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 */ bool 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 */ bool 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 override;
/**
* 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 nullptr 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 bool
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 /* U_SHOW_CPLUSPLUS_API */
#endif