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Diffstat (limited to 'include/rtl/stringconcat.hxx')
| -rw-r--r-- | include/rtl/stringconcat.hxx | 394 |
1 files changed, 394 insertions, 0 deletions
diff --git a/include/rtl/stringconcat.hxx b/include/rtl/stringconcat.hxx new file mode 100644 index 0000000000..0bed28ac81 --- /dev/null +++ b/include/rtl/stringconcat.hxx @@ -0,0 +1,394 @@ +/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */ +/* + * This file is part of the LibreOffice project. + * + * This Source Code Form is subject to the terms of the Mozilla Public + * License, v. 2.0. If a copy of the MPL was not distributed with this + * file, You can obtain one at http://mozilla.org/MPL/2.0/. + */ + +#ifndef INCLUDED_RTL_STRINGCONCAT_HXX +#define INCLUDED_RTL_STRINGCONCAT_HXX + +// This file is only included from LIBO_INTERNAL_ONLY + +#include "rtl/stringutils.hxx" +#include "rtl/string.h" +#include "rtl/ustring.h" + +#include <cassert> +#include <cstddef> +#include <memory> +#include <string> +#include <string_view> +#include <type_traits> +#include <utility> + +#include <string.h> + +#if defined RTL_STRING_UNITTEST_CONCAT +extern bool rtl_string_unittest_invalid_concat; +#endif + +#ifdef RTL_STRING_UNITTEST +#define rtl rtlunittest +#endif +namespace rtl +{ +#ifdef RTL_STRING_UNITTEST +#undef rtl +#endif + +/* +Implementation of efficient string concatenation. + +The whole system is built around two basic template classes: +- ToStringHelper< T > - for each T it can give the length of the resulting string representation and can write + this string representation to a buffer +- O(U)StringConcat< T1, T2 > - operator+ now, instead of creating O(U)String object, returns only this helper object, + that keeps a reference to both operator+ operands; only when converted to O(U)String it will actually create + the resulting string object using ToStringHelper, creating directly the resulting object without any string + intermediate objects +As all the code is inline methods, it allows for extensive optimization and will usually result in very effective code +(even surpassing strlen/strcat and equalling handwritten), while allowing for very easy and intuitive syntax. +*/ + +/** +@internal + +Helper class for converting a given type to a string representation. +*/ +template< typename T > +struct ToStringHelper +{ + /// Return length of the string representation of the given object. + // static std::size_t length( const T& ); + /// Add 8-bit representation of the given object to the given buffer and return position right after the added data. + // char* operator()( char* buffer, const T& ) const SAL_RETURNS_NONNULL; + /// Add Unicode representation of the given object to the given buffer and return position right after the added data. + // sal_Unicode* operator()( sal_Unicode* buffer, const T& ) const SAL_RETURNS_NONNULL; +}; + +/// If true, T can be used in concatenation resulting in O(U)String. +template<typename C, typename T, class Enable = void> constexpr bool allowStringConcat = false; +template<typename C, typename T> constexpr bool allowStringConcat<C, T, std::enable_if_t<std::is_invocable_v<ToStringHelper<T>, C*, T>>> = true; + +template <typename C> inline +C* addDataHelper( C* buffer, const C* data, std::size_t length ) +{ + if (length != 0) { + memcpy( buffer, data, length * sizeof( C )); + } + return buffer + length; +} + +inline +sal_Unicode* addDataLiteral( sal_Unicode* buffer, const char* data, std::size_t length ) +{ + for( std::size_t i = 0; i != length; ++i ) + *buffer++ = *data++; + return buffer; +} + +template <typename C> inline +C* addDataString( C* buffer, const C* str ) +{ + while( *str != '\0' ) + *buffer++ = *str++; + return buffer; +} + +template<> +struct ToStringHelper< const char* > +{ + static std::size_t length( const char* str ) { + return str ? strlen( str ) : 0; + } + char* operator()( char* buffer, const char* str ) const { + return str ? addDataString( buffer, str ) : buffer; + } +}; + +template<> +struct ToStringHelper< char* > : public ToStringHelper< const char* > {}; + +template< std::size_t N > +struct ToStringHelper< char[ N ] > +{ + static std::size_t length( const char str[ N ] ) { + return strlen( str ); + } + char* operator()( char* buffer, const char str[ N ] ) const { return addDataString( buffer, str ); } +}; + +template< std::size_t N > +struct ToStringHelper< const char[ N ] > +{ + static std::size_t length( const char str[ N ] ) { (void)str; assert( strlen( str ) == N - 1 ); return N - 1; } + char* operator()( char* buffer, const char str[ N ] ) const { return addDataHelper( buffer, str, N - 1 ); } + sal_Unicode* operator()( sal_Unicode* buffer, const char str[ N ] ) const { return