Re: [icu-design] ICU4C API proposal: C++ move/swap LocalPointer & UnicodeString

[Andy H. <and...@gm...>]

This proposal looks good to me.

  -- Andy

On Fri, May 8, 2015 at 4:40 PM, Markus Scherer <mar...@gm...> wrote:

> (Take 3, sorry about the old addresses on cc...)
>
> On Fri, May 8, 2015 at 4:30 PM, Markus Scherer <mar...@gm...>
> wrote:
>
>> Dear ICU team & users,
>>
>> I would like to propose the following API for: *ICU 56*
>> Please provide feedback by: *Tuesday, 2015-05-19*
>> Designated API reviewer: *Andy*
>> Ticket: http://bugs.icu-project.org/trac/ticket/8324
>> and http://bugs.icu-project.org/trac/ticket/10086
>>
>> I would like to propose for LocalPointer, LocalArray, UnicodeString:
>> - C++11 move constructor & move assignment operator,
>>   #ifdef'ed contingent on compiler support,
>>   and with semantics matching those documented for similar STL classes
>>   (especially unique_ptr and string)
>> - moveFrom() which implements the move assignment but does not require
>> C++11
>> - member and non-member swap
>>
>> In a future proposal I might add these to Formattable and Locale as well.
>>
>> Also adding to LocalArray a constructor which takes a UErrorCode, and
>> adoptInsteadAndCheckErrorCode(), which I seem to have forgotten in ICU 55
>> http://bugs.icu-project.org/trac/ticket/11339 (there does not seem to be
>> a good reason not to have these for arrays).
>>
>> I am adding @internal macros into platform.h for detecting the C++
>> version and whether rvalue references (for move) and noexcept are available.
>>
>> *localpointer.h*
>>
>>     /**
>>      * Move constructor, leaves src with isNull().
>>      * @param src source smart pointer
>>      * @draft ICU 56
>>      */
>>     LocalPointer(LocalPointer<T> &&src) U_NOEXCEPT
>>
>>     /**
>>      * Move assignment operator, leaves src with isNull().
>>      * The behavior is undefined if *this and src are the same object.
>>      * @param src source smart pointer
>>      * @return *this
>>      * @draft ICU 56
>>      */
>>     LocalPointer<T> &operator=(LocalPointer<T> &&src) U_NOEXCEPT
>>     /**
>>      * Move assignment, leaves src with isNull().
>>      * The behavior is undefined if *this and src are the same object.
>>      *
>>      * Can be called explicitly, does not need C++11 support.
>>      * @param src source smart pointer
>>      * @return *this
>>      * @draft ICU 56
>>      */
>>     LocalPointer<T> &moveFrom(LocalPointer<T> &src) U_NOEXCEPT
>>     /**
>>      * Swap pointers.
>>      * @param other other smart pointer
>>      * @draft ICU 56
>>      */
>>     void swap(LocalPointer<T> &other) U_NOEXCEPT
>>
>> /**
>>  * Non-member LocalPointer swap function.
>>  * @param p1 will get p2's pointer
>>  * @param p2 will get p1's pointer
>>  * @draft ICU 56
>>  */
>> template<typename T>
>> inline void swap(LocalPointer<T> &p1, LocalPointer<T> &p2) U_NOEXCEPT
>>
>>     /**
>>      * Constructor takes ownership and reports an error if NULL.
>>      *
>>      * This constructor is intended to be used with other-class
>> constructors
>>      * that may report a failure UErrorCode,
>>      * so that callers need to check only for U_FAILURE(errorCode)
>>      * and not also separately for isNull().
>>      *
>>      * @param p simple pointer to an array of T objects that is adopted
>>      * @param errorCode in/out UErrorCode, set to
>> U_MEMORY_ALLOCATION_ERROR
>>      *     if p==NULL and no other failure code had been set
>>      * @draft ICU 56
>>      */
>>     LocalArray(T *p, UErrorCode &errorCode)
>>     /**
>>      * Move constructor, leaves src with isNull().
