com.ibm.icu.text

Class UnicodeDecompressor

java.lang.Object

com.ibm.icu.text.UnicodeDecompressor

public final class UnicodeDecompressor
extends Object

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

USAGE

The static methods on UnicodeDecompressor may be used in a straightforward manner to decompress simple strings:

  byte [] compressed = ... ; // get compressed bytes from somewhere
  String result = UnicodeDecompressor.decompress(compressed);
 

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

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

  UnicodeDecompressor myDecompressor         = new UnicodeDecompressor();
  final static int    BUFSIZE                = 512;
  char []             charBuffer             = new char [ BUFSIZE ];
  int                 charsWritten           = 0;
  int []              bytesRead              = new int [1];
  int                 totalBytesDecompressed = 0;
  int                 totalCharsWritten      = 0;

  do {
    // do the decompression
    charsWritten = myDecompressor.decompress(bytes, totalBytesDecompressed, 
                                             len, bytesRead,
                                             charBuffer, 0, BUFSIZE);

    // do something with the current set of chars
    out.write(charBuffer, 0, charsWritten);

    // update the no. of bytes decompressed
    totalBytesDecompressed += bytesRead[0];

    // update the no. of chars written
    totalCharsWritten += charsWritten;

  } while(totalBytesDecompressed < len);

  myDecompressor.reset(); // reuse decompressor
 

Decompression is performed according to the standard set forth in Unicode Technical Report #6

Author:

Stephen F. Booth

See Also:

UnicodeCompressor

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
UnicodeDecompressor() Create a UnicodeDecompressor.

Method Summary

Methods

Modifier and Type	Method and Description
static String	decompress(byte[] buffer) Decompress a byte array into a String.
static char[]	decompress(byte[] buffer, int start, int limit) Decompress a byte array into a Unicode character array.
int	decompress(byte[] byteBuffer, int byteBufferStart, int byteBufferLimit, int[] bytesRead, char[] charBuffer, int charBufferStart, int charBufferLimit) Decompress a byte array into a Unicode character array.
void	reset() Reset the decompressor 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

