206 lines
6.1 KiB
C++
206 lines
6.1 KiB
C++
/**
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* @file stringize.h
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* @author Nat Goodspeed
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* @date 2008-12-17
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* @brief stringize(item) template function and STRINGIZE(expression) macro
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*
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* $LicenseInfo:firstyear=2008&license=viewerlgpl$
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* Second Life Viewer Source Code
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* Copyright (C) 2010, Linden Research, Inc.
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation;
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* version 2.1 of the License only.
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with this library; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*
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* Linden Research, Inc., 945 Battery Street, San Francisco, CA 94111 USA
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* $/LicenseInfo$
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*/
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#if ! defined(LL_STRINGIZE_H)
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#define LL_STRINGIZE_H
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#include <sstream>
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#include <llstring.h>
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#include <boost/call_traits.hpp>
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/**
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* stream_to(std::ostream&, items, ...) streams each item in the parameter list
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* to the passed std::ostream using the insertion operator <<. This can be
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* used, for instance, to make a simple print() function, e.g.:
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*
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* @code
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* template <typename... Items>
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* void print(Items&&... items)
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* {
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* stream_to(std::cout, std::forward<Items>(items)...);
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* }
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* @endcode
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*/
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// recursion tail
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template <typename CHARTYPE>
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void stream_to(std::basic_ostream<CHARTYPE>& out) {}
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// stream one or more items
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template <typename CHARTYPE, typename T, typename... Items>
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void stream_to(std::basic_ostream<CHARTYPE>& out, T&& item, Items&&... items)
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{
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out << std::forward<T>(item);
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stream_to(out, std::forward<Items>(items)...);
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}
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// why we use function overloads, not function template specializations:
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// http://www.gotw.ca/publications/mill17.htm
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/**
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* gstringize(item, ...) encapsulates an idiom we use constantly, using
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* operator<<(std::ostringstream&, TYPE) followed by std::ostringstream::str()
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* or their wstring equivalents to render a string expressing one or more items.
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*/
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// two or more args - the case of a single argument is handled separately
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template <typename CHARTYPE, typename T0, typename T1, typename... Items>
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auto gstringize(T0&& item0, T1&& item1, Items&&... items)
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{
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std::basic_ostringstream<CHARTYPE> out;
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stream_to(out, std::forward<T0>(item0), std::forward<T1>(item1),
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std::forward<Items>(items)...);
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return out.str();
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}
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// generic single argument: stream to out, as above
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template <typename CHARTYPE, typename T>
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struct gstringize_impl
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{
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auto operator()(typename boost::call_traits<T>::param_type arg)
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{
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std::basic_ostringstream<CHARTYPE> out;
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out << arg;
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return out.str();
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}
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};
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// partially specialize for a single STRING argument -
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// note that ll_convert<T>(T) already handles the trivial case
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template <typename OUTCHAR, typename INCHAR>
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struct gstringize_impl<OUTCHAR, std::basic_string<INCHAR>>
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{
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auto operator()(const std::basic_string<INCHAR>& arg)
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{
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return ll_convert<std::basic_string<OUTCHAR>>(arg);
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}
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};
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// partially specialize for a single CHARTYPE* argument -
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// since it's not a basic_string and we do want to optimize this common case
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template <typename OUTCHAR, typename INCHAR>
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struct gstringize_impl<OUTCHAR, INCHAR*>
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{
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auto operator()(const INCHAR* arg)
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{
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return ll_convert<std::basic_string<OUTCHAR>>(arg);
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}
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};
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// gstringize(single argument)
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template <typename CHARTYPE, typename T>
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auto gstringize(T&& item)
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{
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// use decay<T> so we don't require separate specializations
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// for T, const T, T&, const T& ...
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return gstringize_impl<CHARTYPE, std::decay_t<T>>()(std::forward<T>(item));
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}
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/**
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* Specialization of gstringize for std::string return types
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*/
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template <typename... Items>
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auto stringize(Items&&... items)
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{
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return gstringize<char>(std::forward<Items>(items)...);
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}
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/**
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* Specialization of gstringize for std::wstring return types
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*/
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template <typename... Items>
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auto wstringize(Items&&... items)
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{
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return gstringize<wchar_t>(std::forward<Items>(items)...);
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}
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/**
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* stringize_f(functor)
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*/
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template <typename CHARTYPE, typename Functor>
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std::basic_string<CHARTYPE> stringize_f(Functor const & f)
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{
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std::basic_ostringstream<CHARTYPE> out;
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f(out);
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return out.str();
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}
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/**
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* STRINGIZE(item1 << item2 << item3 ...) effectively expands to the
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* following:
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* @code
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* std::ostringstream out;
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* out << item1 << item2 << item3 ... ;
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* return out.str();
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* @endcode
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*/
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#define STRINGIZE(EXPRESSION) (stringize_f<char>([&](std::ostream& out){ out << EXPRESSION; }))
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/**
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* WSTRINGIZE() is the wstring equivalent of STRINGIZE()
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*/
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#define WSTRINGIZE(EXPRESSION) (stringize_f<wchar_t>([&](std::wostream& out){ out << EXPRESSION; }))
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/**
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* destringize(str)
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* defined for symmetry with stringize
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* @NOTE - this has distinct behavior from boost::lexical_cast<T> regarding
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* leading/trailing whitespace and handling of bad_lexical_cast exceptions
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* @NOTE - no need for dewstringize(), since passing std::wstring will Do The
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* Right Thing
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*/
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template <typename T, typename CHARTYPE>
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T destringize(std::basic_string<CHARTYPE> const & str)
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{
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T val;
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std::basic_istringstream<CHARTYPE> in(str);
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in >> val;
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return val;
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}
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/**
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* destringize_f(str, functor)
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*/
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template <typename CHARTYPE, typename Functor>
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void destringize_f(std::basic_string<CHARTYPE> const & str, Functor const & f)
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{
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std::basic_istringstream<CHARTYPE> in(str);
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f(in);
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}
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/**
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* DESTRINGIZE(str, item1 >> item2 >> item3 ...) effectively expands to the
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* following:
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* @code
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* std::istringstream in(str);
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* in >> item1 >> item2 >> item3 ... ;
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* @endcode
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*/
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#define DESTRINGIZE(STR, EXPRESSION) (destringize_f((STR), [&](auto& in){in >> EXPRESSION;}))
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// legacy name, just use DESTRINGIZE() going forward
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#define DEWSTRINGIZE(STR, EXPRESSION) DESTRINGIZE(STR, EXPRESSION)
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#endif /* ! defined(LL_STRINGIZE_H) */
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