icuSources/i18n/unicode/sortkey.h

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