Deflater
open class Deflater
kotlin.Any | |
↳ | java.util.zip.Deflater |
This class provides support for general purpose compression 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 deflates sequences of bytes into ZLIB compressed data format. 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); compresser.end(); // 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 }
Summary
Constants | |
---|---|
static Int |
Compression level for best compression. |
static Int |
Compression level for fastest compression. |
static Int |
Default compression level. |
static Int |
Default compression strategy. |
static Int |
Compression method for the deflate algorithm (the only one currently supported). |
static Int |
Compression strategy best used for data consisting mostly of small values with a somewhat random distribution. |
static Int |
Compression flush mode used to flush out all pending output and reset the deflater. |
static Int |
Compression strategy for Huffman coding only. |
static Int |
Compression level for no compression. |
static Int |
Compression flush mode used to achieve best compression result. |
static Int |
Compression flush mode used to flush out all pending output; may degrade compression for some compression algorithms. |
Public constructors | |
---|---|
Creates a new compressor using the specified compression level. |
|
Creates a new compressor using the specified compression level. |
|
Deflater() Creates a new compressor with the default compression level. |
Public methods | |
---|---|
open Int |
Compresses the input data and fills specified buffer with compressed data. |
open Int |
Compresses the input data and fills specified buffer with compressed data. |
open Int |
deflate(output: ByteBuffer!) Compresses the input data and fills specified buffer with compressed data. |
open Int |
Compresses the input data and fills the specified buffer with compressed data. |
open Int |
deflate(output: ByteBuffer!, flush: Int) Compresses the input data and fills the specified buffer with compressed data. |
open Unit |
end() Closes the compressor and discards any unprocessed input. |
open Unit |
finish() When called, indicates that compression should end with the current contents of the input buffer. |
open Boolean |
finished() Returns true if the end of the compressed data output stream has been reached. |
open Int |
getAdler() Returns the ADLER-32 value of the uncompressed data. |
open Long |
Returns the total number of uncompressed bytes input so far. |
open Long |
Returns the total number of compressed bytes output so far. |
open Int |
Returns the total number of uncompressed bytes input so far. |
open Int |
Returns the total number of compressed bytes output so far. |
open Boolean |
Returns true if no data remains in the input buffer. |
open Unit |
reset() Resets deflater so that a new set of input data can be processed. |
open Unit |
setDictionary(dictionary: ByteArray!, off: Int, len: Int) Sets preset dictionary for compression. |
open Unit |
setDictionary(dictionary: ByteArray!) Sets preset dictionary for compression. |
open Unit |
setDictionary(dictionary: ByteBuffer!) Sets preset dictionary for compression. |
open Unit |
Sets input data for compression. |
open Unit |
Sets input data for compression. |
open Unit |
setInput(input: ByteBuffer!) Sets input data for compression. |
open Unit |
Sets the compression level to the specified value. |
open Unit |
setStrategy(strategy: Int) Sets the compression strategy to the specified value. |
Constants
BEST_COMPRESSION
static val BEST_COMPRESSION: Int
Compression level for best compression.
Value: 9
BEST_SPEED
static val BEST_SPEED: Int
Compression level for fastest compression.
Value: 1
DEFAULT_COMPRESSION
static val DEFAULT_COMPRESSION: Int
Default compression level.
Value: -1
DEFAULT_STRATEGY
static val DEFAULT_STRATEGY: Int
Default compression strategy.
Value: 0
DEFLATED
static val DEFLATED: Int
Compression method for the deflate algorithm (the only one currently supported).
Value: 8
FILTERED
static val FILTERED: Int
Compression strategy best used for data consisting mostly of small values with a somewhat random distribution. Forces more Huffman coding and less string matching.
Value: 1
FULL_FLUSH
static val FULL_FLUSH: Int
Compression flush mode used to flush out all pending output and reset the deflater. Using this mode too often can seriously degrade compression.
