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