ICU 75.1 75.1
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Collation keys are generated by the Collator class. More...
#include <sortkey.h>
Public Member Functions | |
CollationKey () | |
This creates an empty collation key based on the null string. | |
CollationKey (const uint8_t *values, int32_t count) | |
Creates a collation key based on the collation key values. | |
CollationKey (const CollationKey &other) | |
Copy constructor. | |
virtual | ~CollationKey () |
Sort key destructor. | |
const CollationKey & | operator= (const CollationKey &other) |
Assignment operator. | |
bool | operator== (const CollationKey &source) const |
Compare if two collation keys are the same. | |
bool | operator!= (const CollationKey &source) const |
Compare if two collation keys are not the same. | |
UBool | isBogus () const |
Test to see if the key is in an invalid state. | |
const uint8_t * | getByteArray (int32_t &count) const |
Returns a pointer to the collation key values. | |
Collator::EComparisonResult | compareTo (const CollationKey &target) const |
Convenience method which does a string(bit-wise) comparison of the two collation keys. | |
UCollationResult | compareTo (const CollationKey &target, UErrorCode &status) const |
Convenience method which does a string(bit-wise) comparison of the two collation keys. | |
int32_t | hashCode () const |
Creates an integer that is unique to the collation key. | |
virtual UClassID | getDynamicClassID () const override |
ICU "poor man's RTTI", returns a UClassID for the actual class. | |
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virtual | ~UObject () |
Destructor. | |
Static Public Member Functions | |
static UClassID | getStaticClassID () |
ICU "poor man's RTTI", returns a UClassID for this class. | |
Friends | |
class | RuleBasedCollator |
Allow private access to RuleBasedCollator. | |
class | CollationKeyByteSink |
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:
// Inside body of sort routine, compare keys this way:if(keys[0].compareTo( keys[1] ) > 0 ) {}//...Collator::EComparisonResult compareTo(const CollationKey &target) constConvenience method which does a string(bit-wise) comparison of the two collation keys.static Collator * createInstance(UErrorCode &err)Creates the Collator object for the current default locale."Smart pointer" base class; do not use directly: use LocalPointer etc.Definition localpointer.h:68
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.
icu::CollationKey::CollationKey | ( | ) |
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.
Creates a collation key based on the collation key values.
values | the collation key values |
count | number of collation key values, including trailing nulls. |
icu::CollationKey::CollationKey | ( | const CollationKey & | other | ) |
Collator::EComparisonResult icu::CollationKey::compareTo | ( | const CollationKey & | target | ) | const |
Convenience method which does a string(bit-wise) comparison of the two collation keys.
target | target collation key to be compared with |
UCollationResult icu::CollationKey::compareTo | ( | const CollationKey & | target, |
UErrorCode & | status | ||
) | const |
Convenience method which does a string(bit-wise) comparison of the two collation keys.
target | target collation key to be compared with |
status | error code |
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.
count | the output parameter of number of collation key values, including any trailing nulls. |
ICU "poor man's RTTI", returns a UClassID for the actual class.
Reimplemented from icu::UObject.
ICU "poor man's RTTI", returns a UClassID for this class.
int32_t icu::CollationKey::hashCode | ( | ) | 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()
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const CollationKey & icu::CollationKey::operator= | ( | const CollationKey & | other | ) |
bool icu::CollationKey::operator== | ( | const CollationKey & | source | ) | const |
Compare if two collation keys are the same.
source | the collation key to compare to. |
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friend |
Allow private access to RuleBasedCollator.