Value: 3
HUFFMAN_ONLY
static val HUFFMAN_ONLY: Int
Compression strategy for Huffman coding only.
Value: 2
NO_COMPRESSION
static val NO_COMPRESSION: Int
Compression level for no compression.
Value: 0
NO_FLUSH
static val NO_FLUSH: Int
Compression flush mode used to achieve best compression result.
Value: 0
SYNC_FLUSH
static val SYNC_FLUSH: Int
Compression flush mode used to flush out all pending output; may degrade compression for some compression algorithms.
Value: 2
Public constructors
Deflater
Deflater(
level: Int,
nowrap: Boolean)
Creates a new compressor using the specified compression level. If 'nowrap' is true then the ZLIB header and checksum fields will not be used in order to support the compression format used in both GZIP and PKZIP.
Parameters | |
---|---|
level |
Int: the compression level (0-9) |
nowrap |
Boolean: if true then use GZIP compatible compression |
Deflater
Deflater(level: Int)
Creates a new compressor using the specified compression level. Compressed data will be generated in ZLIB format.
Parameters | |
---|---|
level |
Int: the compression level (0-9) |
Deflater
Deflater()
Creates a new compressor with the default compression level. Compressed data will be generated in ZLIB format.
Public methods
deflate
open fun deflate(
output: ByteArray!,
off: Int,
len: Int
): Int
Compresses the input data and fills specified buffer with compressed data. Returns actual number of bytes of compressed data. A return value of 0 indicates that needsInput
should be called in order to determine if more input data is required.
This method uses NO_FLUSH
as its compression flush mode. An invocation of this method of the form deflater.deflate(b, off, len)
yields the same result as the invocation of deflater.deflate(b, off, len, Deflater.NO_FLUSH)
.
Parameters | |
---|---|
output |
ByteArray!: the buffer for the compressed data |
off |
Int: the start offset of the data |
len |
Int: the maximum number of bytes of compressed data |
Return | |
---|---|
Int |
the actual number of bytes of compressed data written to the output buffer |
deflate
open fun deflate(output: ByteArray!): Int
Compresses the input data and fills specified buffer with compressed data. Returns actual number of bytes of compressed data. A return value of 0 indicates that needsInput
should be called in order to determine if more input data is required.
This method uses NO_FLUSH
as its compression flush mode. An invocation of this method of the form deflater.deflate(b)
yields the same result as the invocation of deflater.deflate(b, 0, b.length, Deflater.NO_FLUSH)
.
Parameters | |
---|---|
output |
ByteArray!: the buffer for the compressed data |
Return | |
---|---|
Int |
the actual number of bytes of compressed data written to the output buffer |
deflate
open fun deflate(output: ByteBuffer!): Int
Compresses the input data and fills specified buffer with compressed data. Returns actual number of bytes of compressed data. A return value of 0 indicates that needsInput
should be called in order to determine if more input data is required.
This method uses NO_FLUSH
as its compression flush mode. An invocation of this method of the form deflater.deflate(output)
yields the same result as the invocation of deflater.deflate(output, Deflater.NO_FLUSH)
.
Parameters | |
---|---|
output |
ByteBuffer!: the buffer for the compressed data |
Return | |
---|---|
Int |
the actual number of bytes of compressed data written to the output buffer |
deflate
open fun deflate(
output: ByteArray!,
off: Int,
len: Int,
flush: Int
): Int
Compresses the input data and fills the specified buffer with compressed data. Returns actual number of bytes of data compressed.
Compression flush mode is one of the following three modes:
NO_FLUSH
: allows the deflater to decide how much data to accumulate, before producing output, in order to achieve the best compression (should be used in normal use scenario). A return value of 0 in this flush mode indicates thatneedsInput()
should be called in order to determine if more input data is required.SYNC_FLUSH
: all pending output in the deflater is flushed, to the specified output buffer, so that an inflater that works on compressed data can get all input data available so far (In particular theneedsInput()
returnstrue
after this invocation if enough output space is provided). Flushing withSYNC_FLUSH
may degrade compression for some compression algorithms and so it should be used only when necessary.FULL_FLUSH
: all pending output is flushed out as withSYNC_FLUSH
. The compression state is reset so that the inflater that works on the compressed output data can restart from this point if previous compressed data has been damaged or if random access is desired. UsingFULL_FLUSH
too often can seriously degrade compression.
