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CollationKey Class Reference
Collation keys are generated by the Collator class.
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#include <sortkey.h>
List of all members.
Detailed Description
Collation keys are generated by the Collator class.
Use the CollationKey objects instead of Collator to compare strings multiple times. A CollationKey preprocesses the comparison information from the Collator object to make the comparison faster. If you are not going to comparing strings multiple times, then using the Collator object is generally faster, since it only processes as much of the string as needed to make a comparison.
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 );
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: Collator
s 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.
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See also:
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Collator , RuleBasedCollator
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Version:
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1.3 12/18/96
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Author(s):
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Helena Shih
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Deprecated:
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Definition at line 86 of file sortkey.h.
Constructor & Destructor Documentation
CollationKey::CollationKey (
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)
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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. -
Deprecated:
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Creates a collation key based on the collation key values.
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Parameters:
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values
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the collation key values |
count
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number of collation key values, including trailing nulls. |
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See also:
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createBits
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Deprecated:
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CollationKey::CollationKey (
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const CollationKey & other )
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Copy constructor.
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Deprecated:
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CollationKey::~CollationKey (
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)
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Sort key destructor.
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Deprecated:
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CollationKey::CollationKey (
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int32_t count,
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uint8_t * values ) [private]
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The secret adopting constructor!
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CollationKey::CollationKey (
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const UnicodeString & value ) [private]
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Member Function Documentation
void CollationKey::adopt (
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uint8_t * values,
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int32_t count ) [private]
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Convenience method which does a string(bit-wise) comparison of the two collation keys.
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Parameters:
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sourceKey
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source collation key |
targetKey
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target collation key |
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Returns:
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Returns Collator::LESS if sourceKey < targetKey, Collator::GREATER if sourceKey > targetKey and Collator::EQUAL otherwise.
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Deprecated:
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CollationKey& CollationKey::copyUnicodeString (
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const UnicodeString & value ) [private]
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Returns an array of the collation key values as 16-bit integers.
The caller owns the storage and must delete it. -
Parameters:
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size
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output parameter of the number of collation key values |
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Returns:
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a pointer to an array of 16-bit collation key values.
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CollationKey& CollationKey::ensureCapacity (
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int32_t newSize ) [private]
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const uint8_t * CollationKey::getByteArray (
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int32_t & count ) const [inline]
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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. -
Parameters:
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count
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the output parameter of number of collation key values, including any trailing nulls. |
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Deprecated:
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Definition at line 257 of file sortkey.h. |
int32_t CollationKey::hashCode (
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void ) const
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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()
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Returns:
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the hash value based on the string's collation order.
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See also:
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UnicodeString::hashCode
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Deprecated:
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UBool CollationKey::isBogus (
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void ) const [inline]
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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. -
Returns:
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Returns TRUE if the key is in an invalid, FALSE otherwise.
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Deprecated:
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Definition at line 251 of file sortkey.h. |
UBool CollationKey::operator!= (
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const CollationKey & other ) const [inline]
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Compare if two collation keys are not the same.
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Parameters:
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source
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the collation key to compare to. |
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Returns:
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Returns TRUE if two collation keys are different, FALSE otherwise.
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Deprecated:
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Definition at line 245 of file sortkey.h. |
const CollationKey & CollationKey::operator= (
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const CollationKey & other )
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Assignment operator.
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Deprecated:
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UBool CollationKey::operator== (
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const CollationKey & source ) const
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Compare if two collation keys are the same.
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Parameters:
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source
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the collation key to compare to. |
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Returns:
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Returns true if two collation keys are equal, false otherwise.
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Deprecated:
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CollationKey& CollationKey::reset (
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void ) [private]
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void CollationKey::reverseBytes (
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int32_t from,
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int32_t to ) [private]
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CollationKey& CollationKey::setToBogus (
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void ) [private]
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Extracts the collation key values into a new array.
The caller owns this storage and should free it. -
Parameters:
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count
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the output parameter of number of collation key values, including any trailing nulls. |
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Deprecated:
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Friends And Related Function Documentation
class RuleBasedCollator [friend]
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Member Data Documentation
UBool CollationKey::fBogus [private]
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uint8_t * CollationKey::fBytes [private]
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int32_t CollationKey::fCapacity [private]
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int32_t CollationKey::fCount [private]
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int32_t CollationKey::fHashCode [private]
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const int32_t CollationKey::kEmptyHashCode [static, private]
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const int32_t CollationKey::kInvalidHashCode [static, private]
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The documentation for this class was generated from the following file:
Generated at Tue Jun 12 14:04:25 2001 for ICU 1.8.1 by
1.2.3 written by Dimitri van Heesch,
© 1997-2000