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Constant Field Values

NUMSTATICWINDOWS

public static final int NUMSTATICWINDOWS

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Constant Field Values

INVALIDWINDOW

public static final int INVALIDWINDOW

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Constant Field Values

INVALIDCHAR

public static final int INVALIDCHAR

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Constant Field Values

SINGLEBYTEMODE

public static final int SINGLEBYTEMODE

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Constant Field Values

UNICODEMODE

public static final int UNICODEMODE

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Constant Field Values

MAXINDEX

public static final int MAXINDEX

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Constant Field Values

RESERVEDINDEX

public static final int RESERVEDINDEX

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Constant Field Values

LATININDEX

public static final int LATININDEX

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Constant Field Values

IPAEXTENSIONINDEX

public static final int IPAEXTENSIONINDEX

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Constant Field Values

GREEKINDEX

public static final int GREEKINDEX

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Constant Field Values

ARMENIANINDEX

public static final int ARMENIANINDEX

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Constant Field Values

HIRAGANAINDEX

public static final int HIRAGANAINDEX

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Constant Field Values

KATAKANAINDEX

public static final int KATAKANAINDEX

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Constant Field Values

HALFWIDTHKATAKANAINDEX

public static final int HALFWIDTHKATAKANAINDEX

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Constant Field Values

SDEFINEX

public static final int SDEFINEX

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Constant Field Values

SRESERVED

public static final int SRESERVED

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Constant Field Values

SQUOTEU

public static final int SQUOTEU

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Constant Field Values

SCHANGEU

public static final int SCHANGEU

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Constant Field Values

SQUOTE0

public static final int SQUOTE0

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Constant Field Values

SQUOTE1

public static final int SQUOTE1

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Constant Field Values

SQUOTE2

public static final int SQUOTE2

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Constant Field Values

SQUOTE3

public static final int SQUOTE3

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Constant Field Values

SQUOTE4

public static final int SQUOTE4

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Constant Field Values

SQUOTE5

public static final int SQUOTE5

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Constant Field Values

SQUOTE6

public static final int SQUOTE6

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Constant Field Values

SQUOTE7

public static final int SQUOTE7

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Constant Field Values

SCHANGE0

public static final int SCHANGE0

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Constant Field Values

SCHANGE1

public static final int SCHANGE1

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Constant Field Values

SCHANGE2

public static final int SCHANGE2

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Constant Field Values

SCHANGE3

public static final int SCHANGE3

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Constant Field Values

SCHANGE4

public static final int SCHANGE4

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Constant Field Values

SCHANGE5

public static final int SCHANGE5

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Constant Field Values

SCHANGE6

public static final int SCHANGE6

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Constant Field Values

SCHANGE7

public static final int SCHANGE7

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Constant Field Values

SDEFINE0

public static final int SDEFINE0

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Constant Field Values

SDEFINE1

public static final int SDEFINE1

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Constant Field Values

SDEFINE2

public static final int SDEFINE2

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Constant Field Values

SDEFINE3

public static final int SDEFINE3

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Constant Field Values

SDEFINE4

public static final int SDEFINE4

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Constant Field Values

SDEFINE5

public static final int SDEFINE5

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Constant Field Values

SDEFINE6

public static final int SDEFINE6

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Constant Field Values

SDEFINE7

public static final int SDEFINE7

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Constant Field Values

UCHANGE0

public static final int UCHANGE0

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Constant Field Values

UCHANGE1

public static final int UCHANGE1

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Constant Field Values

UCHANGE2

public static final int UCHANGE2

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Constant Field Values

UCHANGE3

public static final int UCHANGE3

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Constant Field Values

UCHANGE4

public static final int UCHANGE4

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UCHANGE5

public static final int UCHANGE5

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UCHANGE6

public static final int UCHANGE6

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UCHANGE7

public static final int UCHANGE7

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Constant Field Values

UDEFINE0

public static final int UDEFINE0

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Constant Field Values

UDEFINE1

public static final int UDEFINE1

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UDEFINE2

public static final int UDEFINE2

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Constant Field Values

UDEFINE3

public static final int UDEFINE3

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Constant Field Values

UDEFINE4

public static final int UDEFINE4

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Constant Field Values

UDEFINE5

public static final int UDEFINE5

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Constant Field Values

UDEFINE6

public static final int UDEFINE6

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Constant Field Values

UDEFINE7

public static final int UDEFINE7

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Constant Field Values

UQUOTEU

public static final int UQUOTEU

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Constant Field Values

UDEFINEX

public static final int UDEFINEX

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Constant Field Values

URESERVED

public static final int URESERVED

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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

UnicodeDecompressor

public UnicodeDecompressor()

Create a UnicodeDecompressor. Sets all windows to their default values.

See Also:

reset()

Status:

Stable ICU 2.4.

Method Detail

decompress

public static String decompress(byte[] buffer)

Decompress a byte array into a String.

Parameters:

buffer - The byte array to decompress.

Returns:

A String containing the decompressed characters.

See Also:

decompress(byte [], int, int)

Status:

Stable ICU 2.4.

decompress

public static char[] decompress(byte[] buffer,
                int start,
                int limit)

Decompress a byte array into a Unicode character array.

Parameters:

buffer - The byte array to decompress.

start - The start of the byte run to decompress.

limit - The limit of the byte run to decompress.

Returns:

A character array containing the decompressed bytes.

See Also:

decompress(byte [])

Status:

Stable ICU 2.4.

decompress

public int decompress(byte[] byteBuffer,
             int byteBufferStart,
             int byteBufferLimit,
             int[] bytesRead,
             char[] charBuffer,
             int charBufferStart,
             int charBufferLimit)

Decompress a byte array into a Unicode character array. This function will either completely fill the output buffer, or consume the entire input.

Parameters:

byteBuffer - The byte buffer to decompress.

byteBufferStart - The start of the byte run to decompress.

byteBufferLimit - The limit of the byte run to decompress.

bytesRead - A one-element array. If not null, on return the number of bytes read from byteBuffer.

charBuffer - A buffer to receive the decompressed data. This buffer must be at minimum two characters in size.

charBufferStart - The starting offset to which to write decompressed data.

charBufferLimit - The limiting offset for writing decompressed data.

Returns:

The number of Unicode characters written to charBuffer.

Status:

Stable ICU 2.4.

reset

public void reset()

Reset the decompressor to its initial state.

Status:

Stable ICU 2.4.