117 lines
4.8 KiB
C++
117 lines
4.8 KiB
C++
// char_conv.hh
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// This file is part of libpbe; see http://anyterm.org/
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// (C) 2008 Philip Endecott
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// Distributed under the Boost Software License, Version 1.0:
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//
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// Permission is hereby granted, free of charge, to any person or organization
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// obtaining a copy of the software and accompanying documentation covered by
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// this license (the "Software") to use, reproduce, display, distribute,
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// execute, and transmit the Software, and to prepare derivative works of the
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// Software, and to permit third-parties to whom the Software is furnished to
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// do so, all subject to the following:
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//
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// The copyright notices in the Software and this entire statement, including
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// the above license grant, this restriction and the following disclaimer,
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// must be included in all copies of the Software, in whole or in part, and
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// all derivative works of the Software, unless such copies or derivative
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// works are solely in the form of machine-executable object code generated by
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// a source language processor.
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//
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// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
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// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
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// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
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// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
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// DEALINGS IN THE SOFTWARE.
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#ifndef libpbe_charset_char_conv_hh
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#define libpbe_charset_char_conv_hh
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#include "charset_t.hh"
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#include "charset_traits.hh"
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#include "error_policy.hh"
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#include <boost/static_assert.hpp>
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#include "compiler_magic.hh"
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namespace pbe {
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// Conversion of characters between character sets
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// -----------------------------------------------
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//
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// This file provides facilities to convert a single character from
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// one character set to another. It's implemented using specialisations
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// for character set pairs in other files.
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// A template parameter specifies a policy for error handling.
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// Because function templates can't be partially specialised, and
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// the character-set-pair specialisation will not want to be specialised
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// on the error handling polocy, we need to wrap the conversion in a
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// class.
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// The default implementation here converts to a UCS4 character as an
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// intermediate step, which will work as long as the necessary supporting
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// conversions are implemented somehow.
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// There's also a specialisation here for the null conversion where source
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// and destination are the same.
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// Base template, with default implementation via ucs4:
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template <charset_t from_cs, charset_t to_cs, typename error_policy>
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struct char_conv {
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// We shouldn't be here if from_cs or to_cs is ucs4; that indicates recursion.
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// A specialisation should have been invoked. Maybe the appropriate
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// specialisation hasn't been #included, or hasn't been written?
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BOOST_STATIC_ASSERT(from_cs!=cs::ucs4 && to_cs!=cs::ucs4);
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// FIXME shouldn't this be a static member function?
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typename charset_traits<to_cs>::char_t
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operator() ( typename charset_traits<from_cs>::char_t c,
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typename charset_traits<from_cs>::state_t& from_state
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= charset_traits<from_cs>::state_t(),
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typename charset_traits<to_cs>::state_t& to_state
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= charset_traits<to_cs>::state_t() )
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{
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charset_traits<cs::ucs4>::state_t ucs4_state;
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char32_t tmp = char_conv<from_cs, cs::ucs4, error_policy>() (c,from_state,ucs4_state);
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return char_conv<cs::ucs4, to_cs, error_policy>() (tmp,ucs4_state,to_state);
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}
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};
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// Specialisation for trivial conversion to the same character set:
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template <charset_t cset, typename error_policy>
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struct char_conv<cset,cset,error_policy> {
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typename charset_traits<cset>::char_t
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operator() ( typename charset_traits<cset>::char_t c,
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PBE_UNUSED_ARG(typename charset_traits<cset>::state_t& from_state)
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= charset_traits<cset>::state_t(),
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PBE_UNUSED_ARG(typename charset_traits<cset>::state_t& to_state)
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= charset_traits<cset>::state_t() )
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{
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return c;
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}
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};
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// This macro is used elsewhere to define trivial conversions.
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#define IDENTITY_CHAR_CONV(FROM_CS,TO_CS) \
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template <typename error_policy> \
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struct char_conv<FROM_CS,TO_CS,error_policy> { \
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charset_traits<TO_CS>::char_t \
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operator() ( charset_traits<FROM_CS>::char_t c, \
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charset_traits<FROM_CS>::state_t&, \
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charset_traits<TO_CS>::state_t& ) { \
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return static_cast<unsigned charset_traits<FROM_CS>::char_t>(c); \
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} \
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};
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};
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#endif
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