strenum.h (10202B)
1 // © 2016 and later: Unicode, Inc. and others. 2 // License & terms of use: http://www.unicode.org/copyright.html 3 /* 4 ******************************************************************************* 5 * 6 * Copyright (C) 2002-2012, International Business Machines 7 * Corporation and others. All Rights Reserved. 8 * 9 ******************************************************************************* 10 */ 11 12 #ifndef STRENUM_H 13 #define STRENUM_H 14 15 #include "unicode/utypes.h" 16 17 #if U_SHOW_CPLUSPLUS_API 18 19 #include "unicode/uobject.h" 20 #include "unicode/unistr.h" 21 22 /** 23 * \file 24 * \brief C++ API: String Enumeration 25 */ 26 27 U_NAMESPACE_BEGIN 28 29 /** 30 * Base class for 'pure' C++ implementations of uenum api. Adds a 31 * method that returns the next UnicodeString since in C++ this can 32 * be a common storage format for strings. 33 * 34 * <p>The model is that the enumeration is over strings maintained by 35 * a 'service.' At any point, the service might change, invalidating 36 * the enumerator (though this is expected to be rare). The iterator 37 * returns an error if this has occurred. Lack of the error is no 38 * guarantee that the service didn't change immediately after the 39 * call, so the returned string still might not be 'valid' on 40 * subsequent use.</p> 41 * 42 * <p>Strings may take the form of const char*, const char16_t*, or const 43 * UnicodeString*. The type you get is determine by the variant of 44 * 'next' that you call. In general the StringEnumeration is 45 * optimized for one of these types, but all StringEnumerations can 46 * return all types. Returned strings are each terminated with a NUL. 47 * Depending on the service data, they might also include embedded NUL 48 * characters, so API is provided to optionally return the true 49 * length, counting the embedded NULs but not counting the terminating 50 * NUL.</p> 51 * 52 * <p>The pointers returned by next, unext, and snext become invalid 53 * upon any subsequent call to the enumeration's destructor, next, 54 * unext, snext, or reset.</p> 55 * 56 * ICU 2.8 adds some default implementations and helper functions 57 * for subclasses. 58 * 59 * @stable ICU 2.4 60 */ 61 class U_COMMON_API StringEnumeration : public UObject { 62 public: 63 /** 64 * Destructor. 65 * @stable ICU 2.4 66 */ 67 virtual ~StringEnumeration(); 68 69 /** 70 * Clone this object, an instance of a subclass of StringEnumeration. 71 * Clones can be used concurrently in multiple threads. 72 * If a subclass does not implement clone(), or if an error occurs, 73 * then nullptr is returned. 74 * The caller must delete the clone. 75 * 76 * @return a clone of this object 77 * 78 * @see getDynamicClassID 79 * @stable ICU 2.8 80 */ 81 virtual StringEnumeration *clone() const; 82 83 /** 84 * <p>Return the number of elements that the iterator traverses. If 85 * the iterator is out of sync with its service, status is set to 86 * U_ENUM_OUT_OF_SYNC_ERROR, and the return value is zero.</p> 87 * 88 * <p>The return value will not change except possibly as a result of 89 * a subsequent call to reset, or if the iterator becomes out of sync.</p> 90 * 91 * <p>This is a convenience function. It can end up being very 92 * expensive as all the items might have to be pre-fetched 93 * (depending on the storage format of the data being 94 * traversed).</p> 95 * 96 * @param status the error code. 97 * @return number of elements in the iterator. 98 * 99 * @stable ICU 2.4 */ 100 virtual int32_t count(UErrorCode& status) const = 0; 101 102 /** 103 * <p>Returns the next element as a NUL-terminated char*. If there 104 * are no more elements, returns nullptr. If the resultLength pointer 105 * is not nullptr, the length of the string (not counting the 106 * terminating NUL) is returned at that address. If an error 107 * status is returned, the value at resultLength is undefined.</p> 108 * 109 * <p>The returned pointer is owned by this iterator and must not be 110 * deleted by the caller. The pointer is valid until the next call 111 * to next, unext, snext, reset, or the enumerator's destructor.</p> 112 * 113 * <p>If the iterator is out of sync with its service, status is set 114 * to U_ENUM_OUT_OF_SYNC_ERROR and nullptr is returned.</p> 115 * 116 * <p>If the native service string is a char16_t* string, it is 117 * converted to char* with the invariant converter. If the 118 * conversion fails (because a character cannot be converted) then 119 * status is set to U_INVARIANT_CONVERSION_ERROR and the return 120 * value is undefined (though not nullptr).</p> 121 * 122 * Starting with ICU 2.8, the default implementation calls snext() 123 * and handles the conversion. 124 * Either next() or snext() must be implemented differently by a subclass. 125 * 126 * @param status the error code. 127 * @param resultLength a pointer to receive the length, can be nullptr. 128 * @return a pointer to the string, or nullptr. 