Package java.util.zip

Class Inflater

java.lang.Object
java.util.zip.Inflater
public class Inflater
extends Object
This class decompresses data that was compressed using the DEFLATE algorithm (see specification).

It is usually more convenient to use InflaterInputStream.

To decompress an in-memory byte[] to another in-memory byte[] manually: 

     byte[] compressedBytes = ...
     int decompressedByteCount = ... // From your format's metadata.
     Inflater inflater = new Inflater();
     inflater.setInput(compressedBytes, 0, compressedBytes.length);
     byte[] decompressedBytes = new byte[decompressedByteCount];
     if (inflater.inflate(decompressedBytes) != decompressedByteCount) {
         throw new AssertionError();
     }
     inflater.end();

In situations where you don't have all the input in one array (or have so much input that you want to feed it to the inflater in chunks), it's possible to call setInput(byte[]) repeatedly, but you're much better off using InflaterInputStream to handle all this for you.

If you don't know how big the decompressed data will be, you can call inflate(byte[]) repeatedly on a temporary buffer, copying the bytes to a ByteArrayOutputStream, but this is probably another sign you'd be better off using InflaterInputStream.

  • Constructor Summary

    Constructors
    Constructor Description
    Inflater()
    This constructor creates an inflater that expects a header from the input stream.
    Inflater​(boolean noHeader)
    This constructor allows to create an inflater that expects no header from the input stream.

  • Method Summary

    Modifier and Type Method Description
    void end()
    Releases resources associated with this Inflater.
    protected void finalize()
    Invoked when the garbage collector has detected that this instance is no longer reachable.
    boolean finished()
    Indicates if the Inflater has inflated the entire deflated stream.
    int getAdler()
    Returns the Adler32 checksum of the bytes inflated so far, or the checksum of the preset dictionary if needsDictionary returns true.
    long getBytesRead()
    Returns the total number of bytes read by the Inflater.
    long getBytesWritten()
    Returns a the total number of bytes written by this Inflater.
    int getRemaining()
    Returns the number of bytes of current input remaining to be read by this inflater.
    int getTotalIn()
    Returns the total number of bytes of input read by this Inflater.
    int getTotalOut()
    Returns the total number of bytes written to the output buffer by this Inflater.
    int inflate​(byte[] buf)
    Inflates bytes from the current input and stores them in buf.
    int inflate​(byte[] buf, int offset, int byteCount)
    Inflates up to byteCount bytes from the current input and stores them in buf starting at offset.
    boolean needsDictionary()
    Returns true if the input bytes were compressed with a preset dictionary.
    boolean needsInput()
    Returns true if setInput(byte[]) must be called before inflation can continue.
    void reset()
    Resets this Inflater.
    void setDictionary​(byte[] dictionary)
    Sets the preset dictionary to be used for inflation to dictionary.
    void setDictionary​(byte[] dictionary, int offset, int byteCount)
    Sets the preset dictionary to be used for inflation to a subsequence of dictionary starting at offset and continuing for byteCount bytes.
    void setInput​(byte[] buf)
    Sets the current input to to be decompressed.
    void setInput​(byte[] buf, int offset, int byteCount)
    Sets the current input to to be decompressed.

    Methods inherited from class java.lang.Object

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

  • Constructor Details

    • Inflater

      public Inflater()
      This constructor creates an inflater that expects a header from the input stream. Use Inflater(boolean) if the input comes without a ZLIB header.

    • Inflater

      public Inflater​(boolean noHeader)
      This constructor allows to create an inflater that expects no header from the input stream.
      Parameters:
      noHeader - true indicates that no ZLIB header comes with the input.

  • Method Details

    • end

      public void end()
      Releases resources associated with this Inflater. Any unused input or output is discarded. This method should be called explicitly in order to free native resources as soon as possible. After end() is called, other methods will typically throw IllegalStateException.

    • finalize

      protected void finalize()
      Description copied from class: Object
      Invoked when the garbage collector has detected that this instance is no longer reachable. The default implementation does nothing, but this method can be overridden to free resources.

