UnicodeCompressor (ICU4J 75)

java.lang.Object
- com.ibm.icu.text.UnicodeCompressor

public final class UnicodeCompressor
extends Object

A compression engine implementing the Standard Compression Scheme for Unicode (SCSU) as outlined in Unicode Technical Report #6.

The SCSU works by using dynamically positioned windows consisting of 128 consecutive characters in Unicode. During compression, characters within a window are encoded in the compressed stream as the bytes 0x7F - 0xFF. The SCSU provides transparency for the characters (bytes) between U+0000 - U+00FF. The SCSU approximates the storage size of traditional character sets, for example 1 byte per character for ASCII or Latin-1 text, and 2 bytes per character for CJK ideographs.

USAGE

The static methods on UnicodeCompressor may be used in a straightforward manner to compress simple strings:

  String s = ... ; // get string from somewhere
  byte [] compressed = UnicodeCompressor.compress(s);

The static methods have a fairly large memory footprint. For finer-grained control over memory usage, UnicodeCompressor offers more powerful APIs allowing iterative compression:

  // Compress an array "chars" of length "len" using a buffer of 512 bytes
  // to the OutputStream "out"

  UnicodeCompressor myCompressor         = new UnicodeCompressor();
  final static int  BUFSIZE              = 512;
  byte []           byteBuffer           = new byte [ BUFSIZE ];
  int               bytesWritten         = 0;
  int []            unicharsRead         = new int [1];
  int               totalCharsCompressed = 0;
  int               totalBytesWritten    = 0;

  do {
    // do the compression
    bytesWritten = myCompressor.compress(chars, totalCharsCompressed, 
                                         len, unicharsRead,
                                         byteBuffer, 0, BUFSIZE);

    // do something with the current set of bytes
    out.write(byteBuffer, 0, bytesWritten);

    // update the no. of characters compressed
    totalCharsCompressed += unicharsRead[0];

    // update the no. of bytes written
    totalBytesWritten += bytesWritten;

  } while(totalCharsCompressed < len);

  myCompressor.reset(); // reuse compressor

Author:: Stephen F. Booth
See Also:: UnicodeDecompressor
Status:: Stable ICU 2.4.

Field Summary

Fields
Modifier and Type	Field and Description
`static int`	`ARMENIANINDEX`
`static int`	`COMPRESSIONOFFSET`
`static int`	`GREEKINDEX`
`static int`	`HALFWIDTHKATAKANAINDEX`
`static int`	`HIRAGANAINDEX`
`static int`	`INVALIDCHAR`
`static int`	`INVALIDWINDOW`
`static int`	`IPAEXTENSIONINDEX`
`static int`	`KATAKANAINDEX`
`static int`	`LATININDEX`
`static int`	`MAXINDEX`
`static int`	`NUMSTATICWINDOWS`
`static int`	`NUMWINDOWS`
`static int`	`RESERVEDINDEX`
`static int`	`SCHANGE0`
`static int`	`SCHANGE1`
`static int`	`SCHANGE2`
`static int`	`SCHANGE3`
`static int`	`SCHANGE4`
`static int`	`SCHANGE5`
`static int`	`SCHANGE6`
`static int`	`SCHANGE7`
`static int`	`SCHANGEU`
`static int`	`SDEFINE0`
`static int`	`SDEFINE1`
`static int`	`SDEFINE2`
`static int`	`SDEFINE3`
`static int`	`SDEFINE4`
`static int`	`SDEFINE5`
`static int`	`SDEFINE6`
`static int`	`SDEFINE7`
`static int`	`SDEFINEX`
`static int`	`SINGLEBYTEMODE`
`static int[]`	`sOffsets` Static compression window offsets
`static int[]`	`sOffsetTable` For window offset mapping
`static int`	`SQUOTE0`
`static int`	`SQUOTE1`
`static int`	`SQUOTE2`
`static int`	`SQUOTE3`
`static int`	`SQUOTE4`
`static int`	`SQUOTE5`
`static int`	`SQUOTE6`
`static int`	`SQUOTE7`
`static int`	`SQUOTEU`
`static int`	`SRESERVED`
`static int`	`UCHANGE0`
`static int`	`UCHANGE1`
`static int`	`UCHANGE2`
`static int`	`UCHANGE3`
`static int`	`UCHANGE4`
`static int`	`UCHANGE5`
`static int`	`UCHANGE6`
`static int`	`UCHANGE7`
`static int`	`UDEFINE0`
`static int`	`UDEFINE1`
`static int`	`UDEFINE2`
`static int`	`UDEFINE3`
`static int`	`UDEFINE4`
`static int`	`UDEFINE5`
`static int`	`UDEFINE6`
`static int`	`UDEFINE7`
`static int`	`UDEFINEX`
`static int`	`UNICODEMODE`
`static int`	`UQUOTEU`
`static int`	`URESERVED`

