For example (with strength == tertiary) + *
When comparing "Abernathy" to "Baggins-Smythworthy", Collator + * only needs to process a couple of characters, while a comparison + * with CollationKeys will process all of the characters. On the other hand, + * if you are doing a sort of a number of fields, it is much faster to use + * CollationKeys, since you will be comparing strings multiple times. + *
Typical use of CollationKeys are in databases, where you store a CollationKey + * in a hidden field, and use it for sorting or indexing. + * + *
Example of use: + *
+ * \code
+ * UErrorCode success = U_ZERO_ERROR;
+ * Collator* myCollator = Collator::createInstance(success);
+ * CollationKey* keys = new CollationKey [3];
+ * myCollator->getCollationKey("Tom", keys[0], success );
+ * myCollator->getCollationKey("Dick", keys[1], success );
+ * myCollator->getCollationKey("Harry", keys[2], success );
+ *
+ * // Inside body of sort routine, compare keys this way:
+ * CollationKey tmp;
+ * if(keys[0].compareTo( keys[1] ) > 0 ) {
+ * tmp = keys[0]; keys[0] = keys[1]; keys[1] = tmp;
+ * }
+ * //...
+ * \endcode
+ *
+ * Because Collator::compare()'s algorithm is complex, it is faster to sort + * long lists of words by retrieving collation keys with Collator::getCollationKey(). + * You can then cache the collation keys and compare them using CollationKey::compareTo(). + *
+ * Note: Collators with different Locale,
+ * CollationStrength and DecompositionMode settings will return different
+ * CollationKeys for the same set of strings. Locales have specific
+ * collation rules, and the way in which secondary and tertiary differences
+ * are taken into account, for example, will result in different CollationKeys
+ * for same strings.
+ *
+ + * @see Collator + * @see RuleBasedCollator + * @version 1.3 12/18/96 + * @author Helena Shih + * @stable ICU 2.0 + */ +class U_I18N_API CollationKey : public UObject { +public: + /** + * This creates an empty collation key based on the null string. An empty + * collation key contains no sorting information. When comparing two empty + * collation keys, the result is Collator::EQUAL. Comparing empty collation key + * with non-empty collation key is always Collator::LESS. + * @stable ICU 2.0 + */ + CollationKey(); + + + /** + * Creates a collation key based on the collation key values. + * @param values the collation key values + * @param count number of collation key values, including trailing nulls. + * @stable ICU 2.0 + */ + CollationKey(const uint8_t* values, + int32_t count); + + /** + * Copy constructor. + * @param other the object to be copied. + * @stable ICU 2.0 + */ + CollationKey(const CollationKey& other); + + /** + * Sort key destructor. + * @stable ICU 2.0 + */ + virtual ~CollationKey(); + + /** + * Assignment operator + * @param other the object to be copied. + * @stable ICU 2.0 + */ + const CollationKey& operator=(const CollationKey& other); + + /** + * Compare if two collation keys are the same. + * @param source the collation key to compare to. + * @return Returns true if two collation keys are equal, false otherwise. + * @stable ICU 2.0 + */ + UBool operator==(const CollationKey& source) const; + + /** + * Compare if two collation keys are not the same. + * @param source the collation key to compare to. + * @return Returns TRUE if two collation keys are different, FALSE otherwise. + * @stable ICU 2.0 + */ + UBool operator!=(const CollationKey& source) const; + + + /** + * Test to see if the key is in an invalid state. The key will be in an + * invalid state if it couldn't allocate memory for some operation. + * @return Returns TRUE if the key is in an invalid, FALSE otherwise. + * @stable ICU 2.0 + */ + UBool isBogus(void) const; + + /** + * Returns a pointer to the collation key values. The storage is owned + * by the collation key and the pointer will become invalid if the key + * is deleted. + * @param count the output parameter of number of collation key values, + * including any trailing nulls. + * @return a pointer to the collation key values. + * @stable ICU 2.0 + */ + const uint8_t* getByteArray(int32_t& count) const; + +#ifdef U_USE_COLLATION_KEY_DEPRECATES + /** + * Extracts the collation key values into a new array. The caller owns + * this storage and should free it. + * @param count the output parameter of number of collation key values, + * including any trailing nulls. + * @obsolete ICU 2.6. Use getByteArray instead since this API will be removed in that release. + */ + uint8_t* toByteArray(int32_t& count) const; +#endif + +#ifndef U_HIDE_DEPRECATED_API + /** + * Convenience method which does a string(bit-wise) comparison of the + * two collation keys. + * @param target target collation key to be compared with + * @return Returns Collator::LESS if sourceKey < targetKey, + * Collator::GREATER if sourceKey > targetKey and Collator::EQUAL + * otherwise. + * @deprecated ICU 2.6 use the overload with error code + */ + Collator::EComparisonResult compareTo(const CollationKey& target) const; +#endif /* U_HIDE_DEPRECATED_API */ + + /** + * Convenience method which does a string(bit-wise) comparison of the + * two collation keys. + * @param target target collation key to be compared with + * @param status error code + * @return Returns UCOL_LESS if sourceKey < targetKey, + * UCOL_GREATER if sourceKey > targetKey and UCOL_EQUAL + * otherwise. + * @stable ICU 2.6 + */ + UCollationResult compareTo(const CollationKey& target, UErrorCode &status) const; + + /** + * Creates an integer that is unique to the collation key. NOTE: this + * is not the same as String.hashCode. + *
Example of use: + *
+ * . UErrorCode status = U_ZERO_ERROR;
+ * . Collator *myCollation = Collator::createInstance(Locale::US, status);
+ * . if (U_FAILURE(status)) return;
+ * . CollationKey key1, key2;
+ * . UErrorCode status1 = U_ZERO_ERROR, status2 = U_ZERO_ERROR;
+ * . myCollation->getCollationKey("abc", key1, status1);
+ * . if (U_FAILURE(status1)) { delete myCollation; return; }
+ * . myCollation->getCollationKey("ABC", key2, status2);
+ * . if (U_FAILURE(status2)) { delete myCollation; return; }
+ * . // key1.hashCode() != key2.hashCode()
+ *
+ * @return the hash value based on the string's collation order.
