+ * 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 + */ +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; + } + 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() { + } +}