// © 2016 and later: Unicode, Inc. and others.
// License & terms of use: http://www.unicode.org/copyright.html
/*
*******************************************************************************
*
* Copyright (C) 2002-2012, International Business Machines
* Corporation and others. All Rights Reserved.
*
*******************************************************************************
*/
#ifndef STRENUM_H
#define STRENUM_H
#include "unicode/uobject.h"
#include "unicode/unistr.h"
/**
* \file
* \brief C++ API: String Enumeration
*/
U_NAMESPACE_BEGIN
/**
* Base class for 'pure' C++ implementations of uenum api. Adds a
* method that returns the next UnicodeString since in C++ this can
* be a common storage format for strings.
*
* <p>The model is that the enumeration is over strings maintained by
* a 'service.' At any point, the service might change, invalidating
* the enumerator (though this is expected to be rare). The iterator
* returns an error if this has occurred. Lack of the error is no
* guarantee that the service didn't change immediately after the
* call, so the returned string still might not be 'valid' on
* subsequent use.</p>
*
* <p>Strings may take the form of const char*, const char16_t*, or const
* UnicodeString*. The type you get is determine by the variant of
* 'next' that you call. In general the StringEnumeration is
* optimized for one of these types, but all StringEnumerations can
* return all types. Returned strings are each terminated with a NUL.
* Depending on the service data, they might also include embedded NUL
* characters, so API is provided to optionally return the true
* length, counting the embedded NULs but not counting the terminating
* NUL.</p>
*
* <p>The pointers returned by next, unext, and snext become invalid
* upon any subsequent call to the enumeration's destructor, next,
* unext, snext, or reset.</p>
*
* ICU 2.8 adds some default implementations and helper functions
* for subclasses.
*
* @stable ICU 2.4
*/
class U_COMMON_API StringEnumeration : public UObject {
public:
/**
* Destructor.
* @stable ICU 2.4
*/
virtual ~StringEnumeration();
/**
* Clone this object, an instance of a subclass of StringEnumeration.
* Clones can be used concurrently in multiple threads.
* If a subclass does not implement clone(), or if an error occurs,
* then NULL is returned.
* The clone functions in all subclasses return a base class pointer
* because some compilers do not support covariant (same-as-this)
* return types; cast to the appropriate subclass if necessary.
* The caller must delete the clone.
*
* @return a clone of this object
*
* @see getDynamicClassID
* @stable ICU 2.8
*/
virtual StringEnumeration *clone() const;
/**
* <p>Return the number of elements that the iterator traverses. If
* the iterator is out of sync with its service, status is set to
* U_ENUM_OUT_OF_SYNC_ERROR, and the return value is zero.</p>
*
* <p>The return value will not change except possibly as a result of
* a subsequent call to reset, or if the iterator becomes out of sync.</p>
*
* <p>This is a convenience function. It can end up being very
* expensive as all the items might have to be pre-fetched
* (depending on the storage format of the data being
* traversed).</p>
*
* @param status the error code.
* @return number of elements in the iterator.
*
* @stable ICU 2.4 */
virtual int32_t count(UErrorCode& status) const = 0;
/**
* <p>Returns the next element as a NUL-terminated char*. If there
* are no more elements, returns NULL. If the resultLength pointer
* is not NULL, the length of the string (not counting the
* terminating NUL) is returned at that address. If an error
* status is returned, the value at resultLength is undefined.</p>
*
* <p>The returned pointer is owned by this iterator and must not be
* deleted by the caller. The pointer is valid until the next call
* to next, unext, snext, reset, or the enumerator's destructor.</p>
*
* <p>If the iterator is out of sync with its service, status is set
* to U_ENUM_OUT_OF_SYNC_ERROR and NULL is returned.</p>
*
* <p>If the native service string is a char16_t* string, it is
* converted to char* with the invariant converter. If the
* conversion fails (because a character cannot be converted) then
* status is set to U_INVARIANT_CONVERSION_ERROR and the return
* value is undefined (though not NULL).</p>
*
* Starting with ICU 2.8, the default implementation calls snext()
* and handles the conversion.
* Either next() or snext() must be implemented differently by a subclass.
*
* @param status the error code.
* @param resultLength a pointer to receive the length, can be NULL.
* @return a pointer to the string, or NULL.
