icuSources/common/unicode/strenum.h

   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