Save This Page
Home » lucene-3.0.1-src » org.apache » lucene » util » [javadoc | source]
public class: IndexableBinaryStringTools [javadoc | source]
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. This class's operations are defined over CharBuffers and ByteBuffers, to allow for wrapped arrays to be reused, reducing memory allocation costs for repeated operations. 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.
Nested Class Summary:
static class  IndexableBinaryStringTools.CodingCase   
Method from org.apache.lucene.util.IndexableBinaryStringTools Summary:
decode,   decode,   encode,   encode,   getDecodedLength,   getEncodedLength
Methods from java.lang.Object:
clone,   equals,   finalize,   getClass,   hashCode,   notify,   notifyAll,   toString,   wait,   wait,   wait
Method from org.apache.lucene.util.IndexableBinaryStringTools Detail:
 public static ByteBuffer decode(CharBuffer input) 
 public static  void decode(CharBuffer input,
    ByteBuffer output) 
    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) .
 public static CharBuffer encode(ByteBuffer input) 
    Encodes the input byte sequence.
 public static  void encode(ByteBuffer input,
    CharBuffer output) 
    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) .
 public static int getDecodedLength(CharBuffer encoded) throws IllegalArgumentException 
    Returns the number of bytes required to decode the given char sequence.
 public static int getEncodedLength(ByteBuffer original) throws IllegalArgumentException 
    Returns the number of chars required to encode the given byte sequence.