ClickHouse/src/Common/isValidUTF8.cpp

#include <Common/isValidUTF8.h>
#include <cstring>

/// inspired by https://github.com/cyb70289/utf8/

/*
MIT License

Copyright (c) 2019 Yibo Cai

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.
*/

/*
* http://www.unicode.org/versions/Unicode6.0.0/ch03.pdf - page 94
*
* Table 3-7. Well-Formed UTF-8 Byte Sequences
*
* +--------------------+------------+-------------+------------+-------------+
* | Code Points        | First Byte | Second Byte | Third Byte | Fourth Byte |
* +--------------------+------------+-------------+------------+-------------+
* | U+0000..U+007F     | 00..7F     |             |            |             |
* +--------------------+------------+-------------+------------+-------------+
* | U+0080..U+07FF     | C2..DF     | 80..BF      |            |             |
* +--------------------+------------+-------------+------------+-------------+
* | U+0800..U+0FFF     | E0         | A0..BF      | 80..BF     |             |
* +--------------------+------------+-------------+------------+-------------+
* | U+1000..U+CFFF     | E1..EC     | 80..BF      | 80..BF     |             |
* +--------------------+------------+-------------+------------+-------------+
* | U+D000..U+D7FF     | ED         | 80..9F      | 80..BF     |             |
* +--------------------+------------+-------------+------------+-------------+
* | U+E000..U+FFFF     | EE..EF     | 80..BF      | 80..BF     |             |
* +--------------------+------------+-------------+------------+-------------+
* | U+10000..U+3FFFF   | F0         | 90..BF      | 80..BF     | 80..BF      |
* +--------------------+------------+-------------+------------+-------------+
* | U+40000..U+FFFFF   | F1..F3     | 80..BF      | 80..BF     | 80..BF      |
* +--------------------+------------+-------------+------------+-------------+
* | U+100000..U+10FFFF | F4         | 80..8F      | 80..BF     | 80..BF      |
* +--------------------+------------+-------------+------------+-------------+
*/
namespace DB
{

namespace UTF8
{

UInt8 isValidUTF8(const UInt8 * data, UInt64 len)
{
    while (len)
    {
        int bytes;
        const UInt8 byte1 = data[0];
        /* 00..7F */
        if (byte1 <= 0x7F)
        {
            bytes = 1;
        }
        /* C2..DF, 80..BF */
        else if (len >= 2 && byte1 >= 0xC2 && byte1 <= 0xDF && static_cast<Int8>(data[1]) <= static_cast<Int8>(0xBF))
        {
            bytes = 2;
        }
        else if (len >= 3)
        {
            const UInt8 byte2 = data[1];
            bool byte2_ok = static_cast<Int8>(byte2) <= static_cast<Int8>(0xBF);
            bool byte3_ok = static_cast<Int8>(data[2]) <= static_cast<Int8>(0xBF);

            if (byte2_ok && byte3_ok &&
                /* E0, A0..BF, 80..BF */
                ((byte1 == 0xE0 && byte2 >= 0xA0) ||
                 /* E1..EC, 80..BF, 80..BF */
                 (byte1 >= 0xE1 && byte1 <= 0xEC) ||
                 /* ED, 80..9F, 80..BF */
                 (byte1 == 0xED && byte2 <= 0x9F) ||
                 /* EE..EF, 80..BF, 80..BF */
                 (byte1 >= 0xEE && byte1 <= 0xEF)))
            {
                bytes = 3;
            }
            else if (len >= 4)
            {
                bool byte4_ok = static_cast<Int8>(data[3]) <= static_cast<Int8>(0xBF);
                if (byte2_ok && byte3_ok && byte4_ok &&
                    /* F0, 90..BF, 80..BF, 80..BF */
                    ((byte1 == 0xF0 && byte2 >= 0x90) ||
                     /* F1..F3, 80..BF, 80..BF, 80..BF */
                     (byte1 >= 0xF1 && byte1 <= 0xF3) ||
                     /* F4, 80..8F, 80..BF, 80..BF */
                     (byte1 == 0xF4 && byte2 <= 0x8F)))
                {
                    bytes = 4;
                }
                else
                {
                    return false;
                }
            }
            else
            {
                return false;
            }
        }
        else
        {
            return false;
        }
        len -= bytes;
        data += bytes;
    }
    return true;
}

}
}