org.apache.lucene.util

Class IndexableBinaryStringTools

java.lang.Object

org.apache.lucene.util.IndexableBinaryStringTools

public final class IndexableBinaryStringTools
extends Object

Provides support for converting byte sequences to Strings and back again. The resulting Strings preserve the original byte sequences' sort order.

The Strings are constructed using a Base 8000h encoding of the original binary data - each char of an encoded String represents a 15-bit chunk from the byte sequence. Base 8000h was chosen because it allows for all lower 15 bits of char to be used without restriction; the surrogate range [U+D8000-U+DFFF] does not represent valid chars, and would require complicated handling to avoid them and allow use of char's high bit.

Although unset bits are used as padding in the final char, the original byte sequence could contain trailing bytes with no set bits (null bytes): padding is indistinguishable from valid information. To overcome this problem, a char is appended, indicating the number of encoded bytes in the final content char.

Some methods in this class are defined over CharBuffers and ByteBuffers, but these are deprecated in favor of methods that operate directly on byte[] and char[] arrays. Note that this class calls array() and arrayOffset() on the CharBuffers and ByteBuffers it uses, so only wrapped arrays may be used. This class interprets the arrayOffset() and limit() values returned by its input buffers as beginning and end+1 positions on the wrapped array, respectively; similarly, on the output buffer, arrayOffset() is the first position written to, and limit() is set to one past the final output array position.

WARNING: This means that the deprecated Buffer-based methods only work correctly with buffers that have an offset of 0. For example, they will not correctly interpret buffers returned by ByteBuffer.slice().

WARNING: This API is experimental and might change in incompatible ways in the next release.

Method Summary

Methods

Modifier and Type	Method and Description
static void	decode(char[] inputArray, int inputOffset, int inputLength, byte[] outputArray, int outputOffset, int outputLength) Decodes the input char sequence into the output byte sequence.
static ByteBuffer	decode(CharBuffer input) Deprecated. Use decode(char[], int, int, byte[], int, int) instead. This method will be removed in Lucene 4.0
static void	decode(CharBuffer input, ByteBuffer output) Deprecated. Use decode(char[], int, int, byte[], int, int) instead. This method will be removed in Lucene 4.0
static void	encode(byte[] inputArray, int inputOffset, int inputLength, char[] outputArray, int outputOffset, int outputLength) Encodes the input byte sequence into the output char sequence.
static CharBuffer	encode(ByteBuffer input) Deprecated. Use encode(byte[], int, int, char[], int, int) instead. This method will be removed in Lucene 4.0
static void	encode(ByteBuffer input, CharBuffer output) Deprecated. Use encode(byte[], int, int, char[], int, int) instead. This method will be removed in Lucene 4.0
static int	getDecodedLength(char[] encoded, int offset, int length) Returns the number of bytes required to decode the given char sequence.
static int	getDecodedLength(CharBuffer encoded) Deprecated. Use getDecodedLength(char[], int, int) instead. This method will be removed in Lucene 4.0
static int	getEncodedLength(byte[] inputArray, int inputOffset, int inputLength) Returns the number of chars required to encode the given bytes.
static int	getEncodedLength(ByteBuffer original) Deprecated. Use getEncodedLength(byte[], int, int) instead. This method will be removed in Lucene 4.0

Methods inherited from class java.lang.Object

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

Method Detail

getEncodedLength

@Deprecated
public static int getEncodedLength(ByteBuffer original)
                            throws IllegalArgumentException

Deprecated. Use getEncodedLength(byte[], int, int) instead. This method will be removed in Lucene 4.0

Returns the number of chars required to encode the given byte sequence.

Parameters:

original - The byte sequence to be encoded. Must be backed by an array.

Returns:

The number of chars required to encode the given byte sequence

Throws:

IllegalArgumentException - If the given ByteBuffer is not backed by an array

getEncodedLength

public static int getEncodedLength(byte[] inputArray,
                   int inputOffset,
                   int inputLength)

Returns the number of chars required to encode the given bytes.

