assimp/include/assimp/TinyFormatter.h

/*
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*/

/** @file  TinyFormatter.h
 *  @brief Utility to format log messages more easily. Introduced
 *    to get rid of the boost::format dependency. Much slinker,
 *    basically just extends stringstream.
 */
#pragma once
#ifndef INCLUDED_TINY_FORMATTER_H
#define INCLUDED_TINY_FORMATTER_H

#ifdef __GNUC__
#   pragma GCC system_header
#endif

#include <sstream>

namespace Assimp {
namespace Formatter {

// ------------------------------------------------------------------------------------------------
/** stringstream utility. Usage:
 *  @code
 *  void writelog(const std::string&s);
 *  void writelog(const std::wstring&s);
 *  ...
 *  writelog(format()<< "hi! this is a number: " << 4);
 *  writelog(wformat()<< L"hi! this is a number: " << 4);
 *
 *  @endcode */
template < typename T,
    typename CharTraits = std::char_traits<T>,
    typename Allocator  = std::allocator<T> >
class basic_formatter {
public:
    typedef class std::basic_string<T,CharTraits,Allocator> string;
    typedef class std::basic_ostringstream<T,CharTraits,Allocator> stringstream;

    basic_formatter() {
        // empty
    }

    /* Allow basic_formatter<T>'s to be used almost interchangeably
     * with std::(w)string or const (w)char* arguments because the
     * conversion c'tor is called implicitly. */
    template <typename TT>
    basic_formatter(const TT& sin)  {
        underlying << sin;
    }

    // Same problem as the copy constructor below, but with root cause is that stream move
    // is not permitted on older GCC versions. Small performance impact on those platforms.
#if defined(__GNUC__) && (__GNUC__ == 4 && __GNUC_MINOR__ <= 9)
    basic_formatter(basic_formatter&& other) {
        underlying << (string)other;
    }
#else
    basic_formatter(basic_formatter&& other)
        : underlying(std::move(other.underlying)) {
    }
#endif

    // The problem described here:
    // https://sourceforge.net/tracker/?func=detail&atid=1067632&aid=3358562&group_id=226462
    // can also cause trouble here. Apparently, older gcc versions sometimes copy temporaries
    // being bound to const ref& function parameters. Copying streams is not permitted, though.
    // This workaround avoids this by manually specifying a copy ctor.
#if !defined(__GNUC__) || !defined(__APPLE__) || __GNUC__ > 4 || (__GNUC__ == 4 && __GNUC_MINOR__ >= 6)
    explicit basic_formatter(const basic_formatter& other) {
        underlying << (string)other;
    }
#endif

    operator string () const {
        return underlying.str();
    }

    /* note - this is declared const because binding temporaries does only
     * work for const references, so many function prototypes will
     * include const basic_formatter<T>& s but might still want to
     * modify the formatted string without the need for a full copy.*/
    template <typename TToken, typename std::enable_if<!std::is_base_of<std::exception, TToken>::value>::type * = nullptr>
    const basic_formatter &operator<<(const TToken &s) const {
        underlying << s;
        return *this;
    }

    template <typename TToken, typename std::enable_if<std::is_base_of<std::exception, TToken>::value>::type * = nullptr>
    const basic_formatter &operator<<(const TToken &s) const {
        underlying << s.what();
        return *this;
    }

    template <typename TToken, typename std::enable_if<!std::is_base_of<std::exception, TToken>::value>::type * = nullptr>
    basic_formatter &operator<<(const TToken &s) {
        underlying << s;
        return *this;
    }

    template <typename TToken, typename std::enable_if<std::is_base_of<std::exception, TToken>::value>::type * = nullptr>
    basic_formatter &operator<<(const TToken &s) {
        underlying << s.what();
        return *this;
    }


    // comma operator overloaded as well, choose your preferred way.
    template <typename TToken>
    const basic_formatter& operator, (const TToken& s) const {
        *this << s;
        return *this;
    }

    template <typename TToken>
    basic_formatter& operator, (const TToken& s) {
        *this << s;
        return *this;
    }

    // Fix for MSVC8
    // See https://sourceforge.net/projects/assimp/forums/forum/817654/topic/4372824
    template <typename TToken>
    basic_formatter& operator, (TToken& s) {
        *this << s;
        return *this;
    }


private:
    mutable stringstream underlying;
};


typedef basic_formatter< char > format;
typedef basic_formatter< wchar_t > wformat;

} // ! namespace Formatter

} // ! namespace Assimp

#endif