129 * 130 * @stable ICU 2.4 131 */ 132 virtual const char* next(int32_t *resultLength, UErrorCode& status); 133 134 /** 135 * <p>Returns the next element as a NUL-terminated char16_t*. If there 136 * are no more elements, returns nullptr. If the resultLength pointer 137 * is not nullptr, the length of the string (not counting the 138 * terminating NUL) is returned at that address. If an error 139 * status is returned, the value at resultLength is undefined.</p> 140 * 141 * <p>The returned pointer is owned by this iterator and must not be 142 * deleted by the caller. The pointer is valid until the next call 143 * to next, unext, snext, reset, or the enumerator's destructor.</p> 144 * 145 * <p>If the iterator is out of sync with its service, status is set 146 * to U_ENUM_OUT_OF_SYNC_ERROR and nullptr is returned.</p> 147 * 148 * Starting with ICU 2.8, the default implementation calls snext() 149 * and handles the conversion. 150 * 151 * @param status the error code. 152 * @param resultLength a pointer to receive the length, can be nullptr. 153 * @return a pointer to the string, or nullptr. 154 * 155 * @stable ICU 2.4 156 */ 157 virtual const char16_t* unext(int32_t *resultLength, UErrorCode& status); 158 159 /** 160 * <p>Returns the next element a UnicodeString*. If there are no 161 * more elements, returns nullptr.</p> 162 * 163 * <p>The returned pointer is owned by this iterator and must not be 164 * deleted by the caller. The pointer is valid until the next call 165 * to next, unext, snext, reset, or the enumerator's destructor.</p> 166 * 167 * <p>If the iterator is out of sync with its service, status is set 168 * to U_ENUM_OUT_OF_SYNC_ERROR and nullptr is returned.</p> 169 * 170 * Starting with ICU 2.8, the default implementation calls next() 171 * and handles the conversion. 172 * Either next() or snext() must be implemented differently by a subclass. 173 * 174 * @param status the error code. 175 * @return a pointer to the string, or nullptr. 176 * 177 * @stable ICU 2.4 178 */ 179 virtual const UnicodeString* snext(UErrorCode& status); 180 181 /** 182 * <p>Resets the iterator. This re-establishes sync with the 183 * service and rewinds the iterator to start at the first 184 * element.</p> 185 * 186 * <p>Previous pointers returned by next, unext, or snext become 187 * invalid, and the value returned by count might change.</p> 188 * 189 * @param status the error code. 190 * 191 * @stable ICU 2.4 192 */ 193 virtual void reset(UErrorCode& status) = 0; 194 195 /** 196 * Compares this enumeration to other to check if both are equal 197 * 198 * @param that The other string enumeration to compare this object to 199 * @return true if the enumerations are equal. false if not. 200 * @stable ICU 3.6 201 */ 202 virtual bool operator==(const StringEnumeration& that)const; 203 /** 204 * Compares this enumeration to other to check if both are not equal 205 * 206 * @param that The other string enumeration to compare this object to 207 * @return true if the enumerations are equal. false if not. 208 * @stable ICU 3.6 209 */ 210 virtual bool operator!=(const StringEnumeration& that)const; 211 212 protected: 213 /** 214 * UnicodeString field for use with default implementations and subclasses. 215 * @stable ICU 2.8 216 */ 217 UnicodeString unistr; 218 /** 219 * char * default buffer for use with default implementations and subclasses. 220 * @stable ICU 2.8 221 */ 222 char charsBuffer[32]; 223 /** 224 * char * buffer for use with default implementations and subclasses. 225 * Allocated in constructor and in ensureCharsCapacity(). 226 * @stable ICU 2.8 227 */ 228 char *chars; 229 /** 230 * Capacity of chars, for use with default implementations and subclasses. 231 * @stable ICU 2.8 232 */ 233 int32_t charsCapacity; 234 235 /** 236 * Default constructor for use with default implementations and subclasses. 237 * @stable ICU 2.8 238 */ 239 StringEnumeration(); 240 241 /** 242 * Ensures that chars is at least as large as the requested capacity. 243 * For use with default implementations and subclasses. 244 * 245 * @param capacity Requested capacity. 246 * @param status ICU in/out error code. 247 * @stable ICU 2.8 248 */ 249 void ensureCharsCapacity(int32_t capacity, UErrorCode &status); 250 251 /** 252 * Converts s to Unicode and sets unistr to the result. 253 * For use with default implementations and subclasses, 254 * especially for implementations of snext() in terms of next(). 255 * This is provided with a helper function instead of a default implementation 256 * of snext() to avoid potential infinite loops between next() and snext(). 257 * 258 * For example: 259 * \code 260 * const UnicodeString* snext(UErrorCode& status) { 261 * int32_t resultLength=0; 262 * const char *s=next(&resultLength, status); 263 * return setChars(s, resultLength, status); 264 * } 265 * \endcode 266 * 267 * @param s String to be converted to Unicode. 268 * @param length Length of the string. 269 * @param status ICU in/out error code. 270 * @return A pointer to unistr. 271 * @stable ICU 2.8 272 */ 273 UnicodeString *setChars(const char *s, int32_t length, UErrorCode &status); 274 }; 275 276 U_NAMESPACE_END 277 278 #endif /* U_SHOW_CPLUSPLUS_API */ 279 280 /* STRENUM_H */ 281 #endif