In the case of FULL_FLUSH
or SYNC_FLUSH
, if the return value is len
, the space available in output buffer b
, this method should be invoked again with the same flush
parameter and more output space. Make sure that len
is greater than 6 to avoid flush marker (5 bytes) being repeatedly output to the output buffer every time this method is invoked.
If the setInput(java.nio.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.
Parameters | |
---|---|
output |
ByteArray!: the buffer for the compressed data |
off |
Int: the start offset of the data |
len |
Int: the maximum number of bytes of compressed data |
flush |
Int: the compression flush mode |
Return | |
---|---|
Int |
the actual number of bytes of compressed data written to the output buffer |
Exceptions | |
---|---|
java.lang.IllegalArgumentException |
if the flush mode is invalid |
deflate
open fun deflate(
output: ByteBuffer!,
flush: Int
): Int
Compresses the input data and fills the specified buffer with compressed data. Returns actual number of bytes of data compressed.
Compression flush mode is one of the following three modes:
NO_FLUSH
: allows the deflater to decide how much data to accumulate, before producing output, in order to achieve the best compression (should be used in normal use scenario). A return value of 0 in this flush mode indicates thatneedsInput()
should be called in order to determine if more input data is required.SYNC_FLUSH
: all pending output in the deflater is flushed, to the specified output buffer, so that an inflater that works on compressed data can get all input data available so far (In particular theneedsInput()
returnstrue
after this invocation if enough output space is provided). Flushing withSYNC_FLUSH
may degrade compression for some compression algorithms and so it should be used only when necessary.FULL_FLUSH
: all pending output is flushed out as withSYNC_FLUSH
. The compression state is reset so that the inflater that works on the compressed output data can restart from this point if previous compressed data has been damaged or if random access is desired. UsingFULL_FLUSH
too often can seriously degrade compression.
In the case of FULL_FLUSH
or SYNC_FLUSH
, if the return value is equal to the remaining space of the buffer, this method should be invoked again with the same flush
parameter and more output space. Make sure that the buffer has at least 6 bytes of remaining space to avoid the flush marker (5 bytes) being repeatedly output to the output buffer every time this method is invoked.
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.
If the setInput(java.nio.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.
Parameters | |
---|---|
output |
ByteBuffer!: the buffer for the compressed data |
flush |
Int: the compression flush mode |
Return | |
---|---|
Int |
the actual number of bytes of compressed data written to the output buffer |
Exceptions | |
---|---|
java.lang.IllegalArgumentException |
if the flush mode is invalid |
end
open fun end(): Unit
Closes the compressor and discards any unprocessed input. This method should be called when the compressor is no longer being used. Once this method is called, the behavior of the Deflater object is undefined.
finish
open fun finish(): Unit
When called, indicates that compression should end with the current contents of the input buffer.
finished
open fun finished(): Boolean
Returns true if the end of the compressed data output stream has been reached.
Return | |
---|---|
Boolean |
true if the end of the compressed data output stream has been reached |
getAdler
open fun getAdler(): Int
Returns the ADLER-32 value of the uncompressed data.
Return | |
---|---|
Int |
the ADLER-32 value of the uncompressed data |
getBytesRead
open fun getBytesRead(): Long
Returns the total number of uncompressed bytes input so far.
Return | |
---|---|
Long |
the total (non-negative) number of uncompressed bytes input so far |
getBytesWritten
open fun getBytesWritten(): Long
Returns the total number of compressed bytes output so far.