>>      * @param src source smart pointer
>>      * @draft ICU 56
>>      */
>>     LocalArray(LocalArray<T> &&src) U_NOEXCEPT
>>
>>     /**
>>      * Move assignment operator, leaves src with isNull().
>>      * The behavior is undefined if *this and src are the same object.
>>      * @param src source smart pointer
>>      * @return *this
>>      * @draft ICU 56
>>      */
>>     LocalArray<T> &operator=(LocalArray<T> &&src) U_NOEXCEPT
>>     /**
>>      * Move assignment, leaves src with isNull().
>>      * The behavior is undefined if *this and src are the same object.
>>      *
>>      * Can be called explicitly, does not need C++11 support.
>>      * @param src source smart pointer
>>      * @return *this
>>      * @draft ICU 56
>>      */
>>     LocalArray<T> &moveFrom(LocalArray<T> &src) U_NOEXCEPT
>>     /**
>>      * Swap pointers.
>>      * @param other other smart pointer
>>      * @draft ICU 56
>>      */
>>     void swap(LocalArray<T> &other) U_NOEXCEPT
>>
>>     /**
>>      * Deletes the array it owns,
>>      * and adopts (takes ownership of) the one passed in.
>>      *
>>      * If U_FAILURE(errorCode), then the current array is retained and
>> the new one deleted.
>>      *
>>      * If U_SUCCESS(errorCode) but the input pointer is NULL,
>>      * then U_MEMORY_ALLOCATION_ERROR is set,
>>      * the current array is deleted, and NULL is set.
>>      *
>>      * @param p simple pointer to an array of T objects that is adopted
>>      * @param errorCode in/out UErrorCode, set to
>> U_MEMORY_ALLOCATION_ERROR
>>      *     if p==NULL and no other failure code had been set
>>      * @draft ICU 56
>>      */
>>     void adoptInsteadAndCheckErrorCode(T *p, UErrorCode &errorCode)
>>
>> /**
>>  * Non-member LocalArray swap function.
>>  * @param p1 will get p2's pointer
>>  * @param p2 will get p1's pointer
>>  * @draft ICU 56
>>  */
>> template<typename T>
>> inline void swap(LocalArray<T> &p1, LocalArray<T> &p2) U_NOEXCEPT
>>
>> *unistr.h*
>>
>>   /**
>>    * Move assignment operator, might leave src in bogus state.
>>    * This string will have the same contents and state that the source
>> string had.
>>    * The behavior is undefined if *this and src are the same object.
>>    * @param src source string
>>    * @return *this
>>    * @draft ICU 56
>>    */
>>   UnicodeString &operator=(UnicodeString &&src) U_NOEXCEPT
>>   /**
>>    * Move assignment, might leave src in bogus state.
>>    * This string will have the same contents and state that the source
>> string had.
>>    * The behavior is undefined if *this and src are the same object.
>>    *
>>    * Can be called explicitly, does not need C++11 support.
>>    * @param src source string
>>    * @return *this
>>    * @draft ICU 56
>>    */
>>   UnicodeString &moveFrom(UnicodeString &src) U_NOEXCEPT;
>>
>>   /**
>>    * Swap strings.
>>    * @param other other string
>>    * @draft ICU 56
>>    */
>>   void swap(UnicodeString &other) U_NOEXCEPT;
>>
>>   /**
>>    * Move constructor, might leave src in bogus state.
>>    * This string will have the same contents and state that the source
>> string had.
>>    * @param src source string
>>    * @draft ICU 56
>>    */
>>   UnicodeString(UnicodeString &&src) U_NOEXCEPT;
>>
>> /**
>>  * Non-member UnicodeString swap function.
>>  * @param s1 will get s2's contents and state
>>  * @param s2 will get s1's contents and state
>>  * @draft ICU 56
>>  */
>> U_COMMON_API inline void U_EXPORT2
>> swap(UnicodeString &s1, UnicodeString &s2) U_NOEXCEPT
>>
>> Sincerely,
>> markus
>>
>
>
>
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