Constructor Summary

Constructors
Constructor and Description

UnicodeCompressor()
Create a UnicodeCompressor.

Constructors
Constructor and Description
`UnicodeCompressor()` Create a UnicodeCompressor.

Method Summary

All Methods Static Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`static byte[]`	`compress(char[] buffer, int start, int limit)` Compress a Unicode character array into a byte array.
`int`	`compress(char[] charBuffer, int charBufferStart, int charBufferLimit, int[] charsRead, byte[] byteBuffer, int byteBufferStart, int byteBufferLimit)` Compress a Unicode character array into a byte array.
`static byte[]`	`compress(String buffer)` Compress a string into a byte array.
`void`	`reset()` Reset the compressor to its initial state.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

- Field Detail
  - COMPRESSIONOFFSET
```
public static final int COMPRESSIONOFFSET
```
    See Also:
    
    Constant Field Values
  - NUMWINDOWS
```
public static final int NUMWINDOWS
```
    See Also:
    
    Constant Field Values
  - NUMSTATICWINDOWS
```
public static final int NUMSTATICWINDOWS
```
    See Also:
    
    Constant Field Values
  - INVALIDWINDOW
```
public static final int INVALIDWINDOW
```
    See Also:
    
    Constant Field Values
  - INVALIDCHAR
```
public static final int INVALIDCHAR
```
    See Also:
    
    Constant Field Values
  - SINGLEBYTEMODE
```
public static final int SINGLEBYTEMODE
```
    See Also:
    
    Constant Field Values
  - UNICODEMODE
```
public static final int UNICODEMODE
```
    See Also:
    
    Constant Field Values
  - MAXINDEX
```
public static final int MAXINDEX
```
    See Also:
    
    Constant Field Values
  - RESERVEDINDEX
```
public static final int RESERVEDINDEX
```
    See Also:
    
    Constant Field Values
  - LATININDEX
```
public static final int LATININDEX
```
    See Also:
    
    Constant Field Values
  - IPAEXTENSIONINDEX
```
public static final int IPAEXTENSIONINDEX
```
    See Also:
    
    Constant Field Values
  - GREEKINDEX
```
public static final int GREEKINDEX
```
    See Also:
    
    Constant Field Values
  - ARMENIANINDEX
```
public static final int ARMENIANINDEX
```
    See Also:
    
    Constant Field Values
  - HIRAGANAINDEX
```
public static final int HIRAGANAINDEX
```
    See Also:
    
    Constant Field Values
  - KATAKANAINDEX
```
public static final int KATAKANAINDEX
```
    See Also:
    
    Constant Field Values
  - HALFWIDTHKATAKANAINDEX
```
public static final int HALFWIDTHKATAKANAINDEX
```
    See Also:
    
    Constant Field Values
  - SDEFINEX
```
public static final int SDEFINEX
```
    See Also:
    
    Constant Field Values
  - SRESERVED
```
public static final int SRESERVED
```
    See Also:
    
    Constant Field Values
  - SQUOTEU
```
public static final int SQUOTEU
```
    See Also:
    
    Constant Field Values
  - SCHANGEU
```
public static final int SCHANGEU
```
    See Also:
    
    Constant Field Values
  - SQUOTE0
```
public static final int SQUOTE0
```
    See Also:
    
    Constant Field Values
  - SQUOTE1
```
public static final int SQUOTE1
```
    See Also:
    
