124 lines
2.5 KiB
Plaintext
124 lines
2.5 KiB
Plaintext
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//
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// Copyright (c) 2019 Vinnie Falco (vinnie.falco@gmail.com)
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// Copyright (c) 2020 Peter Dimov (pdimov at gmail dot com),
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//
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// Distributed under the Boost Software License, Version 1.0. (See accompanying
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// file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
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//
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// Official repository: https://github.com/boostorg/json
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//
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#ifndef BOOST_JSON_DETAIL_IMPL_FORMAT_IPP
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#define BOOST_JSON_DETAIL_IMPL_FORMAT_IPP
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#include <boost/json/detail/ryu/ryu.hpp>
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#include <cstring>
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BOOST_JSON_NS_BEGIN
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namespace detail {
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/* Reference work:
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https://www.ampl.com/netlib/fp/dtoa.c
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https://www.exploringbinary.com/fast-path-decimal-to-floating-point-conversion/
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https://kkimdev.github.io/posts/2018/06/15/IEEE-754-Floating-Point-Type-in-C++.html
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*/
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inline char const* digits_lut() noexcept
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{
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return
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"00010203040506070809"
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"10111213141516171819"
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"20212223242526272829"
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"30313233343536373839"
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"40414243444546474849"
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"50515253545556575859"
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"60616263646566676869"
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"70717273747576777879"
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"80818283848586878889"
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"90919293949596979899";
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}
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inline void format_four_digits( char * dest, unsigned v )
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{
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std::memcpy( dest + 2, digits_lut() + (v % 100) * 2, 2 );
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std::memcpy( dest , digits_lut() + (v / 100) * 2, 2 );
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}
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inline void format_two_digits( char * dest, unsigned v )
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{
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std::memcpy( dest, digits_lut() + v * 2, 2 );
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}
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inline void format_digit( char * dest, unsigned v )
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{
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*dest = static_cast<char>( v + '0' );
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}
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unsigned
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format_uint64(
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char* dest,
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std::uint64_t v) noexcept
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{
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if(v < 10)
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{
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*dest = static_cast<char>( '0' + v );
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return 1;
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}
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char buffer[ 24 ];
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char * p = buffer + 24;
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while( v >= 1000 )
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{
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p -= 4;
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format_four_digits( p, v % 10000 );
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v /= 10000;
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}
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if( v >= 10 )
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{
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p -= 2;
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format_two_digits( p, v % 100 );
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v /= 100;
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}
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if( v )
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{
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p -= 1;
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format_digit( p, static_cast<unsigned>(v) );
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}
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unsigned const n = static_cast<unsigned>( buffer + 24 - p );
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std::memcpy( dest, p, n );
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return n;
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}
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unsigned
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format_int64(
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char* dest, int64_t i) noexcept
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{
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std::uint64_t ui = static_cast<
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std::uint64_t>(i);
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if(i >= 0)
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return format_uint64(dest, ui);
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*dest++ = '-';
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ui = ~ui + 1;
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return 1 + format_uint64(dest, ui);
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}
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unsigned
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format_double(
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char* dest, double d) noexcept
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{
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return static_cast<int>(
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ryu::d2s_buffered_n(d, dest));
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}
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} // detail
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BOOST_JSON_NS_END
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#endif
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