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