icuSources/i18n/unicode/sortkey.h

   1 // © 2016 and later: Unicode, Inc. and others.
   2 // License & terms of use: http://www.unicode.org/copyright.html
   3 /*
   4  *****************************************************************************
   5  * Copyright (C) 1996-2014, International Business Machines Corporation and others.
   6  * All Rights Reserved.
   7  *****************************************************************************
   8  *
   9  * File sortkey.h
  10  *
  11  * Created by: Helena Shih
  12  *
  13  * Modification History:
  14  *
  15  *  Date         Name          Description
  16  *
  17  *  6/20/97     helena      Java class name change.
  18  *  8/18/97     helena      Added internal API documentation.
  19  *  6/26/98     erm         Changed to use byte arrays and memcmp.
  20  *****************************************************************************
  21  */
  22
  23 #ifndef SORTKEY_H
  24 #define SORTKEY_H
  25
  26 #include "unicode/utypes.h"
  27
  28 /**
  29  * \file
  30  * \brief C++ API: Keys for comparing strings multiple times.
  31  */
  32
  33 #if !UCONFIG_NO_COLLATION
  34
  35 #include "unicode/uobject.h"
  36 #include "unicode/unistr.h"
  37 #include "unicode/coll.h"
  38
  39 #if U_SHOW_CPLUSPLUS_API
  40 U_NAMESPACE_BEGIN
  41
  42 /* forward declaration */
  43 class RuleBasedCollator;
  44 class CollationKeyByteSink;
  45
  46 /**
  47  *
  48  * Collation keys are generated by the Collator class.  Use the CollationKey objects
  49  * instead of Collator to compare strings multiple times.  A CollationKey
  50  * preprocesses the comparison information from the Collator object to
  51  * make the comparison faster.  If you are not going to comparing strings
  52  * multiple times, then using the Collator object is generally faster,
  53  * since it only processes as much of the string as needed to make a
  54  * comparison.
  55  * <p> For example (with strength == tertiary)
  56  * <p>When comparing "Abernathy" to "Baggins-Smythworthy", Collator
  57  * only needs to process a couple of characters, while a comparison
  58  * with CollationKeys will process all of the characters.  On the other hand,
  59  * if you are doing a sort of a number of fields, it is much faster to use
  60  * CollationKeys, since you will be comparing strings multiple times.
  61  * <p>Typical use of CollationKeys are in databases, where you store a CollationKey
  62  * in a hidden field, and use it for sorting or indexing.
  63  *
  64  * <p>Example of use:
  65  * <pre>
  66  * \code
  67  *     UErrorCode success = U_ZERO_ERROR;
  68  *     Collator* myCollator = Collator::createInstance(success);
  69  *     CollationKey* keys = new CollationKey [3];
  70  *     myCollator->getCollationKey("Tom", keys[0], success );
  71  *     myCollator->getCollationKey("Dick", keys[1], success );
  72  *     myCollator->getCollationKey("Harry", keys[2], success );
  73  *
  74  *     // Inside body of sort routine, compare keys this way:
  75  *     CollationKey tmp;
  76  *     if(keys[0].compareTo( keys[1] ) > 0 ) {
  77  *         tmp = keys[0]; keys[0] = keys[1]; keys[1] = tmp;
  78  *     }
  79  *     //...
  80  * \endcode
  81  * </pre>
  82  * <p>Because Collator::compare()'s algorithm is complex, it is faster to sort
  83  * long lists of words by retrieving collation keys with Collator::getCollationKey().
  84  * You can then cache the collation keys and compare them using CollationKey::compareTo().
  85  * <p>
  86  * <strong>Note:</strong> <code>Collator</code>s with different Locale,
  87  * CollationStrength and DecompositionMode settings will return different
  88  * CollationKeys for the same set of strings. Locales have specific
  89  * collation rules, and the way in which secondary and tertiary differences
  90  * are taken into account, for example, will result in different CollationKeys
  91  * for same strings.
  92  * <p>
  93
  94  * @see          Collator
  95  * @see          RuleBasedCollator
  96  * @version      1.3 12/18/96
  97  * @author       Helena Shih
  98  * @stable ICU 2.0
  99  */
 100 class U_I18N_API CollationKey : public UObject {
 101 public:
 102     /**
 103     * This creates an empty collation key based on the null string.  An empty
 104     * collation key contains no sorting information.  When comparing two empty
 105     * collation keys, the result is Collator::EQUAL.  Comparing empty collation key
 106     * with non-empty collation key is always Collator::LESS.
