2 *******************************************************************************
4 * Copyright (C) 2002-2005, International Business Machines
5 * Corporation and others. All Rights Reserved.
7 *******************************************************************************
13 #include "unicode/uobject.h"
14 #include "unicode/unistr.h"
18 * \brief C++ API: String Enumeration
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.
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
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
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>
50 * ICU 2.8 adds some default implementations and helper functions
55 class U_COMMON_API StringEnumeration : public UObject {
61 virtual ~StringEnumeration();
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.
73 * @return a clone of this object
75 * @see getDynamicClassID
78 virtual StringEnumeration *clone() const;
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>
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>
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
93 * @param status the error code.
94 * @return number of elements in the iterator.
97 virtual int32_t count(UErrorCode& status) const = 0;
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>
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>
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>
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>
119 * Starting with ICU 2.8, the default implementation calls snext()
120 * and handles the conversion.
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.
128 virtual const char* next(int32_t *resultLength, UErrorCode& status);
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>
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>
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>
144 * Starting with ICU 2.8, the default implementation calls snext()
145 * and handles the conversion.
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.
153 virtual const UChar* unext(int32_t *resultLength, UErrorCode& status);
156 * <p>Returns the next element a UnicodeString*. If there are no
157 * more elements, returns NULL.</p>
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>
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>
166 * @param status the error code.
167 * @return a pointer to the string, or NULL.
171 virtual const UnicodeString* snext(UErrorCode& status) = 0;
174 * <p>Resets the iterator. This re-establishes sync with the
175 * service and rewinds the iterator to start at the first
178 * <p>Previous pointers returned by next, unext, or snext become
179 * invalid, and the value returned by count might change.</p>
181 * @param status the error code.
185 virtual void reset(UErrorCode& status) = 0;
189 * UnicodeString field for use with default implementations and subclasses.
192 UnicodeString unistr;
194 * char * default buffer for use with default implementations and subclasses.
197 char charsBuffer[32];
199 * char * buffer for use with default implementations and subclasses.
200 * Allocated in constructor and in ensureCharsCapacity().
205 * Capacity of chars, for use with default implementations and subclasses.
208 int32_t charsCapacity;
211 * Default constructor for use with default implementations and subclasses.
217 * Ensures that chars is at least as large as the requested capacity.
218 * For use with default implementations and subclasses.
220 * @param capacity Requested capacity.
221 * @param status ICU in/out error code.
224 void ensureCharsCapacity(int32_t capacity, UErrorCode &status);
227 * Converts s to Unicode and sets unistr to the result.
228 * For use with default implementations and subclasses,
229 * especially for implementations of snext() in terms of next().
230 * This is provided with a helper function instead of a default implementation
231 * of snext() to avoid potential infinite loops between next() and snext().
235 * const UnicodeString* snext(UErrorCode& status) {
236 * int32_t resultLength=0;
237 * const char *s=next(&resultLength, status);
238 * return setChars(s, resultLength, status);
242 * @param s String to be converted to Unicode.
243 * @param length Length of the string.
244 * @param status ICU in/out error code.
245 * @return A pointer to unistr.
248 UnicodeString *setChars(const char *s, int32_t length, UErrorCode &status);