*
* @stable ICU 2.4
*/
virtual const char* next(int32_t *resultLength, UErrorCode& status);
/**
* <p>Returns the next element as a NUL-terminated char16_t*. If there
* are no more elements, returns NULL. If the resultLength pointer
* is not NULL, the length of the string (not counting the
* terminating NUL) is returned at that address. If an error
* status is returned, the value at resultLength is undefined.</p>
*
* <p>The returned pointer is owned by this iterator and must not be
* deleted by the caller. The pointer is valid until the next call
* to next, unext, snext, reset, or the enumerator's destructor.</p>
*
* <p>If the iterator is out of sync with its service, status is set
* to U_ENUM_OUT_OF_SYNC_ERROR and NULL is returned.</p>
*
* Starting with ICU 2.8, the default implementation calls snext()
* and handles the conversion.
*
* @param status the error code.
* @param resultLength a ponter to receive the length, can be NULL.
* @return a pointer to the string, or NULL.
*
* @stable ICU 2.4
*/
virtual const char16_t* unext(int32_t *resultLength, UErrorCode& status);
/**
* <p>Returns the next element a UnicodeString*. If there are no
* more elements, returns NULL.</p>
*
* <p>The returned pointer is owned by this iterator and must not be
* deleted by the caller. The pointer is valid until the next call
* to next, unext, snext, reset, or the enumerator's destructor.</p>
*
* <p>If the iterator is out of sync with its service, status is set
* to U_ENUM_OUT_OF_SYNC_ERROR and NULL is returned.</p>
*
* Starting with ICU 2.8, the default implementation calls next()
* and handles the conversion.
* Either next() or snext() must be implemented differently by a subclass.
*
* @param status the error code.
* @return a pointer to the string, or NULL.
*
* @stable ICU 2.4
*/
virtual const UnicodeString* snext(UErrorCode& status);
/**
* <p>Resets the iterator. This re-establishes sync with the
* service and rewinds the iterator to start at the first
* element.</p>
*
* <p>Previous pointers returned by next, unext, or snext become
* invalid, and the value returned by count might change.</p>
*
* @param status the error code.
*
* @stable ICU 2.4
*/
virtual void reset(UErrorCode& status) = 0;
/**
* Compares this enumeration to other to check if both are equal
*
* @param that The other string enumeration to compare this object to
* @return TRUE if the enumerations are equal. FALSE if not.
* @stable ICU 3.6
*/
virtual UBool operator==(const StringEnumeration& that)const;
/**
* Compares this enumeration to other to check if both are not equal
*
* @param that The other string enumeration to compare this object to
* @return TRUE if the enumerations are equal. FALSE if not.
* @stable ICU 3.6
*/
virtual UBool operator!=(const StringEnumeration& that)const;
protected:
/**
* UnicodeString field for use with default implementations and subclasses.
* @stable ICU 2.8
*/
UnicodeString unistr;
/**
* char * default buffer for use with default implementations and subclasses.
* @stable ICU 2.8
*/
char charsBuffer[32];
/**
* char * buffer for use with default implementations and subclasses.
* Allocated in constructor and in ensureCharsCapacity().
* @stable ICU 2.8
*/
char *chars;
/**
* Capacity of chars, for use with default implementations and subclasses.
* @stable ICU 2.8
*/
int32_t charsCapacity;
/**
* Default constructor for use with default implementations and subclasses.
* @stable ICU 2.8
*/
StringEnumeration();
/**
* Ensures that chars is at least as large as the requested capacity.
* For use with default implementations and subclasses.
*
* @param capacity Requested capacity.
* @param status ICU in/out error code.
* @stable ICU 2.8
*/
void ensureCharsCapacity(int32_t capacity, UErrorCode &status);
/**
* Converts s to Unicode and sets unistr to the result.
* For use with default implementations and subclasses,
* especially for implementations of snext() in terms of next().
* This is provided with a helper function instead of a default implementation
* of snext() to avoid potential infinite loops between next() and snext().
*
* For example:
* \code
* const UnicodeString* snext(UErrorCode& status) {
* int32_t resultLength=0;
* const char *s=next(&resultLength, status);
* return setChars(s, resultLength, status);
* }
* \endcode
*
* @param s String to be converted to Unicode.
* @param length Length of the string.
* @param status ICU in/out error code.
* @return A pointer to unistr.
* @stable ICU 2.8
*/
UnicodeString *setChars(const char *s, int32_t length, UErrorCode &status);
};
U_NAMESPACE_END
/* STRENUM_H */
#endif