addDataLiteral( buffer, str, N - 1 ); } +}; + +template<> +struct ToStringHelper<OStringChar> +{ + static std::size_t length(OStringChar) { return 1; } + char* operator()(char* buffer, OStringChar data) const + { return addDataHelper(buffer, &data.c, 1); } +}; + +template<> +struct ToStringHelper< const sal_Unicode* > +{ + static std::size_t length( const sal_Unicode* str ) { + return str ? std::char_traits<char16_t>::length( str ) : 0; + } + sal_Unicode* operator()( sal_Unicode* buffer, const sal_Unicode* str ) const { + return str ? addDataString( buffer, str ) : buffer; + } +}; + +template<> +struct ToStringHelper< sal_Unicode* > : public ToStringHelper< const sal_Unicode* > {}; + +template<std::size_t N> +struct ToStringHelper<sal_Unicode[ N ]> +{ + static std::size_t length( const sal_Unicode str[ N ] ) { + return std::char_traits<char16_t>::length( str ); + } + sal_Unicode * operator()(sal_Unicode * buffer, sal_Unicode const str[N]) const + { return addDataHelper(buffer, str, N - 1); } +}; + +template<std::size_t N> +struct ToStringHelper<sal_Unicode const[N]> +{ + static std::size_t length( const sal_Unicode str[ N ] ) { (void)str; assert( std::char_traits<char16_t>::length( str ) == N - 1 ); return N - 1; } + sal_Unicode * operator()(sal_Unicode * buffer, sal_Unicode const str[N]) const + { return addDataHelper(buffer, str, N - 1); } +}; + +template<> +struct ToStringHelper<OUStringChar_> +{ + static std::size_t length(OUStringChar_) { return 1; } + sal_Unicode * operator()(sal_Unicode * buffer, OUStringChar_ literal) const + { return addDataHelper(buffer, &literal.c, 1); } +}; + +/** +@internal + +Objects returned by operator+, instead of O(U)String. These objects (possibly recursively) keep a representation of the whole +concatenation operation. + +If you get a build error related to this class, you most probably need to explicitly convert the result of a string +concatenation to O(U)String. +*/ +template <typename C, typename T1, typename T2, std::enable_if_t<allowStringConcat<C, T1> && allowStringConcat<C, T2>, int> = 0 > +struct StringConcat +{ +public: + StringConcat( const T1& left_, const T2& right_ ) : left( left_ ), right( right_ ) {} + std::size_t length() const { return ToStringHelper< T1 >::length( left ) + ToStringHelper< T2 >::length( right ); } + C* addData( C* buffer ) const SAL_RETURNS_NONNULL { return ToStringHelper< T2 >()( ToStringHelper< T1 >()( buffer, left ), right ); } + // NOTE here could be functions that would forward to the "real" temporary O(U)String. Note however that e.g. getStr() + // is not so simple, as the O(U)String temporary must live long enough (i.e. can't be created here in a function, a wrapper + // temporary object containing it must be returned instead). +private: + const T1& left; + const T2& right; +}; + +template <typename C, typename T1, typename T2> struct ToStringHelper<StringConcat<C, T1, T2>> +{ + static std::size_t length(const StringConcat<C, T1, T2 >& c) { return c.length(); } + C* operator()(C* buffer, const StringConcat<C, T1, T2>& c) const SAL_RETURNS_NONNULL { return c.addData(buffer); } +}; + +template <typename T1, typename T2> using OStringConcat = StringConcat<char, T1, T2>; +template <typename T1, typename T2> using OUStringConcat = StringConcat<sal_Unicode, T1, T2>; + +template< typename T1, typename T2 > +[[nodiscard]] +inline +OStringConcat< T1, T2 > operator+( const T1& left, const T2& right ) +{ + return OStringConcat< T1, T2 >( left, right ); +} + +// char[N] and const char[N] need to be done explicitly, otherwise the compiler likes to treat them the same way for some reason +template< typename T, std::size_t N > +[[nodiscard]] +inline +OStringConcat< T, const char[ N ] > operator+( const T& left, const char (&right)[ N ] ) +{ + return OStringConcat< T, const char[ N ] >( left, right ); +} + +template< typename T, std::size_t N > +[[nodiscard]] +inline +OStringConcat< const char[ N ], T > operator+( const char (&left)[ N ], const T& right ) +{ + return OStringConcat< const char[ N ], T >( left, right ); +} + +template< typename T, std::size_t N > +[[nodiscard]] +inline +OStringConcat< T, char[ N ] > operator+( const T& left, char (&right)[ N ] ) +{ + return OStringConcat< T, char[ N ] >( left, right ); +} + +template< typename T, std::size_t N > +[[nodiscard]] +inline +OStringConcat< char[ N ], T > operator+( char (&left)[ N ], const T& right ) +{ + return OStringConcat< char[ N ], T >( left, right ); +} + +template< typename T1, typename T2 > +[[nodiscard]] +inline +OUStringConcat< T1, T2 > operator+( const T1& left, const T2& right ) +{ + return OUStringConcat< T1, T2 >( left, right ); +} + +template< typename T1, typename T2 > +[[nodiscard]] +inline +typename