321 lines
9 KiB
C++
321 lines
9 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/hash-standard.hpp"
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#include "lib/meta/trait.hpp"
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#include "lib/itertools.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 <sstream>
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#include <cstring>
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#include <utility>
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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 lib {
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namespace test{ // see test-helper.cpp
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std::string demangleCxx (lib::Literal rawName);
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}}
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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::meta::can_IterForEach;
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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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using std::move;
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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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// precision for rendering of double values
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const auto DIAGNOSTICS_DOUBLE_PRECISION = 8;
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const auto DIAGNOSTICS_FLOAT_PRECISION = 5;
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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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/** explicit specialisation to control precision of double values.
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* @note we set an explicit precision, since this is a diagnostic facility
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* and we typically do not want to see all digits, but, for test code,
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* we do want a predictable string representation of simple fractional
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* values like `0.1` (which can not be represented as binary floats)
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*/
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template<>
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struct _InvokeFailsafe<double>
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{
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static string
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toString (double const& val)
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try {
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std::ostringstream buffer;
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buffer.precision(DIAGNOSTICS_DOUBLE_PRECISION);
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buffer << val;
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return buffer.str();
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}
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catch(...) { return ""; }
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};
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template<>
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struct _InvokeFailsafe<float>
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{
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static string
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toString (float const& val)
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try {
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std::ostringstream buffer;
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buffer.precision(DIAGNOSTICS_FLOAT_PRECISION);
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buffer << val;
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return buffer.str();
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}
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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 "«"+ lib::test::demangleCxx (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 { // helper to convert arbitrary elements toString
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template<class CON>
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inline void
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do_stringify(CON&)
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{ /* do nothing */ }
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template<class CON, typename X, typename...ELMS>
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inline void
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do_stringify(CON& container, X const& elm, ELMS const& ...args)
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{
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container += util::str(elm);
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do_stringify (container, args...);
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}
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template<class CON, typename...ELMS>
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struct SeqContainer
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: CON
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{
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void
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operator+= (string&& s)
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{
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CON::push_back (move(s));
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}
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};
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// most common case: use a vector container...
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using std::vector;
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template<typename X, typename...ELMS>
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struct SeqContainer<vector<X>, ELMS...>
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:vector<X>
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{
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SeqContainer()
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{
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this->reserve(sizeof...(ELMS));
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}
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void
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operator+= (string&& s)
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{
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this->emplace_back (move(s));
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}
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};
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}
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/** convert a sequence of elements to string
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* @param elms sequence of arbitrary elements
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* @return a collection of type CON, initialised by the
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* string representation of the given elements
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*/
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template<class CON, typename...ELMS>
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inline CON
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stringify(ELMS const& ...elms)
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{
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SeqContainer<CON,ELMS...> storage;
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do_stringify (storage, elms...);
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return CON {move(storage)};
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}
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namespace { // helper to build range iterator on demand
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template<class CON, typename TOGGLE = void>
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struct _RangeIter
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{
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using StlIter = typename CON::const_iterator;
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lib::RangeIter<StlIter> iter;
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_RangeIter(CON const& collection)
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: iter(begin(collection), end(collection))
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{ }
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};
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template<class IT>
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struct _RangeIter<IT, typename enable_if< can_IterForEach<IT> >::type>
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{
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IT iter;
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_RangeIter(IT&& srcIter)
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: iter(std::forward<IT>(srcIter))
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{ }
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_RangeIter(IT const& srcIter)
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: iter(srcIter)
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{ }
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};
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}
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/**
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* enumerate a collection's contents, separated by delimiter.
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* @param coll something that is standard-iterable
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* @return all contents converted to string and joined into
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* a single string, with separators interspersed.
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* @remarks based on the \c boost::join library function,
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* which in turn is based on
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* additionally, we use our
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* \link #str failsafe string conversion \endlink
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* which in turn invokes custom string conversion,
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* or lexical_cast as appropriate.
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*/
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template<class CON>
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inline string
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join (CON&& coll, string const& delim =", ")
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{
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using Coll = typename lib::meta::Strip<CON>::Type;
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using Val = typename Coll::value_type;
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std::function<string(Val const&)> toString = [] (Val const& val) { return str(val); };
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_RangeIter<Coll> range(std::forward<CON>(coll));
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auto strings = lib::transformIterator(range.iter, toString);
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if (!strings) return "";
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std::ostringstream buffer;
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for (string const& elm : strings)
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buffer << elm << delim;
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// chop off last delimiter
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size_t len = buffer.str().length();
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ASSERT (len > delim.length());
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return buffer.str().substr(0, len - delim.length());
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}
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} // namespace util
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#endif /*LIB_FORMAT_UTIL_H*/
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