+ * @see UnicodeString#hashCode
+ * @stable ICU 2.0
+ */
+ int32_t hashCode(void) const;
+
+ /**
+ * ICU "poor man's RTTI", returns a UClassID for the actual class.
+ * @stable ICU 2.2
+ */
+ virtual UClassID getDynamicClassID() const;
+
+ /**
+ * ICU "poor man's RTTI", returns a UClassID for this class.
+ * @stable ICU 2.2
+ */
+ static UClassID U_EXPORT2 getStaticClassID();
+
+private:
+ /**
+ * Replaces the current bytes buffer with a new one of newCapacity
+ * and copies length bytes from the old buffer to the new one.
+ * @return the new buffer, or NULL if the allocation failed
+ */
+ uint8_t *reallocate(int32_t newCapacity, int32_t length);
+ /**
+ * Set a new length for a new sort key in the existing fBytes.
+ */
+ void setLength(int32_t newLength);
+
+ uint8_t *getBytes() {
+ return (fFlagAndLength >= 0) ? fUnion.fStackBuffer : fUnion.fFields.fBytes;
+ }
+ const uint8_t *getBytes() const {
+ return (fFlagAndLength >= 0) ? fUnion.fStackBuffer : fUnion.fFields.fBytes;
+ }
+ int32_t getCapacity() const {
+ return (fFlagAndLength >= 0) ? (int32_t)sizeof(fUnion) : fUnion.fFields.fCapacity;
+ }
+ int32_t getLength() const { return fFlagAndLength & 0x7fffffff; }
+
+ /**
+ * Set the CollationKey to a "bogus" or invalid state
+ * @return this CollationKey
+ */
+ CollationKey& setToBogus(void);
+ /**
+ * Resets this CollationKey to an empty state
+ * @return this CollationKey
+ */
+ CollationKey& reset(void);
+
+ /**
+ * Allow private access to RuleBasedCollator
+ */
+ friend class RuleBasedCollator;
+ friend class CollationKeyByteSink;
+
+ // Class fields. sizeof(CollationKey) is intended to be 48 bytes
+ // on a machine with 64-bit pointers.
+ // We use a union to maximize the size of the internal buffer,
+ // similar to UnicodeString but not as tight and complex.
+
+ // (implicit) *vtable;
+ /**
+ * Sort key length and flag.
+ * Bit 31 is set if the buffer is heap-allocated.
+ * Bits 30..0 contain the sort key length.
+ */
+ int32_t fFlagAndLength;
+ /**
+ * Unique hash value of this CollationKey.
+ * Special value 2 if the key is bogus.
+ */
+ mutable int32_t fHashCode;
+ /**
+ * fUnion provides 32 bytes for the internal buffer or for
+ * pointer+capacity.
+ */
+ union StackBufferOrFields {
+ /** fStackBuffer is used iff fFlagAndLength>=0, else fFields is used */
+ uint8_t fStackBuffer[32];
+ struct {
+ uint8_t *fBytes;
+ int32_t fCapacity;
+ } fFields;
+ } fUnion;
+};
+
+inline UBool
+CollationKey::operator!=(const CollationKey& other) const
+{
+ return !(*this == other);
+}
+
+inline UBool
+CollationKey::isBogus() const
+{
+ return fHashCode == 2; // kBogusHashCode
+}
+
+inline const uint8_t*
+CollationKey::getByteArray(int32_t &count) const
+{
+ count = getLength();
+ return getBytes();
+}
+
+U_NAMESPACE_END
+
+#endif /* #if !UCONFIG_NO_COLLATION */
+
+#endif