1 /* 2 ******************************************************************************* 3 * 4 * Copyright (C) 2002-2007, 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 * 122 * @param status the error code. 123 * @param resultLength a pointer to receive the length, can be NULL. 124 * @return a pointer to the string, or NULL. 125 * 126 * @stable ICU 2.4 127 */ 128 virtual const char* next(int32_t *resultLength, UErrorCode& status); 129 130 /** 131 * <p>Returns the next element as a NUL-terminated UChar*. If there 132 * are no more elements, returns NULL. If the resultLength pointer 133 * is not NULL, the length of the string (not counting the 134 * terminating NUL) is returned at that address. If an error 135 * status is returned, the value at resultLength is undefined.</p> 136 * 137 * <p>The returned pointer is owned by this iterator and must not be 138 * deleted by the caller. The pointer is valid until the next call 139 * to next, unext, snext, reset, or the enumerator's destructor.</p> 140 * 141 * <p>If the iterator is out of sync with its service, status is set 142 * to U_ENUM_OUT_OF_SYNC_ERROR and NULL is returned.</p> 143 * 144 * Starting with ICU 2.8, the default implementation calls snext() 145 * and handles the conversion. 146 * 147 * @param status the error code. 148 * @param resultLength a ponter to receive the length, can be NULL. 149 * @return a pointer to the string, or NULL. 150 * 151 * @stable ICU 2.4 152 */ 153 virtual const UChar* unext(int32_t *resultLength, UErrorCode& status); 154 155 /** 156 * <p>Returns the next element a UnicodeString*. If there are no 157 * more elements, returns NULL.</p> 158 * 159 * <p>The returned pointer is owned by this iterator and must not be 160 * deleted by the caller. The pointer is valid until the next call 161 * to next, unext, snext, reset, or the enumerator's destructor.</p> 162 * 163 * <p>If the iterator is out of sync with its service, status is set 164 * to U_ENUM_OUT_OF_SYNC_ERROR and NULL is returned.</p> 165 * 166 * @param status the error code. 167 * @return a pointer to the string, or NULL. 168 * 169 * @stable ICU 2.4 170 */ 171 virtual const UnicodeString* snext(UErrorCode& status) = 0; 172 173 /** 174 * <p>Resets the iterator. This re-establishes sync with the 175 * service and rewinds the iterator to start at the first 176 * element.</p> 177 * 178 * <p>Previous pointers returned by next, unext, or snext become 179 * invalid, and the value returned by count might change.</p> 180 * 181 * @param status the error code. 182 * 183 * @stable ICU 2.4 184 */ 185 virtual void reset(UErrorCode& status) = 0; 186 187 /** 188 * Compares this enumeration to other to check if both are equal 189 * 190 * @param that The other string enumeration to compare this object to 191 * @return TRUE if the enumerations are equal. FALSE if not. 192 * @stable ICU 3.6 193 */ 194 virtual UBool operator==(const StringEnumeration& that)const; 195 /** 196 * Compares this enumeration to other to check if both are not 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 UBool operator!=(const StringEnumeration& that)const; 203 204 protected: 205 /** 206 * UnicodeString field for use with default implementations and subclasses. 207 * @stable ICU 2.8 208 */ 209 UnicodeString unistr; 210 /** 211 * char * default buffer for use with default implementations and subclasses. 212 * @stable ICU 2.8 213 */ 214 char charsBuffer[32]; 215 /** 216 * char * buffer for use with default implementations and subclasses. 217 * Allocated in constructor and in ensureCharsCapacity(). 218 * @stable ICU 2.8 219 */ 220 char *chars; 221 /** 222 * Capacity of chars, for use with default implementations and subclasses. 223 * @stable ICU 2.8 224 */ 225 int32_t charsCapacity; 226 227 /** 228 * Default constructor for use with default implementations and subclasses. 229 * @stable ICU 2.8 230 */ 231 StringEnumeration(); 232 233 /** 234 * Ensures that chars is at least as large as the requested capacity. 235 * For use with default implementations and subclasses. 236 * 237 * @param capacity Requested capacity. 238 * @param status ICU in/out error code. 239 * @stable ICU 2.8 240 */ 241 void ensureCharsCapacity(int32_t capacity, UErrorCode &status); 242 243 /** 244 * Converts s to Unicode and sets unistr to the result. 245 * For use with default implementations and subclasses, 246 * especially for implementations of snext() in terms of next(). 247 * This is provided with a helper function instead of a default implementation 248 * of snext() to avoid potential infinite loops between next() and snext(). 249 * 250 * For example: 251 * \code 252 * const UnicodeString* snext(UErrorCode& status) { 253 * int32_t resultLength=0; 254 * const char *s=next(&resultLength, status); 255 * return setChars(s, resultLength, status); 256 * } 257 * \endcode 258 * 259 * @param s String to be converted to Unicode. 260 * @param length Length of the string. 261 * @param status ICU in/out error code. 262 * @return A pointer to unistr. 263 * @stable ICU 2.8 264 */ 265 UnicodeString *setChars(const char *s, int32_t length, UErrorCode &status); 266 }; 267 268 U_NAMESPACE_END 269 270 /* STRENUM_H */ 271 #endif 272