org.apache.lucene.util

Class StringHelper

java.lang.Object

org.apache.lucene.util.StringHelper

public abstract class StringHelper
extends Object

Methods for manipulating strings.

NOTE: This API is for internal purposes only and might change in incompatible ways in the next release.

Field Summary

Fields

Modifier and Type	Field and Description
static int	GOOD_FAST_HASH_SEED Pass this as the seed to murmurhash3_x86_32(byte[], int, int, int).
static int	ID_LENGTH length in bytes of an ID

Method Summary

Modifier and Type	Method and Description
static int	bytesDifference(BytesRef left, BytesRef right) Compares two BytesRef, element by element, and returns the number of elements common to both arrays (from the start of each).
static int	compare(int count, byte[] a, int aOffset, byte[] b, int bOffset) Compares a fixed length slice of two byte arrays interpreted as big-endian unsigned values.
static boolean	endsWith(BytesRef ref, BytesRef suffix) Returns true iff the ref ends with the given suffix.
static String	idToString(byte[] id) Helper method to render an ID as a string, for debugging
static BytesRef	intsRefToBytesRef(IntsRef ints) Just converts each int in the incoming IntsRef to each byte in the returned BytesRef, throwing IllegalArgumentException if any int value is out of bounds for a byte.
static int	murmurhash3_x86_32(byte[] data, int offset, int len, int seed) Returns the MurmurHash3_x86_32 hash.
static int	murmurhash3_x86_32(BytesRef bytes, int seed)
static byte[]	randomId() Generates a non-cryptographic globally unique id.
static int	sortKeyLength(BytesRef priorTerm, BytesRef currentTerm) Returns the length of currentTerm needed for use as a sort key.
static boolean	startsWith(byte[] ref, BytesRef prefix) Returns true iff the ref starts with the given prefix.
static boolean	startsWith(BytesRef ref, BytesRef prefix) Returns true iff the ref starts with the given prefix.

Methods inherited from class java.lang.Object

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

Field Detail

GOOD_FAST_HASH_SEED

public static final int GOOD_FAST_HASH_SEED

Pass this as the seed to murmurhash3_x86_32(byte[], int, int, int).

ID_LENGTH

public static final int ID_LENGTH

length in bytes of an ID

See Also:

Constant Field Values

Method Detail

bytesDifference

public static int bytesDifference(BytesRef left,
                                  BytesRef right)

Compares two BytesRef, element by element, and returns the number of elements common to both arrays (from the start of each).

Parameters:

left - The first BytesRef to compare

right - The second BytesRef to compare

Returns:

The number of common elements (from the start of each).

sortKeyLength

public static int sortKeyLength(BytesRef priorTerm,
                                BytesRef currentTerm)

Returns the length of currentTerm needed for use as a sort key. so that BytesRef.compareTo(BytesRef) still returns the same result. This method assumes currentTerm comes after priorTerm.

startsWith

public static boolean startsWith(byte[] ref,
                                 BytesRef prefix)

Returns true iff the ref starts with the given prefix. Otherwise false.

Parameters:

ref - the byte[] to test

prefix - the expected prefix

Returns:

Returns true iff the ref starts with the given prefix. Otherwise false.

startsWith

public static boolean startsWith(BytesRef ref,
                                 BytesRef prefix)

Returns true iff the ref starts with the given prefix. Otherwise false.

Parameters:

ref - the BytesRef to test

prefix - the expected prefix

Returns:

Returns true iff the ref starts with the given prefix. Otherwise false.

endsWith

public static boolean endsWith(BytesRef ref,
                               BytesRef suffix)

Returns true iff the ref ends with the given suffix. Otherwise false.

Parameters:

ref - the BytesRef to test

suffix - the expected suffix

Returns:

Returns true iff the ref ends with the given suffix. Otherwise false.

murmurhash3_x86_32

public static int murmurhash3_x86_32(byte[] data,
                                     int offset,
                                     int len,
                                     int seed)

Returns the MurmurHash3_x86_32 hash. Original source/tests at https://github.com/yonik/java_util/

murmurhash3_x86_32

public static int murmurhash3_x86_32(BytesRef bytes,
                                     int seed)

randomId

public static byte[] randomId()

Generates a non-cryptographic globally unique id.

idToString

public static String idToString(byte[] id)

Helper method to render an ID as a string, for debugging

Returns the string (null) if the id is null. Otherwise, returns a string representation for debugging. Never throws an exception. The returned string may indicate if the id is definitely invalid.

intsRefToBytesRef

public static BytesRef intsRefToBytesRef(IntsRef ints)

Just converts each int in the incoming IntsRef to each byte in the returned BytesRef, throwing IllegalArgumentException if any int value is out of bounds for a byte.

compare

public static int compare(int count,
                          byte[] a,
                          int aOffset,
                          byte[] b,
                          int bOffset)

Compares a fixed length slice of two byte arrays interpreted as big-endian unsigned values. Returns positive int if a > b, negative int if a < b and 0 if a == b