parsing.hpp

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// ----------------------------------------------------------------------------
// parsing.hpp :  implementation of the parsing member functions
//                      ( parse, parse_printf_directive)
// ----------------------------------------------------------------------------

//  Copyright Samuel Krempp 2003. Use, modification, and distribution are
//  subject to the Boost Software License, Version 1.0. (See accompanying
//  file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)

// see http://www.boost.org/libs/format for library home page

// ----------------------------------------------------------------------------

#ifndef BOOST_FORMAT_PARSING_HPP
#define BOOST_FORMAT_PARSING_HPP


#include <boost/format/format_class.hpp>
#include <boost/throw_exception.hpp>
#include <boost/assert.hpp>


namespace boost {
namespace io {
namespace detail {

#if defined(BOOST_NO_STD_LOCALE)
    // streams will be used for narrow / widen. but these methods are not const
    template<class T>
    T& const_or_not(const T& x) { 
        return const_cast<T&> (x);
    }
#else
    template<class T>
    const T& const_or_not(const T& x) { 
        return x;
    }
#endif

    template<class Ch, class Facet> inline
    char wrap_narrow(const Facet& fac, Ch c, char deflt) {
        return const_or_not(fac).narrow(c, deflt);
    }

    template<class Ch, class Facet> inline
    bool wrap_isdigit(const Facet& fac, Ch c) {
#if ! defined( BOOST_NO_LOCALE_ISIDIGIT )
        return fac.is(std::ctype<Ch>::digit, c);
# else
        using namespace std;
        return isdigit(c); 
#endif 
    }
 
    template<class Iter, class Facet> 
    Iter wrap_scan_notdigit(const Facet & fac, Iter beg, Iter end) {
        using namespace std;
        for( ; beg!=end && wrap_isdigit(fac, *beg); ++beg) ;
        return beg;
    }


    // Input : [start, last) iterators range and a
    //          a Facet to use its widen/narrow member function
    // Effects : read sequence and convert digits into integral n, of type Res
    // Returns : n
    template<class Res, class Iter, class Facet>
    Iter str2int (const Iter & start, const Iter & last, Res & res, 
                 const Facet& fac) 
    {
        using namespace std;
        Iter it;
        res=0;
        for(it=start; it != last && wrap_isdigit(fac, *it); ++it ) {
            char cur_ch = wrap_narrow(fac, *it, 0); // cant fail.
            res *= 10;
            res += cur_ch - '0'; // 22.2.1.1.2.13 of the C++ standard
        }
        return it;
    }

    // skip printf's "asterisk-fields" directives in the format-string buf
    // Input : char string, with starting index *pos_p
    //         a Facet merely to use its widen/narrow member function
    // Effects : advance *pos_p by skipping printf's asterisk fields.
    // Returns : nothing
    template<class Iter, class Facet>
    Iter skip_asterisk(Iter start, Iter last, const Facet& fac) 
    {
        using namespace std;
        ++ start;
        start = wrap_scan_notdigit(fac, start, last);
        if(start!=last && *start== const_or_not(fac).widen( '$') )
            ++start;
        return start;
    }


    // auxiliary func called by parse_printf_directive
    // for centralising error handling
    // it either throws if user sets the corresponding flag, or does nothing.
    inline void maybe_throw_exception(unsigned char exceptions, 
                                      std::size_t pos, std::size_t size)
    {
        if(exceptions & io::bad_format_string_bit)
            boost::throw_exception(io::bad_format_string(pos, size) );
    }
    

    // Input: the position of a printf-directive in the format-string
    //    a basic_ios& merely to use its widen/narrow member function
    //    a bitset'exceptions' telling whether to throw exceptions on errors.
    // Returns:
    //  true if parse succeeded (ignore some errors if exceptions disabled)
    //  false if it failed so bad that the directive should be printed verbatim
    // Effects:
    //  start is incremented so that *start is the first char after
    //     this directive
    //  *fpar is set with the parameters read in the directive
    template<class Ch, class Tr, class Alloc, class Iter, class Facet>
    bool parse_printf_directive(Iter & start, const Iter& last, 
                                detail::format_item<Ch, Tr, Alloc> * fpar,
                                const Facet& fac,
                                std::size_t offset, unsigned char exceptions)
    {
        typedef typename basic_format<Ch, Tr, Alloc>::format_item_t format_item_t;

        fpar->argN_ = format_item_t::argN_no_posit;  // if no positional-directive
        bool precision_set = false;
        bool in_brackets=false;
        Iter start0 = start;
        std::size_t fstring_size = last-start0+offset;
        if(*start== const_or_not(fac).widen( '|')) {
            in_brackets=true;
            if( ++start >= last ) {
                maybe_throw_exception(exceptions, start-start0 + offset, fstring_size);
                return false;
            }
        }