Return | |
---|---|
Long |
the total (non-negative) number of compressed bytes output so far |
getTotalIn
open fun getTotalIn(): Int
Returns the total number of uncompressed 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.
Return | |
---|---|
Int |
the total number of uncompressed bytes input so far |
getTotalOut
open fun getTotalOut(): Int
Returns the total number of compressed 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.
Return | |
---|---|
Int |
the total number of compressed bytes output so far |
needsInput
open fun needsInput(): Boolean
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.
Return | |
---|---|
Boolean |
true if the input data buffer is empty and setInput() should be called in order to provide more input |
reset
open fun reset(): Unit
Resets deflater so that a new set of input data can be processed. Keeps current compression level and strategy settings.
setDictionary
open fun setDictionary(
dictionary: ByteArray!,
off: Int,
len: Int
): Unit
Sets preset dictionary for compression. A preset dictionary is used when the history buffer can be predetermined. When the data is later uncompressed with Inflater.inflate(), Inflater.getAdler() can be called in order to get the Adler-32 value of the dictionary required for decompression.
Parameters | |
---|---|
dictionary |
ByteArray!: the dictionary data bytes |
off |
Int: the start offset of the data |
len |
Int: the length of the data |
See Also
setDictionary
open fun setDictionary(dictionary: ByteArray!): Unit
Sets preset dictionary for compression. A preset dictionary is used when the history buffer can be predetermined. When the data is later uncompressed with Inflater.inflate(), Inflater.getAdler() can be called in order to get the Adler-32 value of the dictionary required for decompression.
Parameters | |
---|---|
dictionary |
ByteArray!: the dictionary data bytes |
See Also
setDictionary
open fun setDictionary(dictionary: ByteBuffer!): Unit
Sets preset dictionary for compression. A preset dictionary is used when the history buffer can be predetermined. When the data is later uncompressed with Inflater.inflate(), Inflater.getAdler() can be called in order to get the Adler-32 value of the dictionary required for decompression.
The bytes in given byte buffer will be fully consumed by this method. On return, its position will equal its limit.
Parameters | |
---|---|
dictionary |
ByteBuffer!: the dictionary data bytes |
See Also
setInput
open fun setInput(
input: ByteArray!,
off: Int,
len: Int
): Unit
Sets input data for compression.
One of the setInput()
methods should be called whenever needsInput()
returns true indicating that more input data is required.
Parameters | |
---|---|
input |
ByteArray!: the input data bytes |
off |
Int: the start offset of the data |
len |
Int: the length of the data |
See Also
setInput
open fun setInput(input: ByteArray!): Unit
Sets input data for compression.
One of the setInput()
methods should be called whenever needsInput()
returns true indicating that more input data is required.
Parameters | |
---|---|
input |
ByteArray!: the input data bytes |
See Also
setInput
open fun setInput(input: ByteBuffer!): Unit
Sets input data for compression.
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 deflate operations are performed, up to the buffer's limit. The input buffer may be modified (refilled) between deflate 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 deflate operation will result in undefined behavior, which may include incorrect operation results or operation failure.
Parameters | |
---|---|
input |
ByteBuffer!: the input data bytes |
See Also
setLevel
open fun setLevel(level: Int): Unit
Sets the compression level to the specified value.
If the compression level is changed, the next invocation of deflate
will compress the input available so far with the old level (and may be flushed); the new level will take effect only after that invocation.
Parameters | |
---|---|
level |
Int: the new compression level (0-9) |
Exceptions | |
---|---|
java.lang.IllegalArgumentException |
if the compression level is invalid |
setStrategy
open fun setStrategy(strategy: Int): Unit
Sets the compression strategy to the specified value.
If the compression strategy is changed, the next invocation of deflate
will compress the input available so far with the old strategy (and may be flushed); the new strategy will take effect only after that invocation.
Parameters | |
---|---|
strategy |
Int: the new compression strategy |
Exceptions | |
---|---|
java.lang.IllegalArgumentException |
if the compression strategy is invalid |