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 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679 680 681 682 683 684 685 686 687 688 689 690 691 692 693 694 695 696 697 698 699 700  /**************************************************************************** ** ** Copyright (C) 2020 Klarälvdalens Datakonsult AB, a KDAB Group company, info@kdab.com, author Marc Mutz ** Contact: https://www.qt.io/licensing/ ** ** This file is part of the documentation of the Qt Toolkit. ** ** $QT_BEGIN_LICENSE:FDL$ ** Commercial License Usage ** Licensees holding valid commercial Qt licenses may use this file in ** accordance with the commercial license agreement provided with the ** Software or, alternatively, in accordance with the terms contained in ** a written agreement between you and The Qt Company. For licensing terms ** and conditions see https://www.qt.io/terms-conditions. For further ** information use the contact form at https://www.qt.io/contact-us. ** ** GNU Free Documentation License Usage ** Alternatively, this file may be used under the terms of the GNU Free ** Documentation License version 1.3 as published by the Free Software ** Foundation and appearing in the file included in the packaging of ** this file. Please review the following information to ensure ** the GNU Free Documentation License version 1.3 requirements ** will be met: https://www.gnu.org/licenses/fdl-1.3.html. ** $QT_END_LICENSE$ ** ****************************************************************************/ /*! \class QUtf8StringView \inmodule QtCore \since 6.0 \brief The QUtf8StringView class provides a unified view on UTF-8 strings with a read-only subset of the QString API. \reentrant \ingroup tools \ingroup string-processing A QUtf8StringView references a contiguous portion of a UTF-8 string it does not own. It acts as an interface type to all kinds of UTF-8 string, without the need to construct a QString or QByteArray first. The UTF-8 string may be represented as an array (or an array-compatible data-structure such as std::basic_string, etc.) of \c char8_t, \c char, \c{signed char} or \c{unsigned char}. QUtf8StringView is designed as an interface type; its main use-case is as a function parameter type. When QUtf8StringViews are used as automatic variables or data members, care must be taken to ensure that the referenced string data (for example, owned by a std::u8string) outlives the QUtf8StringView on all code paths, lest the string view ends up referencing deleted data. When used as an interface type, QUtf8StringView allows a single function to accept a wide variety of UTF-8 string data sources. One function accepting QUtf8StringView thus replaces several function overloads (taking e.g. QByteArray), while at the same time enabling even more string data sources to be passed to the function, such as \c{u8"Hello World"}, a \c char8_t (C++20) or \c char (C++17) string literal. The \c char8_t incompatibility between C++17 and C++20 goes away when using QUtf8StringView. Like all views, QUtf8StringViews should be passed by value, not by reference-to-const: \snippet code/src_corelib_text_qutf8stringview.cpp 0 If you want to give your users maximum freedom in what strings they can pass to your function, consider using QAnyStringView instead. QUtf8StringView can also be used as the return value of a function. If you call a function returning QUtf8StringView, take extra care to not keep the QUtf8StringView around longer than the function promises to keep the referenced string data alive. If in doubt, obtain a strong reference to the data by calling toString() to convert the QUtf8StringView into a QString. QUtf8StringView is a \e{Literal Type}. \section2 Compatible Character Types QUtf8StringView accepts strings over a variety of character types: \list \li \c char (both signed and unsigned) \li \c char8_t (C++20 only) \endlist \section2 Sizes and Sub-Strings All sizes and positions in QUtf8StringView functions are in UTF-8 code points (that is, UTF-8 multibyte sequences count as two, three or four, depending on their length). QUtf8StringView does not an attempt to detect or prevent slicing right through UTF-8 multibyte sequences. This is similar to the situation with QStringView and surrogate pairs. \section2 C++20, char8_t, and QUtf8StringView In C++20, \c{u8""} string literals changed their type from \c{const char[]} to \c{const char8_t[]}. If Qt 6 could have depended on C++20, QUtf8StringView would store \c char8_t natively, and the following functions and aliases would use (pointers to) \c char8_t: \list \li storage_type, value_type, etc \li begin(), end(), data(), etc \li front(), back(), at(), operator[]() \endlist This is what QUtf8StringView is expected to look like in Qt 7, but for Qt 6, this was not possible. Instead of locking users into a C++17-era interface for the next decade, Qt provides two QUtf8StringView classes, in different (inline) namespaces. The first, in namespace \c{q_no_char8_t}, has