      Note that objects that override finalize are significantly more expensive than objects that don't. Finalizers may be run a long time after the object is no longer reachable, depending on memory pressure, so it's a bad idea to rely on them for cleanup. Note also that finalizers are run on a single VM-wide finalizer thread, so doing blocking work in a finalizer is a bad idea. A finalizer is usually only necessary for a class that has a native peer and needs to call a native method to destroy that peer. Even then, it's better to provide an explicit close method (and implement Closeable), and insist that callers manually dispose of instances. This works well for something like files, but less well for something like a BigInteger where typical calling code would have to deal with lots of temporaries. Unfortunately, code that creates lots of temporaries is the worst kind of code from the point of view of the single finalizer thread.

      If you must use finalizers, consider at least providing your own ReferenceQueue and having your own thread process that queue.

      Unlike constructors, finalizers are not automatically chained. You are responsible for calling super.finalize() yourself.

      Uncaught exceptions thrown by finalizers are ignored and do not terminate the finalizer thread. See Effective Java Item 7, "Avoid finalizers" for more.

      Overrides:
      finalize in class Object

    • finished

      public boolean finished()
      Indicates if the Inflater has inflated the entire deflated stream. If deflated bytes remain and needsInput() returns true this method will return false. This method should be called after all deflated input is supplied to the Inflater.
      Returns:
      true if all input has been inflated, false otherwise.

    • getAdler

      public int getAdler()
      Returns the Adler32 checksum of the bytes inflated so far, or the checksum of the preset dictionary if needsDictionary returns true.

    • getBytesRead

      public long getBytesRead()
      Returns the total number of bytes read by the Inflater. This method is the same as getTotalIn() except that it returns a long value instead of an integer.

    • getBytesWritten

      public long getBytesWritten()
      Returns a the total number of bytes written by this Inflater. This method is the same as getTotalOut except it returns a long value instead of an integer.

    • getRemaining

      public int getRemaining()
      Returns the number of bytes of current input remaining to be read by this inflater.

    • getTotalIn

      public int getTotalIn()
      Returns the total number of bytes of input read by this Inflater. This method is limited to 32 bits; use getBytesRead() instead.

    • getTotalOut

      public int getTotalOut()
      Returns the total number of bytes written to the output buffer by this Inflater. The method is limited to 32 bits; use getBytesWritten() instead.

    • inflate

      public int inflate​(byte[] buf) throws DataFormatException
      Inflates bytes from the current input and stores them in buf.
      Parameters:
      buf - the buffer where decompressed data bytes are written.
      Returns:
      the number of bytes inflated.
      Throws:
      DataFormatException - if the underlying stream is corrupted or was not compressed using a Deflater.

    • inflate

      public int inflate​(byte[] buf, int offset, int byteCount) throws DataFormatException
      Inflates up to byteCount bytes from the current input and stores them in buf starting at offset.
      Returns:
      the number of bytes inflated.
      Throws:
      DataFormatException - if the underlying stream is corrupted or was not compressed using a Deflater.

    • needsDictionary

      public boolean needsDictionary()
      Returns true if the input bytes were compressed with a preset dictionary. This method should be called if the first call to inflate(byte[]) returns 0, to determine whether a dictionary is required. If so, setDictionary(byte[]) should be called with the appropriate dictionary before calling inflate again. Use getAdler() to determine which dictionary is required.

    • needsInput

      public boolean needsInput()
      Returns true if setInput(byte[]) must be called before inflation can continue.

    • reset

      public void reset()
      Resets this Inflater. Should be called prior to inflating a new set of data.

    • setDictionary

      public void setDictionary​(byte[] dictionary)
      Sets the preset dictionary to be used for inflation to dictionary. See needsDictionary for details.

    • setDictionary

      public void setDictionary​(byte[] dictionary, int offset, int byteCount)
      Sets the preset dictionary to be used for inflation to a subsequence of dictionary starting at offset and continuing for byteCount bytes. See needsDictionary for details.

    • setInput

      public void setInput​(byte[] buf)
      Sets the current input to to be decompressed. This method should only be called if needsInput() returns true.

    • setInput

      public void setInput​(byte[] buf, int offset, int byteCount)
      Sets the current input to to be decompressed. This method should only be called if needsInput() returns true.