 107     * @stable ICU 2.0
 108     */
 109     CollationKey();
 110
 111
 112     /**
 113     * Creates a collation key based on the collation key values.
 114     * @param values the collation key values
 115     * @param count number of collation key values, including trailing nulls.
 116     * @stable ICU 2.0
 117     */
 118     CollationKey(const  uint8_t*    values,
 119                 int32_t     count);
 120
 121     /**
 122     * Copy constructor.
 123     * @param other    the object to be copied.
 124     * @stable ICU 2.0
 125     */
 126     CollationKey(const CollationKey& other);
 127
 128     /**
 129     * Sort key destructor.
 130     * @stable ICU 2.0
 131     */
 132     virtual ~CollationKey();
 133
 134     /**
 135     * Assignment operator
 136     * @param other    the object to be copied.
 137     * @stable ICU 2.0
 138     */
 139     const   CollationKey&   operator=(const CollationKey& other);
 140
 141     /**
 142     * Compare if two collation keys are the same.
 143     * @param source the collation key to compare to.
 144     * @return Returns true if two collation keys are equal, false otherwise.
 145     * @stable ICU 2.0
 146     */
 147     UBool                   operator==(const CollationKey& source) const;
 148
 149     /**
 150     * Compare if two collation keys are not the same.
 151     * @param source the collation key to compare to.
 152     * @return Returns TRUE if two collation keys are different, FALSE otherwise.
 153     * @stable ICU 2.0
 154     */
 155     UBool                   operator!=(const CollationKey& source) const;
 156
 157
 158     /**
 159     * Test to see if the key is in an invalid state. The key will be in an
 160     * invalid state if it couldn't allocate memory for some operation.
 161     * @return Returns TRUE if the key is in an invalid, FALSE otherwise.
 162     * @stable ICU 2.0
 163     */
 164     UBool                   isBogus(void) const;
 165
 166     /**
 167     * Returns a pointer to the collation key values. The storage is owned
 168     * by the collation key and the pointer will become invalid if the key
 169     * is deleted.
 170     * @param count the output parameter of number of collation key values,
 171     * including any trailing nulls.
 172     * @return a pointer to the collation key values.
 173     * @stable ICU 2.0
 174     */
 175     const    uint8_t*       getByteArray(int32_t& count) const;
 176
 177 #ifdef U_USE_COLLATION_KEY_DEPRECATES
 178     /**
 179     * Extracts the collation key values into a new array. The caller owns
 180     * this storage and should free it.
 181     * @param count the output parameter of number of collation key values,
 182     * including any trailing nulls.
 183     * @obsolete ICU 2.6. Use getByteArray instead since this API will be removed in that release.
 184     */
 185     uint8_t*                toByteArray(int32_t& count) const;
 186 #endif
 187
 188 #ifndef U_HIDE_DEPRECATED_API
 189     /**
 190     * Convenience method which does a string(bit-wise) comparison of the
 191     * two collation keys.
 192     * @param target target collation key to be compared with
 193     * @return Returns Collator::LESS if sourceKey &lt; targetKey,
 194     * Collator::GREATER if sourceKey > targetKey and Collator::EQUAL
 195     * otherwise.
 196     * @deprecated ICU 2.6 use the overload with error code
 197     */
 198     Collator::EComparisonResult compareTo(const CollationKey& target) const;
 199 #endif  /* U_HIDE_DEPRECATED_API */
 200
 201     /**
 202     * Convenience method which does a string(bit-wise) comparison of the
 203     * two collation keys.
 204     * @param target target collation key to be compared with
 205     * @param status error code
 206     * @return Returns UCOL_LESS if sourceKey &lt; targetKey,
 207     * UCOL_GREATER if sourceKey > targetKey and UCOL_EQUAL
 208     * otherwise.
 209     * @stable ICU 2.6
 210     */
 211     UCollationResult compareTo(const CollationKey& target, UErrorCode &status) const;
 212
 213     /**
 214     * Creates an integer that is unique to the collation key.  NOTE: this
 215     * is not the same as String.hashCode.