        // the flag '0' would be picked as a digit for argument order, but here it's a flag :
        if(*start== const_or_not(fac).widen( '0')) 
            goto parse_flags;

        // handle argument order (%2$d)  or possibly width specification: %2d
        if(wrap_isdigit(fac, *start)) {
            int n;
            start = str2int(start, last, n, fac);
            if( start >= last ) {
                maybe_throw_exception(exceptions, start-start0+offset, fstring_size);
                return false;
            }
            
            // %N% case : this is already the end of the directive
            if( *start ==  const_or_not(fac).widen( '%') ) {
                fpar->argN_ = n-1;
                ++start;
                if( in_brackets) 
                    maybe_throw_exception(exceptions, start-start0+offset, fstring_size); 
                // but don't return.  maybe "%" was used in lieu of '$', so we go on.
                else
                    return true;
            }

            if ( *start== const_or_not(fac).widen( '$') ) {
                fpar->argN_ = n-1;
                ++start;
            } 
            else {
                // non-positionnal directive
                fpar->fmtstate_.width_ = n;
                fpar->argN_  = format_item_t::argN_no_posit;
                goto parse_precision;
            }
        }
    
      parse_flags: 
        // handle flags
        while ( start != last) { // as long as char is one of + - = _ # 0 l h   or ' '
            // misc switches
            switch ( wrap_narrow(fac, *start, 0)) {
            case '\'' : break; // no effect yet. (painful to implement)
            case 'l':
            case 'h':  // short/long modifier : for printf-comaptibility (no action needed)
                break;
            case '-':
                fpar->fmtstate_.flags_ |= std::ios_base::left;
                break;
            case '=':
                fpar->pad_scheme_ |= format_item_t::centered;
                break;
            case '_':
                fpar->fmtstate_.flags_ |= std::ios_base::internal;
                break;
            case ' ':
                fpar->pad_scheme_ |= format_item_t::spacepad;
                break;
            case '+':
                fpar->fmtstate_.flags_ |= std::ios_base::showpos;
                break;
            case '0':
                fpar->pad_scheme_ |= format_item_t::zeropad;
                // need to know alignment before really setting flags,
                // so just add 'zeropad' flag for now, it will be processed later.
                break;
            case '#':
                fpar->fmtstate_.flags_ |= std::ios_base::showpoint | std::ios_base::showbase;
                break;
            default:
                goto parse_width;
            }
            ++start;
        } // loop on flag.

        if( start>=last) {
            maybe_throw_exception(exceptions, start-start0+offset, fstring_size);
            return true; 
        }
      parse_width:
        // handle width spec
        // first skip 'asterisk fields' :  *, or *N$
        if(*start == const_or_not(fac).widen( '*') )
            start = skip_asterisk(start, last, fac); 
        if(start!=last && wrap_isdigit(fac, *start))
            start = str2int(start, last, fpar->fmtstate_.width_, fac);

      parse_precision:
        if( start>= last) { 
            maybe_throw_exception(exceptions, start-start0+offset, fstring_size);
            return true;
        }
        // handle precision spec
        if (*start== const_or_not(fac).widen( '.')) {
            ++start;
            if(start != last && *start == const_or_not(fac).widen( '*') )
                start = skip_asterisk(start, last, fac); 
            if(start != last && wrap_isdigit(fac, *start)) {
                start = str2int(start, last, fpar->fmtstate_.precision_, fac);
                precision_set = true;
            }
            else
                fpar->fmtstate_.precision_ =0;
        }
    
        // handle  formatting-type flags :
        while( start != last && ( *start== const_or_not(fac).widen( 'l')