* The primary functions are to produce a normalized string and to detect whether * a string is already normalized. * The most commonly used normalization forms are those defined in * http://www.unicode.org/unicode/reports/tr15/ * However, this API supports additional normalization forms for specialized purposes. * For example, NFKC_Casefold is provided via getInstance("nfkc_cf", COMPOSE) * and can be used in implementations of UTS #46. *
* Not only are the standard compose and decompose modes supplied, * but additional modes are provided as documented in the Mode enum. *
* Some of the functions in this class identify normalization boundaries. * At a normalization boundary, the portions of the string * before it and starting from it do not interact and can be handled independently. *
* The spanQuickCheckYes() stops at a normalization boundary. * When the goal is a normalized string, then the text before the boundary * can be copied, and the remainder can be processed with normalizeSecondAndAppend(). *
* The hasBoundaryBefore(), hasBoundaryAfter() and isInert() functions test whether * a character is guaranteed to be at a normalization boundary, * regardless of context. * This is used for moving from one normalization boundary to the next * or preceding boundary, and for performing iterative normalization. *
* Iterative normalization is useful when only a small portion of a * longer string needs to be processed. * For example, in ICU, iterative normalization is used by the NormalizationTransliterator * (to avoid replacing already-normalized text) and ucol_nextSortKeyPart() * (to process only the substring for which sort key bytes are computed). *
* The set of normalization boundaries returned by these functions may not be * complete: There may be more boundaries that could be returned. * Different functions may return different boundaries. * @stable ICU 4.4 * @author Markus W. Scherer */ public abstract class Normalizer2 { /** * Returns a Normalizer2 instance for Unicode NFC normalization. * Same as getInstance(null, "nfc", Mode.COMPOSE). * Returns an unmodifiable singleton instance. * @return the requested Normalizer2, if successful * @stable ICU 49 */ public static Normalizer2 getNFCInstance() { return Norm2AllModes.getNFCInstance().comp; } /** * Returns a Normalizer2 instance for Unicode NFD normalization. * Same as getInstance(null, "nfc", Mode.DECOMPOSE). * Returns an unmodifiable singleton instance. * @return the requested Normalizer2, if successful * @stable ICU 49 */ public static Normalizer2 getNFDInstance() { return Norm2AllModes.getNFCInstance().decomp; } /** * Returns a Normalizer2 instance for Unicode NFKC normalization. * Same as getInstance(null, "nfkc", Mode.COMPOSE). * Returns an unmodifiable singleton instance. * @return the requested Normalizer2, if successful * @stable ICU 49 */ public static Normalizer2 getNFKCInstance() { return Norm2AllModes.getNFKCInstance().comp; } /** * Returns a Normalizer2 instance for Unicode NFKD normalization. * Same as getInstance(null, "nfkc", Mode.DECOMPOSE). * Returns an unmodifiable singleton instance. * @return the requested Normalizer2, if successful * @stable ICU 49 */ public static Normalizer2 getNFKDInstance() { return Norm2AllModes.getNFKCInstance().decomp; } /** * Returns the normalized form of the source string. * @param src source string * @return normalized src * @stable ICU 4.4 */ public String normalize(CharSequence src) { if(src instanceof String) { // Fastpath: Do not construct a new String if the src is a String // and is already normalized. int spanLength=spanQuickCheckYes(src); if(spanLength==src.length()) { return (String)src; } if (spanLength != 0) { StringBuilder sb=new StringBuilder(src.length()).append(src, 0, spanLength); return normalizeSecondAndAppend(sb, src.subSequence(spanLength, src.length())).toString(); } } return normalize(src, new StringBuilder(src.length())).toString(); } /** * Writes the normalized form of the source string to the destination string * (replacing its contents) and returns the destination string. * The source and destination strings must be different objects. * @param src source string * @param dest destination string; its contents is replaced with normalized src * @return dest * @stable ICU 4.4 */ public abstract StringBuilder normalize(CharSequence src, StringBuilder dest); /** * Writes the normalized form of the source string to the destination Appendable * and returns the destination Appendable. * The source and destination strings must be different objects. * *
Any {@link java.io.IOException} is wrapped into a {@link com.ibm.icu.util.ICUUncheckedIOException}.
*
* @param src source string
* @param dest destination Appendable; gets normalized src appended
* @return dest
* @stable ICU 4.6
*/
public abstract Appendable normalize(CharSequence src, Appendable dest);
/**
* Appends the normalized form of the second string to the first string
* (merging them at the boundary) and returns the first string.
* The result is normalized if the first string was normalized.
* The first and second strings must be different objects.
* @param first string, should be normalized
* @param second string, will be normalized
* @return first
* @stable ICU 4.4
*/
public abstract StringBuilder normalizeSecondAndAppend(
StringBuilder first, CharSequence second);
/**
* Appends the second string to the first string
* (merging them at the boundary) and returns the first string.
* The result is normalized if both the strings were normalized.
* The first and second strings must be different objects.
* @param first string, should be normalized
* @param second string, should be normalized
* @return first
* @stable ICU 4.4
*/
public abstract StringBuilder append(StringBuilder first, CharSequence second);
/**
* Gets the decomposition mapping of c.
* Roughly equivalent to normalizing the String form of c
* on a DECOMPOSE Normalizer2 instance, but much faster, and except that this function
* returns null if c does not have a decomposition mapping in this instance's data.
* This function is independent of the mode of the Normalizer2.
* @param c code point
* @return c's decomposition mapping, if any; otherwise null
* @stable ICU 4.6
*/
public abstract String getDecomposition(int c);
/**
* Gets the combining class of c.
* The default implementation returns 0
* but all standard implementations return the Unicode Canonical_Combining_Class value.
* @param c code point
* @return c's combining class
* @stable ICU 49
*/
public int getCombiningClass(int c) { return 0; }
/**
* Tests if the string is normalized.
* Internally, in cases where the quickCheck() method would return "maybe"
* (which is only possible for the two COMPOSE modes) this method
* resolves to "yes" or "no" to provide a definitive result,
* at the cost of doing more work in those cases.
* @param s input string
* @return true if s is normalized
* @stable ICU 4.4
*/
public abstract boolean isNormalized(CharSequence s);
/**
* Returns the end of the normalized substring of the input string.
* In other words, with end=spanQuickCheckYes(s);
* the substring s.subSequence(0, end)
* will pass the quick check with a "yes" result.
*
* The returned end index is usually one or more characters before the * "no" or "maybe" character: The end index is at a normalization boundary. * (See the class documentation for more about normalization boundaries.) *
* When the goal is a normalized string and most input strings are expected * to be normalized already, then call this method, * and if it returns a prefix shorter than the input string, * copy that prefix and use normalizeSecondAndAppend() for the remainder. * @param s input string * @return "yes" span end index * @stable ICU 4.4 */ public abstract int spanQuickCheckYes(CharSequence s); /** * Tests if the character always has a normalization boundary before it, * regardless of context. * If true, then the character does not normalization-interact with * preceding characters. * In other words, a string containing this character can be normalized * by processing portions before this character and starting from this * character independently. * This is used for iterative normalization. See the class documentation for details. * @param c character to test * @return true if c has a normalization boundary before it * @stable ICU 4.4 */ public abstract boolean hasBoundaryBefore(int c); /** * Sole constructor. (For invocation by subclass constructors, * typically implicit.) * @internal * deprecated This API is ICU internal only. */ protected Normalizer2() { } }