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CollationKey Class Reference

Collation keys are generated by the Collator class. More...

#include <sortkey.h>

List of all members.

Public Methods

 CollationKey ()
 This creates an empty collation key based on the null string. More...

 CollationKey (const uint8_t *values, int32_t count)
 Creates a collation key based on the collation key values. More...

 CollationKey (const CollationKey &other)
 Copy constructor. More...

 ~CollationKey ()
 Sort key destructor. More...

const CollationKey & operator= (const CollationKey &other)
 Assignment operator. More...

UBool operator== (const CollationKey &source) const
 Compare if two collation keys are the same. More...

UBool operator!= (const CollationKey &source) const
 Compare if two collation keys are not the same. More...

UBool isBogus (void) const
 Test to see if the key is in an invalid state. More...

const uint8_tgetByteArray (int32_t &count) const
 Returns a pointer to the collation key values. More...

uint8_ttoByteArray (int32_t &count) const
 Extracts the collation key values into a new array. More...

Collator::EComparisonResult compareTo (const CollationKey &target) const
 Convenience method which does a string(bit-wise) comparison of the two collation keys. More...

int32_t hashCode (void) const
 Creates an integer that is unique to the collation key. More...


Private Methods

void adopt (uint8_t *values, int32_t count)
 Returns an array of the collation key values as 16-bit integers. More...

CollationKey & ensureCapacity (int32_t newSize)
CollationKey & setToBogus (void)
CollationKey & reset (void)

Private Attributes

UBool fBogus
int32_t fCount
int32_t fCapacity
int32_t fHashCode
uint8_tfBytes

Friends

class RuleBasedCollator


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 );

     // 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 also:
Collator , RuleBasedCollator
Version:
1.3 12/18/96
Author:
Helena Shih

Definition at line 87 of file sortkey.h.


Constructor & Destructor Documentation

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.

Stable:

CollationKey::CollationKey const uint8_t   values,
int32_t    count
 

Creates a collation key based on the collation key values.

Parameters:
values  the collation key values
count  number of collation key values, including trailing nulls.
See also:
createBits
Stable:

CollationKey::CollationKey const CollationKey &    other
 

Copy constructor.

Stable:

CollationKey::~CollationKey  
 

Sort key destructor.

Stable:


Member Function Documentation

void CollationKey::adopt uint8_t   values,
int32_t    count
[private]
 

Returns an array of the collation key values as 16-bit integers.

The caller owns the storage and must delete it.

Parameters:
size  output parameter of the number of collation key values
Returns:
a pointer to an array of 16-bit collation key values.

Collator::EComparisonResult CollationKey::compareTo const CollationKey &    target const
 

Convenience method which does a string(bit-wise) comparison of the two collation keys.

Parameters:
sourceKey  source collation key
targetKey  target collation key
Returns:
Returns Collator::LESS if sourceKey < targetKey, Collator::GREATER if sourceKey > targetKey and Collator::EQUAL otherwise.
Stable:

CollationKey& CollationKey::ensureCapacity int32_t    newSize [private]
 

const uint8_t * CollationKey::getByteArray int32_t   count const [inline]
 

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:
count  the output parameter of number of collation key values, including any trailing nulls.
Stable:

Definition at line 243 of file sortkey.h.

int32_t CollationKey::hashCode void    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()
 
Returns:
the hash value based on the string's collation order.
See also:
UnicodeString::hashCode
Stable:

UBool CollationKey::isBogus void    const [inline]
 

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:
Returns TRUE if the key is in an invalid, FALSE otherwise.
Stable:

Definition at line 237 of file sortkey.h.

UBool CollationKey::operator!= const CollationKey &    other const [inline]
 

Compare if two collation keys are not the same.

Parameters:
source  the collation key to compare to.
Returns:
Returns TRUE if two collation keys are different, FALSE otherwise.
Stable:

Definition at line 231 of file sortkey.h.

const CollationKey& CollationKey::operator= const CollationKey &    other
 

Assignment operator.

Stable:

UBool CollationKey::operator== const CollationKey &    source const
 

Compare if two collation keys are the same.

Parameters:
source  the collation key to compare to.
Returns:
Returns true if two collation keys are equal, false otherwise.
Stable:

CollationKey& CollationKey::reset void    [private]
 

CollationKey& CollationKey::setToBogus void    [private]
 

uint8_t* CollationKey::toByteArray int32_t   count const
 

Extracts the collation key values into a new array.

The caller owns this storage and should free it.

Parameters:
count  the output parameter of number of collation key values, including any trailing nulls.
Deprecated:
Remove after 2003-mar-25. Use getByteArray instead.


Friends And Related Function Documentation

friend class RuleBasedCollator [friend]
 

Definition at line 221 of file sortkey.h.


Member Data Documentation

UBool CollationKey::fBogus [private]
 

Definition at line 223 of file sortkey.h.

uint8_t* CollationKey::fBytes [private]
 

Definition at line 227 of file sortkey.h.

int32_t CollationKey::fCapacity [private]
 

Definition at line 225 of file sortkey.h.

int32_t CollationKey::fCount [private]
 

Definition at line 224 of file sortkey.h.

int32_t CollationKey::fHashCode [private]
 

Definition at line 226 of file sortkey.h.


The documentation for this class was generated from the following file:
Generated on Tue Apr 9 11:30:31 2002 for ICU 2.1 by doxygen1.2.11.1 written by Dimitri van Heesch, © 1997-2001