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boost/format/feed_args.hpp

// -*- C++ -*-
//  Boost general library 'format'   ---------------------------
//  See http://www.boost.org for updates, documentation, and revision history.

//  (C) Samuel Krempp 2001
//                  krempp@crans.ens-cachan.fr
//  Permission to copy, use, modify, sell and
//  distribute this software is granted provided this copyright notice appears
//  in all copies. This software is provided "as is" without express or implied
//  warranty, and with no claim as to its suitability for any purpose.

// ideas taken from Rüdiger Loos's format class
// and Karl Nelson's ofstream

// ----------------------------------------------------------------------------
// feed_args.hpp :  functions for processing each argument 
//                      (feed, feed_manip, and distribute)
// ----------------------------------------------------------------------------


#ifndef BOOST_FORMAT_FEED_ARGS_HPP
#define BOOST_FORMAT_FEED_ARGS_HPP

#include <boost/format/format_class.hpp>
#include <boost/format/group.hpp>

#include <boost/format/detail/msvc_disambiguater.hpp>
#include <boost/throw_exception.hpp>

namespace boost {
namespace io {
namespace detail {
namespace  { 

    template<class Ch, class Tr> 
    void clear_buffer(io::basic_outsstream<Ch,Tr> & os) { 
        os.clear_buffer();
    }

    template<class Ch, class Tr>
    void mk_str( std::basic_string<Ch,Tr> & res, 
                 const Ch * beg,
                 std::streamsize size,
                 std::streamsize w, 
                 const Ch fill_char,
                 std::ios_base::fmtflags f, 
                 const Ch prefix_space, // 0 if no space-padding
                 bool center) 
        // applies centered / left / right  padding  to the string  [beg, beg+size[
        // Effects : the result is placed in res.
    {
        res.resize(0);
        std::streamsize n=w-size-!!prefix_space;
        std::streamsize n_after = 0, n_before = 0; 

        if(n<=0) { // no need to pad.
            res.reserve(size + !!prefix_space);
        }
        else { 
            res.reserve(w); // allocate once for the 2 inserts
            if(center) 
                n_after = n/2, n_before = n - n_after; 
            else 
                if(f & std::ios_base::left)
                    n_after = n;
                else
                    n_before = n;
        }
        // now make the res string :
        if(n_before) res.append(n_before, fill_char);
        if(prefix_space) 
            res.append(1, prefix_space);
        res.append(beg, size);
        if(n_after) res.append(n_after, fill_char);
    } // -mk_str(..) 


#if BOOST_WORKAROUND( BOOST_MSVC, <= 1300) 
// MSVC needs to be tricked to disambiguate this simple overload..
// the trick is in "boost/format/msvc_disambiguater.hpp"
  
    template< class Ch, class Tr, class T> inline
    void put_head( BOOST_IO_STD basic_ostream<Ch, Tr>& os, const T& x ) {
        disambiguater<Ch, Tr, T>::put_head(os, x, 1L);
    }
    template< class Ch, class Tr, class T> inline
    void put_last( BOOST_IO_STD basic_ostream<Ch, Tr>& os, const T& x ) {
        disambiguater<Ch, Tr, T>::put_last(os, x, 1L);
    }

#else  

    template< class Ch, class Tr, class T> inline
    void put_head(BOOST_IO_STD basic_ostream<Ch, Tr>& , const T& ) {
    }

    template< class Ch, class Tr, class T> inline
    void put_head( BOOST_IO_STD basic_ostream<Ch, Tr>& os, const group1<T>& x ) {
        os << group_head(x.a1_); // send the first N-1 items, not the last
    }

    template< class Ch, class Tr, class T> inline
    void put_last( BOOST_IO_STD basic_ostream<Ch, Tr>& os, const T& x ) {
        os << x ;
    }

    template< class Ch, class Tr, class T> inline
    void put_last( BOOST_IO_STD basic_ostream<Ch, Tr>& os, const group1<T>& x ) {
        os << group_last(x.a1_); // this selects the last element
    }

#ifndef BOOST_NO_OVERLOAD_FOR_NON_CONST 
    template< class Ch, class Tr, class T> inline
    void put_head( BOOST_IO_STD basic_ostream<Ch, Tr>& , T& ) {
    }

    template< class Ch, class Tr, class T> inline
    void put_last( BOOST_IO_STD basic_ostream<Ch, Tr>& os, T& x ) {
        os << x ;
    }
#endif
#endif  // -msvc workaround


    template< class Ch, class Tr, class T> 
    void put( T x, 
              const format_item<Ch, Tr>& specs, 
              std::basic_string<Ch, Tr> & res, 
              io::basic_outsstream<Ch, Tr>& oss_ ) 
    {
        // does the actual conversion of x, with given params, into a string
        // using the *supplied* strinstream. (the stream state is important)

        typedef std::basic_string<Ch, Tr> string_t;
        typedef format_item<Ch, Tr>  format_item_t;
    
        specs.fmtstate_.apply_on(oss_);

        // the stream format state can be modified by manipulators in the argument :
        put_head( oss_, x );
        // in case x is a group, apply the manip part of it, 
        // in order to find width
        // clear_buffer( oss_); // fixme. is it necessary ?