 216     * <p>Example of use:
 217     * <pre>
 218     * .    UErrorCode status = U_ZERO_ERROR;
 219     * .    Collator *myCollation = Collator::createInstance(Locale::US, status);
 220     * .    if (U_FAILURE(status)) return;
 221     * .    CollationKey key1, key2;
 222     * .    UErrorCode status1 = U_ZERO_ERROR, status2 = U_ZERO_ERROR;
 223     * .    myCollation->getCollationKey("abc", key1, status1);
 224     * .    if (U_FAILURE(status1)) { delete myCollation; return; }
 225     * .    myCollation->getCollationKey("ABC", key2, status2);
 226     * .    if (U_FAILURE(status2)) { delete myCollation; return; }
 227     * .    // key1.hashCode() != key2.hashCode()
 228     * </pre>
 229     * @return the hash value based on the string's collation order.
 230     * @see UnicodeString#hashCode
 231     * @stable ICU 2.0
 232     */
 233     int32_t                 hashCode(void) const;
 234
 235     /**
 236      * ICU "poor man's RTTI", returns a UClassID for the actual class.
 237      * @stable ICU 2.2
 238      */
 239     virtual UClassID getDynamicClassID() const;
 240
 241     /**
 242      * ICU "poor man's RTTI", returns a UClassID for this class.
 243      * @stable ICU 2.2
 244      */
 245     static UClassID U_EXPORT2 getStaticClassID();
 246
 247 private:
 248     /**
 249      * Replaces the current bytes buffer with a new one of newCapacity
 250      * and copies length bytes from the old buffer to the new one.
 251      * @return the new buffer, or NULL if the allocation failed
 252      */
 253     uint8_t *reallocate(int32_t newCapacity, int32_t length);
 254     /**
 255      * Set a new length for a new sort key in the existing fBytes.
 256      */
 257     void setLength(int32_t newLength);
 258
 259     uint8_t *getBytes() {
 260         return (fFlagAndLength >= 0) ? fUnion.fStackBuffer : fUnion.fFields.fBytes;
 261     }
 262     const uint8_t *getBytes() const {
 263         return (fFlagAndLength >= 0) ? fUnion.fStackBuffer : fUnion.fFields.fBytes;
 264     }
 265     int32_t getCapacity() const {
 266         return (fFlagAndLength >= 0) ? (int32_t)sizeof(fUnion) : fUnion.fFields.fCapacity;
 267     }
 268     int32_t getLength() const { return fFlagAndLength & 0x7fffffff; }
 269
 270     /**
 271     * Set the CollationKey to a "bogus" or invalid state
 272     * @return this CollationKey
 273     */
 274     CollationKey&           setToBogus(void);
 275     /**
 276     * Resets this CollationKey to an empty state
 277     * @return this CollationKey
 278     */
 279     CollationKey&           reset(void);
 280
 281     /**
 282     * Allow private access to RuleBasedCollator
 283     */
 284     friend  class           RuleBasedCollator;
 285     friend  class           CollationKeyByteSink;
 286
 287     // Class fields. sizeof(CollationKey) is intended to be 48 bytes
 288     // on a machine with 64-bit pointers.
 289     // We use a union to maximize the size of the internal buffer,
 290     // similar to UnicodeString but not as tight and complex.
 291
 292     // (implicit) *vtable;
 293     /**
 294      * Sort key length and flag.
 295      * Bit 31 is set if the buffer is heap-allocated.
 296      * Bits 30..0 contain the sort key length.
 297      */
 298     int32_t fFlagAndLength;
 299     /**
 300     * Unique hash value of this CollationKey.
 301     * Special value 2 if the key is bogus.
 302     */
 303     mutable int32_t fHashCode;
 304     /**
 305      * fUnion provides 32 bytes for the internal buffer or for
 306      * pointer+capacity.
 307      */
 308     union StackBufferOrFields {
 309         /** fStackBuffer is used iff fFlagAndLength>=0, else fFields is used */
 310         uint8_t fStackBuffer[32];
 311         struct {
 312             uint8_t *fBytes;
 313             int32_t fCapacity;
 314         } fFields;
 315     } fUnion;
 316 };
 317
 318 inline UBool
 319 CollationKey::operator!=(const CollationKey& other) const
 320 {
 321     return !(*this == other);
 322 }
 323
 324 inline UBool
 325 CollationKey::isBogus() const
 326 {
 327     return fHashCode == 2;  // kBogusHashCode
 328 }
 329
 330 inline const uint8_t*
 331 CollationKey::getByteArray(int32_t &count) const
 332 {
 333     count = getLength();
 334     return getBytes();
 335 }
 336
 337 U_NAMESPACE_END
 338 #endif // U_SHOW_CPLUSPLUS_API
 339
 340 #endif /* #if !UCONFIG_NO_COLLATION */
 341
 342 #endif