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
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\u20AC\u20AC";
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
}
Method from java.util.zip.Inflater Detail: |
public void end() {
synchronized (zsRef) {
long addr = zsRef.address();
zsRef.clear();
if (addr != 0) {
end(addr);
buf = null;
}
}
}
Closes the decompressor and discards any unprocessed input.
This method should be called when the decompressor is no longer
being used, but will also be called automatically by the finalize()
method. Once this method is called, the behavior of the Inflater
object is undefined. |
boolean ended() {
synchronized (zsRef) {
return zsRef.address() == 0;
}
}
|
protected void finalize() {
end();
}
Closes the decompressor when garbage is collected. |
public boolean finished() {
synchronized (zsRef) {
return finished;
}
}
Returns true if the end of the compressed data stream has been
reached. |
public int getAdler() {
synchronized (zsRef) {
ensureOpen();
return getAdler(zsRef.address());
}
}
Returns the ADLER-32 value of the uncompressed data. |
public long getBytesRead() {
synchronized (zsRef) {
ensureOpen();
return getBytesRead(zsRef.address());
}
}
Returns the total number of compressed bytes input so far. |
public long getBytesWritten() {
synchronized (zsRef) {
ensureOpen();
return getBytesWritten(zsRef.address());
}
}
Returns the total number of uncompressed bytes output so far. |
public int getRemaining() {
synchronized (zsRef) {
return len;
}
}
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. |
public int getTotalIn() {
return (int) getBytesRead();
}
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. |
public int getTotalOut() {
return (int) getBytesWritten();
}
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. |
public int inflate(byte[] b) throws DataFormatException {
return inflate(b, 0, b.length);
}
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. |
public int inflate(byte[] b,
int off,
int len) throws DataFormatException {
if (b == null) {
throw new NullPointerException();
}
if (off < 0 || len < 0 || off > b.length - len) {
throw new ArrayIndexOutOfBoundsException();
}
synchronized (zsRef) {
ensureOpen();
return inflateBytes(zsRef.address(), b, off, len);
}
}
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. |
public boolean needsDictionary() {
synchronized (zsRef) {
return needDict;
}
}
Returns true if a preset dictionary is needed for decompression. |
public boolean needsInput() {
synchronized (zsRef) {
return len < = 0;
}
}
Returns true if no data remains in the input buffer. This can
be used to determine if #setInput should be called in order
to provide more input. |
public void reset() {
synchronized (zsRef) {
ensureOpen();
reset(zsRef.address());
buf = defaultBuf;
finished = false;
needDict = false;
off = len = 0;
}
}
Resets inflater so that a new set of input data can be processed. |
public void setDictionary(byte[] b) {
setDictionary(b, 0, b.length);
}
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. |
public void setDictionary(byte[] b,
int off,
int len) {
if (b == null) {
throw new NullPointerException();
}
if (off < 0 || len < 0 || off > b.length - len) {
throw new ArrayIndexOutOfBoundsException();
}
synchronized (zsRef) {
ensureOpen();
setDictionary(zsRef.address(), b, off, len);
needDict = false;
}
}
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. |
public void setInput(byte[] b) {
setInput(b, 0, b.length);
}
Sets input data for decompression. Should be called whenever
needsInput() returns true indicating that more input data is
required. |
public void setInput(byte[] b,
int off,
int len) {
if (b == null) {
throw new NullPointerException();
}
if (off < 0 || len < 0 || off > b.length - len) {
throw new ArrayIndexOutOfBoundsException();
}
synchronized (zsRef) {
this.buf = b;
this.off = off;
this.len = len;
}
}
Sets input data for decompression. Should be called whenever
needsInput() returns true indicating that more input data is
required. |