* 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 * Unicode Standard Annex #15: * Unicode Normalization Forms. 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() { } }