lix/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 R<>diger 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/throw_exception.hpp"

namespace boost {
namespace io {
namespace detail {
namespace  { 

  template<class Tr, class Ch> inline
  void empty_buf(BOOST_IO_STD basic_ostringstream<Ch,Tr> & os) { 
    static const std::basic_string<Ch, Tr> emptyStr;
    os.str(emptyStr); 
  }

  template<class Ch, class Tr>
  void do_pad( std::basic_string<Ch,Tr> & s, 
                std::streamsize w, 
                const Ch c, 
                std::ios_base::fmtflags f, 
                bool center) 
    // applies centered / left / right  padding  to the string s.
    // Effects : string s is padded.
  {
    std::streamsize n=w-s.size();
    if(n<=0) {
      return;
    }
    if(center) 
      {
        s.reserve(w); // allocate once for the 2 inserts
        const std::streamsize n1 = n /2, n0 = n - n1; 
        s.insert(s.begin(), n0, c);
        s.append(n1, c);
      } 
    else 
      {
        if(f & std::ios_base::left) {
          s.append(n, c);
        }
        else {
          s.insert(s.begin(), n, c);
        }
      }
  } // -do_pad(..) 


  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



  
template< class Ch, class Tr, class T> 
void put( T x, 
          const format_item<Ch, Tr>& specs, 
          std::basic_string<Ch, Tr> & res, 
          BOOST_IO_STD basic_ostringstream<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;

  stream_format_state<Ch, Tr>   prev_state(oss_);
    
  specs.state_.apply_on(oss_);

  // in case x is a group, apply the manip part of it, 
  // in order to find width
  put_head( oss_, x );
  empty_buf( oss_);

  const std::streamsize w=oss_.width();
  const std::ios_base::fmtflags fl=oss_.flags();
  const bool internal = (fl & std::ios_base::internal) != 0;
  const bool two_stepped_padding = internal
    &&  ! ( specs.pad_scheme_ & format_item_t::spacepad ) 
    && specs.truncate_ < 0 ;
      

  if(! two_stepped_padding) 
    {
      if(w>0) // handle simple padding via do_pad, not natively in stream 
        oss_.width(0);
      put_last( oss_, x);
      res = oss_.str();

      if (specs.truncate_ >= 0)
        res.erase(specs.truncate_);

      // complex pads :
      if(specs.pad_scheme_ & format_item_t::spacepad)
        {
          if( res.size()==0 ||   ( res[0]!='+' && res[0]!='-'  ))
            {
              res.insert(res.begin(), 1, ' '); // insert 1 space at  pos 0
            }
        }
      if(w > 0) // need do_pad
        {
          do_pad(res,w,oss_.fill(), fl, (specs.pad_scheme_ & format_item_t::centered) !=0 );
        }
    } 
  else  // 2-stepped padding
    {
      put_last( oss_, x); // oss_.width() may result in padding.
      res = oss_.str();
      
      if (specs.truncate_ >= 0)
        res.erase(specs.truncate_);

      if( res.size() - w > 0)
        { //   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.
          empty_buf( oss_);
          oss_.width(0);
          put_last(oss_, x );
          string_t tmp = oss_.str();  // minimal-length output
          std::streamsize d;
          if( (d=w - tmp.size()) <=0 ) 
            {
              // minimal length is already >= w, so no padding  (cool!)
              res.swap(tmp);
            }
          else
            { // hum..  we need to pad (it was necessarily multi-output)
              typedef typename string_t::size_type size_type;
              size_type i = 0;
              while( i<tmp.size() && tmp[i] == res[i] ) // find where we should pad.
                ++i;
              tmp.insert(i, static_cast<size_type>( d ), oss_.fill());
              res.swap( tmp );
            }
        }
      else 
        { // okay, only one thing was printed and padded, so res is fine.
        }
    }

  prev_state.apply_on(oss_);
  empty_buf( oss_);
  oss_.clear();
} // 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 have been 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_;
    }

  // this arg is finished, reset the stream's format state
  self.state0_.apply_on(self.oss_);
  return self;
}
    

} // namespace detail
} // namespace io
} // namespace boost


#endif //  BOOST_FORMAT_FEED_ARGS_HPP