dummy" byte as input. This is required by the ZLIB native library in order to support certain optimizations.

      Parameters:
      nowrap - if true then support GZIP compatible compression

    • Inflater

      public Inflater()
      Creates a new decompressor.

  • Method Details

    • setInput

      public void setInput​(byte[] input, int off, int len)
      Sets input data for decompression.

      One of the setInput() methods should be called whenever needsInput() returns true indicating that more input data is required.

      Parameters:
      input - the input data bytes
      off - the start offset of the input data
      len - the length of the input data
      See Also:
      needsInput()

    • setInput

      public void setInput​(byte[] input)
      Sets input data for decompression.

      One of the setInput() methods should be called whenever needsInput() returns true indicating that more input data is required.

      Parameters:
      input - the input data bytes
      See Also:
      needsInput()

    • setInput

      public void setInput​(ByteBuffer input)
      Sets input data for decompression.

      One of the setInput() methods should be called whenever needsInput() returns true indicating that more input data is required.

      The given buffer's position will be advanced as inflate operations are performed, up to the buffer's limit. The input buffer may be modified (refilled) between inflate operations; doing so is equivalent to creating a new buffer and setting it with this method.

      Modifying the input buffer's contents, position, or limit concurrently with an inflate operation will result in undefined behavior, which may include incorrect operation results or operation failure.

      Parameters:
      input - the input data bytes
      Since:
      11
      See Also:
      needsInput()

    • setDictionary

      public void setDictionary​(byte[] dictionary, int off, int len)
      Sets the preset dictionary to the given array of bytes. Should be called when inflate() returns 0 and needsDictionary() returns true indicating that a preset dictionary is required. The method getAdler() can be used to get the Adler-32 value of the dictionary needed.
      Parameters:
      dictionary - the dictionary data bytes
      off - the start offset of the data
      len - the length of the data
      See Also:
      needsDictionary(), getAdler()

    • setDictionary

      public void setDictionary​(byte[] dictionary)
      Sets the preset dictionary to the given array of bytes. Should be called when inflate() returns 0 and needsDictionary() returns true indicating that a preset dictionary is required. The method getAdler() can be used to get the Adler-32 value of the dictionary needed.
      Parameters:
      dictionary - the dictionary data bytes
      See Also:
      needsDictionary(), getAdler()

    • setDictionary

      public void setDictionary​(ByteBuffer dictionary)
      Sets the preset dictionary to the bytes in the given buffer. Should be called when inflate() returns 0 and needsDictionary() returns true indicating that a preset dictionary is required. The method getAdler() can be used to get the Adler-32 value of the dictionary needed.

      The bytes in given byte buffer will be fully consumed by this method. On return, its position will equal its limit.

      Parameters:
      dictionary - the dictionary data bytes
      Since:
      11
      See Also:
      needsDictionary(), getAdler()

    • getRemaining

      public int getRemaining()
      Returns the total number of bytes remaining in the input buffer. This can be used to find out what bytes still remain in the input buffer after decompression has finished.
      Returns:
      the total number of bytes remaining in the input buffer

    • needsInput

      public boolean needsInput()
      Returns true if no data remains in the input buffer. This can be used to determine if one of the setInput() methods should be called in order to provide more input.
      Returns:
      true if no data remains in the input buffer

    • needsDictionary

      public boolean needsDictionary()
      Returns true if a preset dictionary is needed for decompression.
      Returns:
      true if a preset dictionary is needed for decompression
      See Also:
      setDictionary(byte[], int, int)

    • finished

      public boolean finished()
      Returns true if the end of the compressed data stream has been reached.
      Returns:
      true if the end of the compressed data stream has been reached

    • inflate

      public int inflate​(byte[] output, int off, int len) throws DataFormatException
      Uncompresses bytes into specified buffer. Returns actual number of bytes uncompressed. A return value of 0 indicates that needsInput() or needsDictionary() should be called in order to determine if more input data or a preset dictionary is required. In the latter case, getAdler() can be used to get the Adler-32 value of the dictionary required.

      If the setInput(ByteBuffer) method was called to provide a buffer for input, the input buffer's position will be advanced by the number of bytes consumed by this operation, even in the event that a DataFormatException is thrown.

