142 lines
4.1 KiB
C++
142 lines
4.1 KiB
C++
/*
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FORMAT-UTIL.hpp - helpers for formatting and diagnostics
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Copyright (C) Lumiera.org
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2009, Hermann Vosseler <Ichthyostega@web.de>
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License as
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published by the Free Software Foundation; either version 2 of
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the License, or (at your option) any later version.
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This program 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
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
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*/
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/** @file format-util.hpp
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** Collection of small helpers and convenience shortcuts for diagnostics & formatting.
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** - util::str() performs a failsafe to-String conversion, thereby preferring a
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** built-in conversion operator, falling back to just a mangled type string.
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** - util::tyStr() generates a string corresponding to the type of the given object.
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** Currently just implemented through the mangled RTTI type string
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**
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** @see FormatHelper_test
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** @see format-string.hpp frontend for boost::format, printf-style
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**
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*/
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#ifndef LIB_FORMAT_UTIL_H
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#define LIB_FORMAT_UTIL_H
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#include "lib/meta/trait.hpp"
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#include "lib/symbol.hpp"
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#include "lib/util.hpp"
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#include <string>
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#include <cstring>
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#include <typeinfo>
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#include <boost/lexical_cast.hpp>
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#include <boost/utility/enable_if.hpp>
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namespace util {
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using boost::enable_if;
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using lib::meta::can_ToString;
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using lib::meta::can_lexical2string;
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using lib::Symbol;
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using util::isnil;
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using std::string;
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namespace { // we need to guard the string conversion
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// to avoid a compiler error in case the type isn't convertible....
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template<typename X>
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struct use_StringConversion : can_ToString<X> { };
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template<typename X>
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struct use_LexicalConversion
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{
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enum { value = can_lexical2string<X>::value
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&& !can_ToString<X>::value
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};
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};
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/** helper: reliably get some string representation for type X */
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template<typename X, typename COND =void>
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struct _InvokeFailsafe
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{
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static string toString (X const&) { return ""; }
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};
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template<typename X>
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struct _InvokeFailsafe<X, typename enable_if< use_StringConversion<X> >::type>
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{
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static string
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toString (X const& val)
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try { return string(val); }
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catch(...) { return ""; }
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};
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template<typename X>
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struct _InvokeFailsafe<X, typename enable_if< use_LexicalConversion<X> >::type>
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{
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static string
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toString (X const& val)
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try { return boost::lexical_cast<string> (val); }
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catch(...) { return ""; }
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};
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}//(End) guards/helpers
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/** @return a string denoting the type. */
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template<typename TY>
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inline string
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tyStr (const TY* =0)
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{
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return string("«")+typeid(TY).name()+"»";
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}
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template<typename TY>
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inline string
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tyStr (TY const& ref)
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{ return tyStr(&ref); }
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/** try to get an object converted to string.
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* A custom/standard conversion to string is used,
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* if applicable; otherwise, some standard types can be
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* converted by a lexical_cast (based on operator<< ).
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* Otherwise, either the fallback string is used, or just
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* a string based on the (mangled) type.
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*/
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template<typename TY>
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inline string
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str ( TY const& val
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, Symbol prefix="" ///< prefix to prepend in case conversion is possible
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, Symbol fallback =0 /// < replacement text to show if string conversion fails
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)
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{
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string res = _InvokeFailsafe<TY>::toString(val);
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if (!isnil (res))
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return string(prefix) + res;
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else
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return fallback? string(fallback)
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: tyStr(val);
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}
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} // namespace util
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#endif
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