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java.lang.Object org.apache.lucene.util.IndexableBinaryStringTools
public class IndexableBinaryStringTools
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.
Method Summary | |
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static ByteBuffer |
decode(CharBuffer input)
Decodes the given char sequence, which must have been encoded by encode(java.nio.ByteBuffer) or
encode(java.nio.ByteBuffer, java.nio.CharBuffer) . |
static void |
decode(CharBuffer input,
ByteBuffer output)
Decodes the input char sequence into the output byte sequence. |
static CharBuffer |
encode(ByteBuffer input)
Encodes the input byte sequence. |
static void |
encode(ByteBuffer input,
CharBuffer output)
Encodes the input byte sequence into the output char sequence. |
static int |
getDecodedLength(CharBuffer encoded)
Returns the number of bytes required to decode the given char sequence. |
static int |
getEncodedLength(ByteBuffer original)
Returns the number of chars required to encode the given byte sequence. |
Methods inherited from class java.lang.Object |
---|
clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait |
Method Detail |
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public static int getEncodedLength(ByteBuffer original) throws IllegalArgumentException
original
- The byte sequence to be encoded. Must be backed by an array.
IllegalArgumentException
- If the given ByteBuffer is not backed by an arraypublic static int getDecodedLength(CharBuffer encoded) throws IllegalArgumentException
encoded
- The char sequence to be encoded. Must be backed by an array.
IllegalArgumentException
- If the given CharBuffer is not backed by an arraypublic static void encode(ByteBuffer input, CharBuffer output)
getEncodedLength(java.nio.ByteBuffer)
.
input
- The byte sequence to encodeoutput
- Where the char sequence encoding result will go. The limit
is set to one past the position of the final char.
IllegalArgumentException
- If either the input or the output buffer
is not backed by an arraypublic static void decode(CharBuffer input, ByteBuffer output)
getDecodedLength(java.nio.CharBuffer)
.
input
- The char sequence to decodeoutput
- Where the byte sequence decoding result will go. The limit
is set to one past the position of the final char.
IllegalArgumentException
- If either the input or the output buffer
is not backed by an arraypublic static ByteBuffer decode(CharBuffer input)
encode(java.nio.ByteBuffer)
or
encode(java.nio.ByteBuffer, java.nio.CharBuffer)
.
input
- The char sequence to decode
IllegalArgumentException
- If the input buffer is not backed by an
arraypublic static CharBuffer encode(ByteBuffer input)
input
- The byte sequence to encode
IllegalArgumentException
- If the input buffer is not backed by an
array
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