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: *
* . 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;
* . }
* . //...
*
* 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 */ class U_I18N_API CollationKey { 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. */ 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. * @see #createBits */ CollationKey(const uint8_t* values, int32_t count); /** * Copy constructor. */ CollationKey(const CollationKey& other); /** * Sort key destructor. */ ~CollationKey(); /** * Assignment operator */ 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. */ bool_t 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. */ bool_t 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. */ bool_t 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. */ const uint8_t* getByteArray(int32_t& count) const; /** * 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. */ uint8_t* toByteArray(int32_t& count) const; /** * Convenience method which does a string(bit-wise) comparison of the * two collation keys. * @param sourceKey source collation key * @param targetKey target collation key * @return Returns Collator::LESS if sourceKey < targetKey, * Collator::GREATER if sourceKey > targetKey and Collator::EQUAL * otherwise. */ Collator::EComparisonResult compareTo(const CollationKey& target) 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
*/
int32_t hashCode(void) const;
private:
/**
* Returns an array of the collation key values as 16-bit integers.
* The caller owns the storage and must delete it.
* @param size output parameter of the number of collation key values
* @return a pointer to an array of 16-bit collation key values.
*/
uint16_t* copyValues(int32_t &size) const;
/*
* Creates a collation key with a string.
*/
CollationKey(const UnicodeString& value);
int32_t storeBytes(int32_t cursor, uint32_t byteValue);
int32_t storeUnicodeString(int32_t cursor, const UnicodeString &value);
void reverseBytes(int32_t from, int32_t to);
CollationKey& ensureCapacity(int32_t newSize);
CollationKey& copyUnicodeString(const UnicodeString &value);
CollationKey& setToBogus(void);
CollationKey& reset(void);
friend class RuleBasedCollator;
static const int32_t kInvalidHashCode;
static const int32_t kEmptyHashCode;
bool_t fBogus;
int32_t fCount;
int32_t fCapacity;
int32_t fHashCode;
uint8_t* fBytes;
};
inline bool_t
CollationKey::operator!=(const CollationKey& other) const
{
return !(*this == other);
}
inline bool_t
CollationKey::isBogus() const
{
return fBogus;
}
inline const uint8_t*
CollationKey::getByteArray(int32_t &count) const
{
count = fCount;
return fBytes;
}
inline UTextOffset
CollationKey::storeBytes(UTextOffset cursor, uint32_t byteValue)
{
fBytes[cursor++] = (uint8_t) (byteValue >> 8);
fBytes[cursor++] = (uint8_t) byteValue;
return cursor;
}
#endif