std::enable_if_t< libreoffice_internal::ConstCharArrayDetector< T1, void >::ok, OUStringConcat< T1, T2 > > operator+( T1& left, const T2& right ) +{ + return OUStringConcat< T1, T2 >( left, right ); +} + +template< typename T1, typename T2 > +[[nodiscard]] +inline +typename std::enable_if_t< libreoffice_internal::ConstCharArrayDetector< T2, void >::ok, OUStringConcat< T1, T2 > > operator+( const T1& left, T2& right ) +{ + return OUStringConcat< T1, T2 >( left, right ); +} + +#ifdef RTL_STRING_UNITTEST_CONCAT +// Special overload to catch the remaining invalid combinations. The helper struct must +// be used to make this operator+ overload a worse choice than all the existing overloads above. +struct StringConcatInvalid + { + template< typename T > + StringConcatInvalid( const T& ) {} + }; +template< typename T > +inline +int operator+( const StringConcatInvalid&, const T& ) + { + rtl_string_unittest_invalid_concat = true; + return 0; // doesn't matter + } +#endif + +// Lightweight alternative to O(U)String when a (temporary) object is needed to hold +// an O(U)StringConcat result that can then be used as a std::(u16)string_view: +template <typename C> class StringConcatenation { +public: + template <class Concat> + explicit StringConcatenation(Concat const& c): + length_(c.length()), + buffer_(new C[length_]) + { + auto const end = c.addData(buffer_.get()); + assert(end == buffer_.get() + length_); (void)end; + } + + operator std::basic_string_view<C>() const { return {buffer_.get(), length_}; } + +private: + std::size_t length_; + std::unique_ptr<C[]> buffer_; +}; + +template <typename C, typename T1, typename T2> auto Concat2View(StringConcat<C, T1, T2> const& c) +{ + return StringConcatenation<C>(c); +} + +/** +* O(U)StringNumber implementation + +Objects returned by O(U)String::number(), instead of O(U)String. These objects keep a representation of the number() operation. + +If you get a build error related to this class, you most probably need to explicitly convert the result of calling +O(U)String::number() to O(U)String. +*/ + +template <typename C, std::size_t nBufSize> struct StringNumber +{ + template <typename Func, typename... Args, + std::enable_if_t<std::is_invocable_r_v<sal_Int32, Func, C*, Args...>, int> = 0> + StringNumber(Func func, Args... args) { length = func(buf, args...); } + // O(U)String::number(value).getStr() is very common (writing xml code, ...), + // so implement that one also here, to avoid having to explicitly convert + // to O(U)String in all such places + const C* getStr() const SAL_RETURNS_NONNULL { return buf; } + StringNumber&& toAsciiUpperCase() && + { + if constexpr (sizeof(C) == sizeof(char)) + rtl_str_toAsciiUpperCase_WithLength(buf, length); + else + rtl_ustr_toAsciiUpperCase_WithLength(buf, length); + return std::move(*this); + } + operator std::basic_string_view<C>() const { return std::basic_string_view<C>(buf, length); } + C buf[nBufSize]; + sal_Int32 length; +}; + +template<std::size_t nBufSize> using OStringNumber = StringNumber<char, nBufSize>; +template<std::size_t nBufSize> using OUStringNumber = StringNumber<sal_Unicode, nBufSize>; + +template< typename C, std::size_t nBufSize > +struct ToStringHelper< StringNumber< C, nBufSize > > +{ + static std::size_t length( const StringNumber< C, nBufSize >& n ) { return n.length; } + C* operator()( C* buffer, const StringNumber< C, nBufSize >& n ) const SAL_RETURNS_NONNULL { return addDataHelper( buffer, n.buf, n.length ); } +}; + +template<typename C> struct ToStringHelper<std::basic_string_view<C>> { + static constexpr std::size_t length(std::basic_string_view<C> s) { return s.size(); } + + C * operator()(C * buffer, std::basic_string_view<C> s) const SAL_RETURNS_NONNULL + { return addDataHelper(buffer, s.data(), s.size()); } +}; + +// An internal marker class used by O(U)String::Concat: +template<typename C> struct StringConcatMarker {}; + +using OStringConcatMarker = StringConcatMarker<char>; +using OUStringConcatMarker = StringConcatMarker<sal_Unicode>; + +template<typename C> constexpr bool allowStringConcat<C, StringConcatMarker<C>> = true; + +#if defined __GNUC__ && !defined __clang__ +template <typename C, typename T2> +struct StringConcat<C, StringConcatMarker<C>, T2> +#else +template <typename C, typename T2, std::enable_if_t<allowStringConcat<C, T2>, int> Dummy> +struct StringConcat<C, StringConcatMarker<C>, T2, Dummy> +#endif +{ +public: + StringConcat( const T2& right_ ) : right( right_ ) {} + std::size_t length() const { return ToStringHelper< T2 >::length( right ); } + C* addData( C* buffer ) const SAL_RETURNS_NONNULL { return ToStringHelper< T2 >()( buffer, right ); } +private: + const T2& right; +}; + +} // namespace + +#endif |