sortkey.h revision c73f511526464f8e56c242df80552e9b0d94ae3d
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 37U_NAMESPACE_BEGIN 38 39/* forward declaration */ 40class RuleBasedCollator; 41class 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 */ 97class U_I18N_API CollationKey : public UObject { 98public: 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 < 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 < 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 244private: 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 315inline UBool 316CollationKey::operator!=(const CollationKey& other) const 317{ 318 return !(*this == other); 319} 320 321inline UBool 322CollationKey::isBogus() const 323{ 324 return fHashCode == 2; // kBogusHashCode 325} 326 327inline const uint8_t* 328CollationKey::getByteArray(int32_t &count) const 329{ 330 count = getLength(); 331 return getBytes(); 332} 333 334U_NAMESPACE_END 335 336#endif /* #if !UCONFIG_NO_COLLATION */ 337 338#endif 339