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90 lines
2.8 KiB
C++
90 lines
2.8 KiB
C++
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// Copyright (c) 2014-2022 Dr. Colin Hirsch and Daniel Frey
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// Please see LICENSE for license or visit https://github.com/taocpp/PEGTL/
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#ifndef TAO_PEGTL_INTERNAL_PEEK_UTF8_HPP
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#define TAO_PEGTL_INTERNAL_PEEK_UTF8_HPP
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#include "../config.hpp"
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#include "input_pair.hpp"
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namespace TAO_PEGTL_NAMESPACE::internal
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{
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struct peek_utf8
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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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template< typename ParseInput >
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[[nodiscard]] static pair_t peek( ParseInput& in ) noexcept( noexcept( in.empty() ) )
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{
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if( in.empty() ) {
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return { 0, 0 };
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}
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const char32_t c0 = in.peek_uint8();
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if( ( c0 & 0x80 ) == 0 ) {
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return { c0, 1 };
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}
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return peek_impl( in, c0 );
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}
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private:
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template< typename ParseInput >
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[[nodiscard]] static pair_t peek_impl( ParseInput& in, char32_t c0 ) noexcept( noexcept( in.size( 4 ) ) )
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{
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if( ( c0 & 0xE0 ) == 0xC0 ) {
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if( in.size( 2 ) >= 2 ) {
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const char32_t c1 = in.peek_uint8( 1 );
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if( ( c1 & 0xC0 ) == 0x80 ) {
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c0 &= 0x1F;
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c0 <<= 6;
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c0 |= ( c1 & 0x3F );
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if( c0 >= 0x80 ) {
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return { c0, 2 };
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}
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}
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}
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}
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else if( ( c0 & 0xF0 ) == 0xE0 ) {
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if( in.size( 3 ) >= 3 ) {
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const char32_t c1 = in.peek_uint8( 1 );
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const char32_t c2 = in.peek_uint8( 2 );
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if( ( ( c1 & 0xC0 ) == 0x80 ) && ( ( c2 & 0xC0 ) == 0x80 ) ) {
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c0 &= 0x0F;
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c0 <<= 6;
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c0 |= ( c1 & 0x3F );
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c0 <<= 6;
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c0 |= ( c2 & 0x3F );
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if( c0 >= 0x800 && !( c0 >= 0xD800 && c0 <= 0xDFFF ) ) {
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return { c0, 3 };
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}
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}
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}
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}
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else if( ( c0 & 0xF8 ) == 0xF0 ) {
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if( in.size( 4 ) >= 4 ) {
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const char32_t c1 = in.peek_uint8( 1 );
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const char32_t c2 = in.peek_uint8( 2 );
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const char32_t c3 = in.peek_uint8( 3 );
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if( ( ( c1 & 0xC0 ) == 0x80 ) && ( ( c2 & 0xC0 ) == 0x80 ) && ( ( c3 & 0xC0 ) == 0x80 ) ) {
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c0 &= 0x07;
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c0 <<= 6;
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c0 |= ( c1 & 0x3F );
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c0 <<= 6;
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c0 |= ( c2 & 0x3F );
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c0 <<= 6;
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c0 |= ( c3 & 0x3F );
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if( c0 >= 0x10000 && c0 <= 0x10FFFF ) {
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return { c0, 4 };
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}
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}
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}
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}
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return { 0, 0 };
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}
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};
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} // namespace TAO_PEGTL_NAMESPACE::internal
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#endif
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