! @brief check whether a string is UTF-8 encoded The function checks each byte of a string whether it is UTF-8 encoded. The result of the check is stored in the @a state parameter. The function must be called initially with state 0 (accept). State 1 means the string must be rejected, because the current byte is not allowed. If the string is completely processed, but the st
| 18910 | @sa http://bjoern.hoehrmann.de/utf-8/decoder/dfa/ |
| 18911 | */ |
| 18912 | static std::uint8_t decode(std::uint8_t& state, std::uint32_t& codep, const std::uint8_t byte) noexcept |
| 18913 | { |
| 18914 | static const std::array<std::uint8_t, 400> utf8d = |
| 18915 | { |
| 18916 | { |
| 18917 | 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 00..1F |
| 18918 | 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 20..3F |
| 18919 | 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 40..5F |
| 18920 | 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, // 60..7F |
| 18921 | 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, // 80..9F |
| 18922 | 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, // A0..BF |
| 18923 | 8, 8, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, // C0..DF |
| 18924 | 0xA, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x3, 0x4, 0x3, 0x3, // E0..EF |
| 18925 | 0xB, 0x6, 0x6, 0x6, 0x5, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, 0x8, // F0..FF |
| 18926 | 0x0, 0x1, 0x2, 0x3, 0x5, 0x8, 0x7, 0x1, 0x1, 0x1, 0x4, 0x6, 0x1, 0x1, 0x1, 0x1, // s0..s0 |
| 18927 | 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1, 1, 1, 1, 1, 0, 1, 0, 1, 1, 1, 1, 1, 1, // s1..s2 |
| 18928 | 1, 2, 1, 1, 1, 1, 1, 2, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, // s3..s4 |
| 18929 | 1, 2, 1, 1, 1, 1, 1, 1, 1, 2, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 1, // s5..s6 |
| 18930 | 1, 3, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1 // s7..s8 |
| 18931 | } |
| 18932 | }; |
| 18933 | |
| 18934 | JSON_ASSERT(byte < utf8d.size()); |
| 18935 | const std::uint8_t type = (byte >= 0 && byte < 400) ? utf8d[byte] : 0; |
| 18936 | |
| 18937 | codep = (state != UTF8_ACCEPT) |
| 18938 | ? (byte & 0x3fu) | (codep << 6u) |
| 18939 | : (0xFFu >> type) & (byte); |
| 18940 | |
| 18941 | const std::size_t index = 256u + static_cast<size_t>(state) * 16u + static_cast<size_t>(type); |
| 18942 | JSON_ASSERT(index < utf8d.size()); |
| 18943 | state = utf8d[index]; |
| 18944 | return state; |
| 18945 | } |
| 18946 | |
| 18947 | /* |
| 18948 | * Overload to make the compiler happy while it is instantiating |