a value_type of \c{const char} and is universally available. The second, in namespace \c{q_has_char8_t}, has a value_type of \c{const char8_t} and is only available when compiling in C++20 mode. \c{q_no_char8_t} is an inline namespace regardless of C++ edition, to avoid accidental binary incompatibilities. To use the \c{char8_t} version, you need to name it explicitly with \c{q_has_char8_t::QUtf8StringView}. Internally, both are instantiations of the same template class, QBasicUtf8StringView. Please do not use the template class's name in your source code. \sa QAnyStringView, QUtf8StringView, QString */ /*! \typedef QUtf8StringView::storage_type Alias for \c{char}. */ /*! \typedef QUtf8StringView::value_type Alias for \c{const char}. Provided for compatibility with the STL. */ /*! \typedef QUtf8StringView::difference_type Alias for \c{std::ptrdiff_t}. Provided for compatibility with the STL. */ /*! \typedef QUtf8StringView::size_type Alias for qsizetype. Provided for compatibility with the STL. */ /*! \typedef QUtf8StringView::reference Alias for \c{value_type &}. Provided for compatibility with the STL. QUtf8StringView does not support mutable references, so this is the same as const_reference. */ /*! \typedef QUtf8StringView::const_reference Alias for \c{value_type &}. Provided for compatibility with the STL. */ /*! \typedef QUtf8StringView::pointer Alias for \c{value_type *}. Provided for compatibility with the STL. QUtf8StringView does not support mutable pointers, so this is the same as const_pointer. */ /*! \typedef QUtf8StringView::const_pointer Alias for \c{value_type *}. Provided for compatibility with the STL. */ /*! \typedef QUtf8StringView::iterator This typedef provides an STL-style const iterator for QUtf8StringView. QUtf8StringView does not support mutable iterators, so this is the same as const_iterator. \sa const_iterator, reverse_iterator */ /*! \typedef QUtf8StringView::const_iterator This typedef provides an STL-style const iterator for QUtf8StringView. \sa iterator, const_reverse_iterator */ /*! \typedef QUtf8StringView::reverse_iterator This typedef provides an STL-style const reverse iterator for QUtf8StringView. QUtf8StringView does not support mutable reverse iterators, so this is the same as const_reverse_iterator. \sa const_reverse_iterator, iterator */ /*! \typedef QUtf8StringView::const_reverse_iterator This typedef provides an STL-style const reverse iterator for QUtf8StringView. \sa reverse_iterator, const_iterator */ /*! \fn QUtf8StringView::QUtf8StringView() Constructs a null string view. \sa isNull() */ /*! \fn QUtf8StringView::QUtf8StringView(std::nullptr_t) Constructs a null string view. \sa isNull() */ /*! \fn template QUtf8StringView::QUtf8StringView(const Char *str, qsizetype len) Constructs a string view on \a str with length \a len. The range \c{[str,len)} must remain valid for the lifetime of this string view object. Passing \nullptr as \a str is safe if \a len is 0, too, and results in a null string view. The behavior is undefined if \a len is negative or, when positive, if \a str is \nullptr. This constructor only participates in overload resolution if \c Char is a compatible character type. The compatible character types are: \c char8_t, \c char, \c{signed char} and \c{unsigned char}. */ /*! \fn template QUtf8StringView::QUtf8StringView(const Char *first, const Char *last) Constructs a string view on \a first with length (\a last - \a first). The range \c{[first,last)} must remain valid for the lifetime of this string view object. Passing \c \nullptr as \a first is safe if \a last is \nullptr, too, and results in a null string view. The behavior is undefined if \a last precedes \a first, or \a first is \nullptr and \a last is not. This constructor only participates in overload resolution if \c Char is a compatible character type. The compatible character types are: \c char8_t, \c char, \c{signed char} and \c{unsigned char}. */ /*! \fn template QUtf8StringView::QUtf8StringView(const Char *str) Constructs a string view on \a str. The length is determined by scanning for the first \c{Char(0)}. \a str must remain valid for the lifetime of this string view object. Passing \nullptr as \a str is safe and results in a null string view. This constructor only participates in overload resolution if \a str is not an array and if \c Char is a compatible character type. The compatible character types are: \c char8_t, \c char, \c{signed char} and \c{unsigned char}. */ /*! \fn template QUtf8StringView::QUtf8StringView(const Char (&string)[N]) Constructs a string view on the character string literal \a string. The view covers the array until the first \c{Char(0)} is encountered, or \c N, whichever comes first. If you need the full array, use fromArray() instead. \a string must remain valid for the lifetime of this string view object. This constructor only participates in overload resolution if \a string is an actual array and if \c Char is a compatible character