Parameters:

inputArray - byte sequence to be encoded

inputOffset - initial offset into inputArray

inputLength - number of bytes in inputArray

Returns:

The number of chars required to encode the number of bytes.

getDecodedLength

@Deprecated
public static int getDecodedLength(CharBuffer encoded)
                            throws IllegalArgumentException

Deprecated. Use getDecodedLength(char[], int, int) instead. This method will be removed in Lucene 4.0

Returns the number of bytes required to decode the given char sequence.

Parameters:

encoded - The char sequence to be decoded. Must be backed by an array.

Returns:

The number of bytes required to decode the given char sequence

Throws:

IllegalArgumentException - If the given CharBuffer is not backed by an array

getDecodedLength

public static int getDecodedLength(char[] encoded,
                   int offset,
                   int length)

Returns the number of bytes required to decode the given char sequence.

Parameters:

encoded - char sequence to be decoded

offset - initial offset

length - number of characters

Returns:

The number of bytes required to decode the given char sequence

encode

@Deprecated
public static void encode(ByteBuffer input,
                     CharBuffer output)

Deprecated. Use encode(byte[], int, int, char[], int, int) instead. This method will be removed in Lucene 4.0

Encodes the input byte sequence into the output char sequence. Before calling this method, ensure that the output CharBuffer has sufficient capacity by calling getEncodedLength(java.nio.ByteBuffer).

Parameters:

input - The byte sequence to encode

output - Where the char sequence encoding result will go. The limit is set to one past the position of the final char.

Throws:

IllegalArgumentException - If either the input or the output buffer is not backed by an array

encode

public static void encode(byte[] inputArray,
          int inputOffset,
          int inputLength,
          char[] outputArray,
          int outputOffset,
          int outputLength)

Encodes the input byte sequence into the output char sequence. Before calling this method, ensure that the output array has sufficient capacity by calling getEncodedLength(byte[], int, int).

Parameters:

inputArray - byte sequence to be encoded

inputOffset - initial offset into inputArray

inputLength - number of bytes in inputArray

outputArray - char sequence to store encoded result

outputOffset - initial offset into outputArray

outputLength - length of output, must be getEncodedLength

decode

@Deprecated
public static void decode(CharBuffer input,
                     ByteBuffer output)

Deprecated. Use decode(char[], int, int, byte[], int, int) instead. This method will be removed in Lucene 4.0

Decodes the input char sequence into the output byte sequence. Before calling this method, ensure that the output ByteBuffer has sufficient capacity by calling getDecodedLength(java.nio.CharBuffer).

Parameters:

input - The char sequence to decode

output - Where the byte sequence decoding result will go. The limit is set to one past the position of the final char.

Throws:

IllegalArgumentException - If either the input or the output buffer is not backed by an array

decode

public static void decode(char[] inputArray,
          int inputOffset,
          int inputLength,
          byte[] outputArray,
          int outputOffset,
          int outputLength)

Decodes the input char sequence into the output byte sequence. Before calling this method, ensure that the output array has sufficient capacity by calling getDecodedLength(char[], int, int).

Parameters:

inputArray - char sequence to be decoded

inputOffset - initial offset into inputArray

inputLength - number of chars in inputArray

outputArray - byte sequence to store encoded result

outputOffset - initial offset into outputArray

outputLength - length of output, must be getDecodedLength(inputArray, inputOffset, inputLength)

decode

@Deprecated
public static ByteBuffer decode(CharBuffer input)

Deprecated. Use decode(char[], int, int, byte[], int, int) instead. This method will be removed in Lucene 4.0

Decodes the given char sequence, which must have been encoded by encode(java.nio.ByteBuffer) or encode(java.nio.ByteBuffer, java.nio.CharBuffer).

Parameters:

input - The char sequence to decode

Returns:

A byte sequence containing the decoding result. The limit is set to one past the position of the final char.

Throws:

IllegalArgumentException - If the input buffer is not backed by an array

encode

@Deprecated
public static CharBuffer encode(ByteBuffer input)

Deprecated. Use encode(byte[], int, int, char[], int, int) instead. This method will be removed in Lucene 4.0

Encodes the input byte sequence.

Parameters:

input - The byte sequence to encode

Returns:

A char sequence containing the encoding result. The limit is set to one past the position of the final char.

Throws:

IllegalArgumentException - If the input buffer is not backed by an array