    Constant Field Values
  - SQUOTE2
```
public static final int SQUOTE2
```
    See Also:
    
    Constant Field Values
  - SQUOTE3
```
public static final int SQUOTE3
```
    See Also:
    
    Constant Field Values
  - SQUOTE4
```
public static final int SQUOTE4
```
    See Also:
    
    Constant Field Values
  - SQUOTE5
```
public static final int SQUOTE5
```
    See Also:
    
    Constant Field Values
  - SQUOTE6
```
public static final int SQUOTE6
```
    See Also:
    
    Constant Field Values
  - SQUOTE7
```
public static final int SQUOTE7
```
    See Also:
    
    Constant Field Values
  - SCHANGE0
```
public static final int SCHANGE0
```
    See Also:
    
    Constant Field Values
  - SCHANGE1
```
public static final int SCHANGE1
```
    See Also:
    
    Constant Field Values
  - SCHANGE2
```
public static final int SCHANGE2
```
    See Also:
    
    Constant Field Values
  - SCHANGE3
```
public static final int SCHANGE3
```
    See Also:
    
    Constant Field Values
  - SCHANGE4
```
public static final int SCHANGE4
```
    See Also:
    
    Constant Field Values
  - SCHANGE5
```
public static final int SCHANGE5
```
    See Also:
    
    Constant Field Values
  - SCHANGE6
```
public static final int SCHANGE6
```
    See Also:
    
    Constant Field Values
  - SCHANGE7
```
public static final int SCHANGE7
```
    See Also:
    
    Constant Field Values
  - SDEFINE0
```
public static final int SDEFINE0
```
    See Also:
    
    Constant Field Values
  - SDEFINE1
```
public static final int SDEFINE1
```
    See Also:
    
    Constant Field Values
  - SDEFINE2
```
public static final int SDEFINE2
```
    See Also:
    
    Constant Field Values
  - SDEFINE3
```
public static final int SDEFINE3
```
    See Also:
    
    Constant Field Values
  - SDEFINE4
```
public static final int SDEFINE4
```
    See Also:
    
    Constant Field Values
  - SDEFINE5
```
public static final int SDEFINE5
```
    See Also:
    
    Constant Field Values
  - SDEFINE6
```
public static final int SDEFINE6
```
    See Also:
    
    Constant Field Values
  - SDEFINE7
```
public static final int SDEFINE7
```
    See Also:
    
    Constant Field Values
  - UCHANGE0
```
public static final int UCHANGE0
```
    See Also:
    
    Constant Field Values
  - UCHANGE1
```
public static final int UCHANGE1
```
    See Also:
    
    Constant Field Values
  - UCHANGE2
```
public static final int UCHANGE2
```
    See Also:
    
    Constant Field Values
  - UCHANGE3
```
public static final int UCHANGE3
```
    See Also:
    
    Constant Field Values
  - UCHANGE4
```
public static final int UCHANGE4
```
    See Also:
    
    Constant Field Values
  - UCHANGE5
```
public static final int UCHANGE5
```
    See Also:
    
    Constant Field Values
  - UCHANGE6
```
public static final int UCHANGE6
```
    See Also:
    
    Constant Field Values
  - UCHANGE7
```
public static final int UCHANGE7
```
    See Also:
    
    Constant Field Values
  - UDEFINE0
```
public static final int UDEFINE0
```
    See Also:
    
    Constant Field Values
  - UDEFINE1
```
public static final int UDEFINE1
```
    See Also:
    
    Constant Field Values
  - UDEFINE2
```
public static final int UDEFINE2
```
    See Also:
    
    Constant Field Values
  - UDEFINE3
```
public static final int UDEFINE3
```
    See Also:
    
    Constant Field Values
  - UDEFINE4
```
public static final int UDEFINE4
```
    See Also:
    
    Constant Field Values
  - UDEFINE5
```
public static final int UDEFINE5
```
    See Also:
    
    Constant Field Values
  - UDEFINE6
```
public static final int UDEFINE6
```
    See Also:
    
    Constant Field Values
  - UDEFINE7
```
public static final int UDEFINE7
```
    See Also:
    