type. The compatible character types are: \c char8_t, \c char, \c{signed char} and \c{unsigned char}. \sa fromArray() */ /*! \fn template > QUtf8StringView::QUtf8StringView(const Container &str) Constructs a string view on \a str. The length is taken from \c{str.size()}. \c{str.data()} must remain valid for the lifetime of this string view object. This constructor only participates in overload resolution if \c Container is an instantiation of \c std::basic_string with a compatible character type. The compatible character types are: \c char8_t, \c char, \c{signed char} and \c{unsigned char}. The string view will be empty if and only if \c{str.empty()}. It is unspecified whether this constructor can result in a null string view (\c{str.data()} would have to return \nullptr for this). \sa isNull(), isEmpty() */ /*! \fn template > QUtf8StringView::fromArray(const Char (&string)[Size]) Constructs a string view on the full character string literal \a string, including any trailing \c{Char(0)}. If you don't want the null-terminator included in the view then you can chop() it off when you are certain it is at the end. Alternatively you can use the constructor overload taking an array literal which will create a view up to, but not including, the first null-terminator in the data. \a string must remain valid for the lifetime of this string view object. This function will work with any array literal if \c Char is a compatible character type. The compatible character types are: \c char8_t, \c char, \c{signed char} and \c{unsigned char}. */ /*! \fn QString QUtf8StringView::toString() const Returns a deep copy of this string view's data as a QString. The return value will be a null QString if and only if this string view is null. */ /*! \fn QUtf8StringView::data() const Returns a const pointer to the first code point in the string. \note The character array represented by the return value is \e not null-terminated. \sa begin(), end(), utf8() */ /*! \fn QUtf8StringView::utf8() const Returns a const pointer to the first code point in the string. The result is returned as a \c{const char8_t*}, so this function is only available when compiling in C++20 mode. \note The character array represented by the return value is \e not null-terminated. \sa begin(), end(), data() */ /*! \fn QUtf8StringView::const_iterator QUtf8StringView::begin() const Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the first code point in the string. This function is provided for STL compatibility. \sa end(), cbegin(), rbegin(), data() */ /*! \fn QUtf8StringView::const_iterator QUtf8StringView::cbegin() const Same as begin(). This function is provided for STL compatibility. \sa cend(), begin(), crbegin(), data() */ /*! \fn QUtf8StringView::const_iterator QUtf8StringView::end() const Returns a const \l{STL-style iterators}{STL-style iterator} pointing to the imaginary code point after the last code point in the list. This function is provided for STL compatibility. \sa begin(), cend(), rend() */ /*! \fn QUtf8StringView::const_iterator QUtf8StringView::cend() const Same as end(). This function is provided for STL compatibility. \sa cbegin(), end(), crend() */ /*! \fn QUtf8StringView::const_reverse_iterator QUtf8StringView::rbegin() const Returns a const \l{STL-style iterators}{STL-style} reverse iterator pointing to the first code point in the string, in reverse order. This function is provided for STL compatibility. \sa rend(), crbegin(), begin() */ /*! \fn QUtf8StringView::const_reverse_iterator QUtf8StringView::crbegin() const Same as rbegin(). This function is provided for STL compatibility. \sa crend(), rbegin(), cbegin() */ /*! \fn QUtf8StringView::const_reverse_iterator QUtf8StringView::rend() const Returns a \l{STL-style iterators}{STL-style} reverse iterator pointing to one past the last code point in the string, in reverse order. This function is provided for STL compatibility. \sa rbegin(), crend(), end() */ /*! \fn QUtf8StringView::const_reverse_iterator QUtf8StringView::crend() const Same as rend(). This function is provided for STL compatibility. \sa crbegin(), rend(), cend() */ /*! \fn bool QUtf8StringView::empty() const Returns whether this string view is empty - that is, whether \c{size() == 0}. This function is provided for STL compatibility. \sa isEmpty(), isNull(), size(), length() */ /*! \fn bool QUtf8StringView::isEmpty() const Returns whether this string view is empty - that is, whether \c{size() == 0}. This function is provided for compatibility with other Qt containers. \sa empty(), isNull(), size(), length() */ /*! \fn bool QUtf8StringView::isNull() const Returns whether this string view is null - that is, whether \c{data() == nullptr}. This functions is provided for compatibility with other Qt containers. \sa empty(), isEmpty(), size(), length() */ /*! \fn qsizetype QUtf8StringView::size() const Returns the size of this string view, in UTF-8 code points (that is, multi-byte sequences count as more than