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