49 lines
1.4 KiB
C++
49 lines
1.4 KiB
C++
// Copyright (c) 2014-2016 Dr. Colin Hirsch and Daniel Frey
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// Please see LICENSE for license or visit https://github.com/ColinH/PEGTL/
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#ifndef TAO_CPP_PEGTL_INTERNAL_PEEK_UTF16_HH
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#define TAO_CPP_PEGTL_INTERNAL_PEEK_UTF16_HH
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#include <type_traits>
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#include "input_pair.hh"
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namespace tao_json_pegtl
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{
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namespace internal
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{
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struct peek_utf16
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{
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using data_t = char32_t;
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using pair_t = input_pair< char32_t >;
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using short_t = std::make_unsigned< char16_t >::type;
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static_assert( sizeof( short_t ) == 2, "expected size 2 for 16bit value" );
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static_assert( sizeof( char16_t ) == 2, "expected size 2 for 16bit value" );
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template< typename Input >
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static pair_t peek( Input & in )
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{
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const std::size_t s = in.size( 4 );
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if ( s >= 2 ) {
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const char32_t t = * reinterpret_cast< const short_t * >( in.begin() );
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if ( ( t < 0xd800 ) || ( t > 0xdbff ) || ( s < 4 ) ) {
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return { t, 2 };
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}
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const char32_t u = * reinterpret_cast< const short_t * >( in.begin() + 2 );
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if ( ( u < 0xdc00 ) || ( u > 0xdfff ) ) {
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return { t, 2 };
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}
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return { ( ( ( t & 0x03ff ) << 10 ) | ( u & 0x03ff ) ) + 0x10000, 4 };
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}
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return { 0, 0 };
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}
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};
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} // namespace internal
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} // namespace tao_json_pegtl
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#endif
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