one for the purposes of this function, the same as surrogate pairs in QString and QStringView). \sa empty(), isEmpty(), isNull(), length() */ /*! \fn int QUtf8StringView::length() const \obsolete Use size() and port callers to qsizetype. Same as size(), except returns the result as an \c int. This function is provided for compatibility with other Qt containers. \warning QUtf8StringView can represent strings with more than 2\sup{31} code points. Calling this function on a string view for which size() returns a value greater than \c{INT_MAX} constitutes undefined behavior. \sa empty(), isEmpty(), isNull(), size() */ /*! \fn QUtf8StringView::operator[](qsizetype n) const Returns the code point at position \a n in this string view. The behavior is undefined if \a n is negative or not less than size(). \sa at(), front(), back() */ /*! \fn QUtf8StringView::at(qsizetype n) const Returns the code point at position \a n in this string view. The behavior is undefined if \a n is negative or not less than size(). \sa operator[](), front(), back() */ /*! \fn QUtf8StringView::front() const Returns the first code point in the string. Same as first(). This function is provided for STL compatibility. \warning Calling this function on an empty string view constitutes undefined behavior. \sa back() */ /*! \fn QUtf8StringView::back() const Returns the last code point in the string. Same as last(). This function is provided for STL compatibility. \warning Calling this function on an empty string view constitutes undefined behavior. \sa front() */ /*! \fn QUtf8StringView::mid(qsizetype pos, qsizetype n) const Returns the substring of length \a n starting at position \a pos in this object. \obsolete Use sliced() instead in new code. Returns an empty string view if \a n exceeds the length of the string. If there are less than \a n code points available in the string starting at \a pos, or if \a n is negative (default), the function returns all code points that are available from \a pos. \sa first(), last(), sliced(), chopped(), chop(), truncate() */ /*! \fn QUtf8StringView::left(qsizetype n) const \obsolete Use first() instead in new code. Returns the substring of length \a n starting at position 0 in this object. The entire string is returned if \a n is greater than or equal to size(), or less than zero. \sa first(), last(), sliced(), chopped(), chop(), truncate() */ /*! \fn QUtf8StringView::right(qsizetype n) const \obsolete Use last() instead in new code. Returns the substring of length \a n starting at position size() - \a n in this object. The entire string is returned if \a n is greater than or equal to size(), or less than zero. \sa first(), last(), sliced(), chopped(), chop(), truncate() */ /*! \fn QUtf8StringView::first(qsizetype n) const Returns a string view that contains the first \a n code points of this string. \note The behavior is undefined when \a n < 0 or \a n > size(). \sa last(), sliced(), chopped(), chop(), truncate() */ /*! \fn QUtf8StringView::last(qsizetype n) const Returns a string view that contains the last \a n code points of this string. \note The behavior is undefined when \a n < 0 or \a n > size(). \sa first(), sliced(), chopped(), chop(), truncate() */ /*! \fn QUtf8StringView::sliced(qsizetype pos, qsizetype n) const Returns a string view containing \a n code points of this string view, starting at position \a pos. \note The behavior is undefined when \a pos < 0, \a n < 0, or \a pos + \a n > size(). \sa first(), last(), chopped(), chop(), truncate() */ /*! \fn QUtf8StringView::sliced(qsizetype pos) const Returns a string view starting at position \a pos in this object, and extending to its end. \note The behavior is undefined when \a pos < 0 or \a pos > size(). \sa first(), last(), chopped(), chop(), truncate() */ /*! \fn QUtf8StringView::chopped(qsizetype n) const Returns the substring of length size() - \a n starting at the beginning of this object. Same as \c{first(size() - n)}. \note The behavior is undefined when \a n < 0 or \a n > size(). \sa sliced(), first(), last(), chop(), truncate() */ /*! \fn QUtf8StringView::truncate(qsizetype n) Truncates this string view to \a n code points. Same as \c{*this = first(n)}. \note The behavior is undefined when \a n < 0 or \a n > size(). \sa sliced(), first(), last(), chopped(), chop() */ /*! \fn QUtf8StringView::chop(qsizetype n) Truncates this string view by \a n code points. Same as \c{*this = first(size() - n)}. \note The behavior is undefined when \a n < 0 or \a n > size(). \sa sliced(), first(), last(), chopped(), truncate() */ /*! \fn template qToUtf8StringViewIgnoringNull(const QStringLike &s); \relates QUtf8StringView \internal Convert \a s to a QUtf8StringView ignoring \c{s.isNull()}. Returns a string-view that references \a{s}'s data, but is never null. This is a faster way to convert a QByteArray to a QUtf8StringView, if null QByteArrays can legitimately be treated as empty ones. \sa QByteArray::isNull(), QUtf8StringView */