        const std::ios_base::fmtflags fl=oss_.flags();
        const bool internal = (fl & std::ios_base::internal) != 0;
        const std::streamsize w = oss_.width();
        const bool two_stepped_padding= internal && (w!=0);
      
        res.resize(0);
        if(! two_stepped_padding) {
            if(w>0) // handle padding via mk_str, not natively in stream 
                oss_.width(0);
            put_last( oss_, x);
            const Ch * res_beg = oss_.begin();
            Ch prefix_space = 0;
            if(specs.pad_scheme_ & format_item_t::spacepad)
                if(oss_.pcount()== 0 || 
                   (res_beg[0] !=oss_.widen('+') && res_beg[0] !=oss_.widen('-')  ))
                    prefix_space = oss_.widen(' ');
            std::streamsize res_size = std::min(
              static_cast<std::streamsize>(specs.truncate_ - !!prefix_space),
              oss_.pcount());

            mk_str(res, res_beg, res_size, w, oss_.fill(), fl, 
                   prefix_space, (specs.pad_scheme_ & format_item_t::centered) !=0 );
        } 
        else  { // 2-stepped padding
            // internal can be implied by zeropad, or user-set.
            // left, right, and centered alignment overrule internal,
            // but spacepad or truncate might be mixed with internal (using manipulator)
            put_last( oss_, x); // may pad
            const Ch * res_beg = oss_.begin();
            std::streamsize res_size = oss_.pcount();
            bool prefix_space=false;
            if(specs.pad_scheme_ & format_item_t::spacepad)
                if(oss_.pcount()== 0 || 
                   (res_beg[0] !=oss_.widen('+') && res_beg[0] !=oss_.widen('-')  ))
                    prefix_space = true;
            if(res_size == w && w<=specs.truncate_ && !prefix_space) {
                // okay, only one thing was printed and padded, so res is fine
                res.assign(res_beg, res_size);
            }
            else { //   length w exceeded
                // either it was multi-output with first output padding up all width..
                // either it was one big arg and we are fine.
                //BOOST_ASSERT(res_size > w); //res_size<w means buggy user-defined formatting
                res.assign(res_beg, res_size);
                res_beg=NULL;  // invalidate pointers.
                clear_buffer( oss_);
                oss_.width(0);
                if(prefix_space)
                    oss_ << ' ';
                put_last(oss_, x );
                if(oss_.pcount()==0 && specs.pad_scheme_ & format_item_t::spacepad) {
                    prefix_space =true;
                    oss_ << ' ';
                }
                // minimal-length output
                const Ch * tmp_beg = oss_.begin();
                std::streamsize tmp_size = std::min(oss_.pcount(),
                  static_cast<std::streamsize>(specs.truncate_));
                std::streamsize d;
                if( (d=w - tmp_size) <=0 ) { 
                    // minimal length is already >= w, so no padding (cool!)
                        res.assign(tmp_beg, tmp_size);
                }
                else { // hum..  we need to pad (multi_output, or spacepad present)
                    typedef typename string_t::size_type size_type;
                    std::streamsize i = prefix_space;
                    //find where we should pad
                    //BOOST_ASSERT( static_cast<size_t>(tmp_size-prefix_space <= res.size() ));
                    std::streamsize sz = std::min(res_size+prefix_space, tmp_size);
                    for(; i<sz && tmp_beg[i] == res[i-prefix_space]; ++i){}
                    if(i>=tmp_size) i=prefix_space;
                    res.assign(tmp_beg, i);
                    if(d>0) res.append(static_cast<size_type>( d ), oss_.fill());
                    res.append(tmp_beg+i, tmp_size-i);
                    assert(i+(tmp_size-i)+std::max(d,(std::streamsize)0) == w);
                    assert(res.size() == (std::size_t)w);
                }
            }
        }
        clear_buffer( oss_);
    } // end- put(..)


}  // local namespace


    template< class Ch, class Tr, class T> 
    void distribute(basic_format<Ch,Tr>& self, T x) {
        // call put(x, ..) on every occurence of the current argument :
        if(self.cur_arg_ >= self.num_args_)  {
            if( self.exceptions() & too_many_args_bit )
                boost::throw_exception(too_many_args()); // too many variables supplied
            else return;
        }
        for(unsigned long i=0; i < self.items_.size(); ++i) {
            if(self.items_[i].argN_ == self.cur_arg_) {
                put<Ch, Tr, T> (x, self.items_[i], self.items_[i].res_, self.oss_ );
            }
        }
    }

    template<class Ch, class Tr, class T> 
    basic_format<Ch, Tr>&  feed(basic_format<Ch,Tr>& self, T x) {
        if(self.dumped_) self.clear();
        distribute<Ch, Tr, T> (self, x);
        ++self.cur_arg_;
        if(self.bound_.size() != 0) {
                while( self.cur_arg_ < self.num_args_ && self.bound_[self.cur_arg_] )
                    ++self.cur_arg_;
        }
        return self;
    }
    
} // namespace detail
} // namespace io
} // namespace boost


#endif //  BOOST_FORMAT_FEED_ARGS_HPP