//
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// Copyright (c) 2020 Krystian Stasiowski (sdkrystian@gmail.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_UTF8_HPP
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#define BOOST_JSON_DETAIL_UTF8_HPP
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#include <cstddef>
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#include <cstring>
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#include <cstdint>
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BOOST_JSON_NS_BEGIN
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namespace detail {
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template<int N>
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std::uint32_t
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load_little_endian(void const* p)
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{
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// VFALCO do we need to initialize this to 0?
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std::uint32_t v;
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std::memcpy(&v, p, N);
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#ifdef BOOST_JSON_BIG_ENDIAN
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v = ((v & 0xFF000000) >> 24) |
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((v & 0x00FF0000) >> 8) |
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((v & 0x0000FF00) << 8) |
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((v & 0x000000FF) << 24);
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#endif
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return v;
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}
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inline
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uint16_t
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classify_utf8(char c)
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{
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// 0x000 = invalid
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// 0x102 = 2 bytes, second byte [80, BF]
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// 0x203 = 3 bytes, second byte [A0, BF]
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// 0x303 = 3 bytes, second byte [80, BF]
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// 0x403 = 3 bytes, second byte [80, 9F]
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// 0x504 = 4 bytes, second byte [90, BF]
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// 0x604 = 4 bytes, second byte [80, BF]
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// 0x704 = 4 bytes, second byte [80, 8F]
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static constexpr uint16_t first[128]
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{
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0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000,
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0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000,
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0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000,
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0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000,
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0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000,
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0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000,
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0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000,
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0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000,
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0x000, 0x000, 0x102, 0x102, 0x102, 0x102, 0x102, 0x102,
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0x102, 0x102, 0x102, 0x102, 0x102, 0x102, 0x102, 0x102,
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0x102, 0x102, 0x102, 0x102, 0x102, 0x102, 0x102, 0x102,
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0x102, 0x102, 0x102, 0x102, 0x102, 0x102, 0x102, 0x102,
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0x203, 0x303, 0x303, 0x303, 0x303, 0x303, 0x303, 0x303,
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0x303, 0x303, 0x303, 0x303, 0x303, 0x403, 0x303, 0x303,
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0x504, 0x604, 0x604, 0x604, 0x704, 0x000, 0x000, 0x000,
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0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000, 0x000,
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};
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return first[static_cast<unsigned char>(c)];
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}
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inline
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bool
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is_valid_utf8(const char* p, uint16_t first)
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{
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uint32_t v;
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switch(first >> 8)
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{
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default:
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return false;
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// 2 bytes, second byte [80, BF]
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case 1:
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v = load_little_endian<2>(p);
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return (v & 0xC000) == 0x8000;
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// 3 bytes, second byte [A0, BF]
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case 2:
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v = load_little_endian<3>(p);
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std::memcpy(&v, p, 3);
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return (v & 0xC0E000) == 0x80A000;
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// 3 bytes, second byte [80, BF]
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case 3:
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v = load_little_endian<3>(p);
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return (v & 0xC0C000) == 0x808000;
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// 3 bytes, second byte [80, 9F]
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case 4:
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v = load_little_endian<3>(p);
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return (v & 0xC0E000) == 0x808000;
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// 4 bytes, second byte [90, BF]
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case 5:
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v = load_little_endian<4>(p);
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return (v & 0xC0C0FF00) + 0x7F7F7000 <= 0x2F00;
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// 4 bytes, second byte [80, BF]
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case 6:
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v = load_little_endian<4>(p);
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return (v & 0xC0C0C000) == 0x80808000;
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// 4 bytes, second byte [80, 8F]
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case 7:
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v = load_little_endian<4>(p);
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return (v & 0xC0C0F000) == 0x80808000;
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}
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}
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class utf8_sequence
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{
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char seq_[4];
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uint16_t first_;
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uint8_t size_;
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public:
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void
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save(
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const char* p,
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std::size_t remain) noexcept
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{
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first_ = classify_utf8(*p & 0x7F);
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if(remain >= length())
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size_ = length();
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else
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size_ = static_cast<uint8_t>(remain);
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std::memcpy(seq_, p, size_);
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}
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uint8_t
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length() const noexcept
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{
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return first_ & 0xFF;
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}
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bool
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complete() const noexcept
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{
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return size_ >= length();
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}
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// returns true if complete
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bool
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append(
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const char* p,
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std::size_t remain) noexcept
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{
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if(BOOST_JSON_UNLIKELY(needed() == 0))
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return true;
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if(BOOST_JSON_LIKELY(remain >= needed()))
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{
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std::memcpy(
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seq_ + size_, p, needed());
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size_ = length();
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return true;
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}
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if(BOOST_JSON_LIKELY(remain > 0))
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{
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std::memcpy(seq_ + size_, p, remain);
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size_ += static_cast<uint8_t>(remain);
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}
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return false;
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}
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const char*
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data() const noexcept
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{
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return seq_;
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}
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uint8_t
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needed() const noexcept
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{
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return length() - size_;
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}
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bool
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valid() const noexcept
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{
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BOOST_ASSERT(size_ >= length());
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return is_valid_utf8(seq_, first_);
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}
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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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