    Constant Field Values
  - UQUOTEU
```
public static final int UQUOTEU
```
    See Also:
    
    Constant Field Values
  - UDEFINEX
```
public static final int UDEFINEX
```
    See Also:
    
    Constant Field Values
  - URESERVED
```
public static final int URESERVED
```
    See Also:
    
    Constant Field Values
  - sOffsetTable
```
public static final int[] sOffsetTable
```
    For window offset mapping
  - sOffsets
```
public static final int[] sOffsets
```
    Static compression window offsets
- Constructor Detail
  - UnicodeCompressor
```
public UnicodeCompressor()
```
    Create a UnicodeCompressor. Sets all windows to their default values.
    
    See Also:
    
    reset()
    
    Status:
    Stable ICU 2.4.
- Method Detail
  - compress
```
public static byte[] compress(String buffer)
```
    Compress a string into a byte array.
    
    Parameters:
    
    buffer - The string to compress.
    
    Returns:
    
    A byte array containing the compressed characters.
    
    See Also:
    
    compress(char [], int, int)
    
    Status:
    Stable ICU 2.4.
  - compress
```
public static byte[] compress(char[] buffer,
                              int start,
                              int limit)
```
    Compress a Unicode character array into a byte array.
    
    Parameters:
    
    buffer - The character buffer to compress.
    
    start - The start of the character run to compress.
    
    limit - The limit of the character run to compress.
    
    Returns:
    
    A byte array containing the compressed characters.
    
    See Also:
    
    compress(String)
    
    Status:
    Stable ICU 2.4.
  - compress
```
public int compress(char[] charBuffer,
                    int charBufferStart,
                    int charBufferLimit,
                    int[] charsRead,
                    byte[] byteBuffer,
                    int byteBufferStart,
                    int byteBufferLimit)
```
    Compress a Unicode character array into a byte array. This function will only consume input that can be completely output.
    
    Parameters:
    
    charBuffer - The character buffer to compress.
    
    charBufferStart - The start of the character run to compress.
    
    charBufferLimit - The limit of the character run to compress.
    
    charsRead - A one-element array. If not null, on return the number of characters read from charBuffer.
    
    byteBuffer - A buffer to receive the compressed data. This buffer must be at minimum four bytes in size.
    
    byteBufferStart - The starting offset to which to write compressed data.
    
    byteBufferLimit - The limiting offset for writing compressed data.
    
    Returns:
    
    The number of bytes written to byteBuffer.
    
    Status:
    Stable ICU 2.4.
  - reset
```
public void reset()
```
    Reset the compressor to its initial state.
    
    Status:
    Stable ICU 2.4.

Class UnicodeCompressor

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

COMPRESSIONOFFSET

NUMWINDOWS

NUMSTATICWINDOWS

INVALIDWINDOW

INVALIDCHAR

SINGLEBYTEMODE

UNICODEMODE

MAXINDEX

RESERVEDINDEX

LATININDEX

IPAEXTENSIONINDEX

GREEKINDEX

ARMENIANINDEX

HIRAGANAINDEX

KATAKANAINDEX

HALFWIDTHKATAKANAINDEX

SDEFINEX

SRESERVED

SQUOTEU

SCHANGEU

SQUOTE0

SQUOTE1

SQUOTE2

SQUOTE3

SQUOTE4

SQUOTE5

SQUOTE6

SQUOTE7

SCHANGE0

SCHANGE1

SCHANGE2

SCHANGE3

SCHANGE4

SCHANGE5

SCHANGE6

SCHANGE7

SDEFINE0

SDEFINE1

SDEFINE2

SDEFINE3

SDEFINE4

SDEFINE5

SDEFINE6

SDEFINE7

UCHANGE0

UCHANGE1

UCHANGE2

UCHANGE3

UCHANGE4

UCHANGE5

UCHANGE6

UCHANGE7

UDEFINE0

UDEFINE1

UDEFINE2

UDEFINE3

UDEFINE4

UDEFINE5

UDEFINE6

UDEFINE7

UQUOTEU

UDEFINEX

URESERVED

sOffsetTable

sOffsets

Constructor Detail

UnicodeCompressor

Method Detail

compress

compress

compress

reset