      The remaining byte count will be reduced by the number of consumed input bytes. If the setInput(ByteBuffer) method was called to provide a buffer for input, the input buffer's position will be advanced the number of consumed bytes.

      These byte totals, as well as the total bytes read and the total bytes written values, will be updated even in the event that a DataFormatException is thrown to reflect the amount of data consumed and produced before the exception occurred.

      Parameters:
      output - the buffer for the uncompressed data
      off - the start offset of the data
      len - the maximum number of uncompressed bytes
      Returns:
      the actual number of uncompressed bytes
      Throws:
      DataFormatException - if the compressed data format is invalid
      See Also:
      needsInput(), needsDictionary()

    • inflate

      public int inflate​(byte[] output) throws DataFormatException
      Uncompresses bytes into specified buffer. Returns actual number of bytes uncompressed. A return value of 0 indicates that needsInput() or needsDictionary() should be called in order to determine if more input data or a preset dictionary is required. In the latter case, getAdler() can be used to get the Adler-32 value of the dictionary required.

      The remaining byte count will be reduced by the number of consumed input bytes. If the setInput(ByteBuffer) method was called to provide a buffer for input, the input buffer's position will be advanced the number of consumed bytes.

      These byte totals, as well as the total bytes read and the total bytes written values, will be updated even in the event that a DataFormatException is thrown to reflect the amount of data consumed and produced before the exception occurred.

      Parameters:
      output - the buffer for the uncompressed data
      Returns:
      the actual number of uncompressed bytes
      Throws:
      DataFormatException - if the compressed data format is invalid
      See Also:
      needsInput(), needsDictionary()

    • inflate

      public int inflate​(ByteBuffer output) throws DataFormatException
      Uncompresses bytes into specified buffer. Returns actual number of bytes uncompressed. A return value of 0 indicates that needsInput() or needsDictionary() should be called in order to determine if more input data or a preset dictionary is required. In the latter case, getAdler() can be used to get the Adler-32 value of the dictionary required.

      On success, the position of the given output byte buffer will be advanced by as many bytes as were produced by the operation, which is equal to the number returned by this method. Note that the position of the output buffer will be advanced even in the event that a DataFormatException is thrown.

      The remaining byte count will be reduced by the number of consumed input bytes. If the setInput(ByteBuffer) method was called to provide a buffer for input, the input buffer's position will be advanced the number of consumed bytes.

      These byte totals, as well as the total bytes read and the total bytes written values, will be updated even in the event that a DataFormatException is thrown to reflect the amount of data consumed and produced before the exception occurred.

      Parameters:
      output - the buffer for the uncompressed data
      Returns:
      the actual number of uncompressed bytes
      Throws:
      DataFormatException - if the compressed data format is invalid
      ReadOnlyBufferException - if the given output buffer is read-only
      Since:
      11
      See Also:
      needsInput(), needsDictionary()

    • getAdler

      public int getAdler()
      Returns the ADLER-32 value of the uncompressed data.
      Returns:
      the ADLER-32 value of the uncompressed data

    • getTotalIn

      public int getTotalIn()
      Returns the total number of compressed bytes input so far.

      Since the number of bytes may be greater than Integer.MAX_VALUE, the getBytesRead() method is now the preferred means of obtaining this information.

      Returns:
      the total number of compressed bytes input so far

    • getBytesRead

      public long getBytesRead()
      Returns the total number of compressed bytes input so far.
      Returns:
      the total (non-negative) number of compressed bytes input so far
      Since:
      1.5

    • getTotalOut

      public int getTotalOut()
      Returns the total number of uncompressed bytes output so far.

      Since the number of bytes may be greater than Integer.MAX_VALUE, the getBytesWritten() method is now the preferred means of obtaining this information.

      Returns:
      the total number of uncompressed bytes output so far

    • getBytesWritten

      public long getBytesWritten()
      Returns the total number of uncompressed bytes output so far.
      Returns:
      the total (non-negative) number of uncompressed bytes output so far
      Since:
      1.5

    • reset

      public void reset()
      Resets inflater so that a new set of input data can be processed.

    • end

      public void end()
      Closes the decompressor and discards any unprocessed input. This method should be called when the decompressor is no longer being used. Once this method is called, the behavior of the Inflater object is undefined.