path: root/libdevcore/UTF8.cpp

/*
    This file is part of solidity.

    solidity is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation, either version 3 of the License, or
    (at your option) any later version.

    solidity is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with solidity.  If not, see <http://www.gnu.org/licenses/>.
*/
/** @file UTF8.cpp
 * @author Alex Beregszaszi
 * @date 2016
 *
 * UTF-8 related helpers
 */

#include "UTF8.h"


namespace dev
{

namespace
{

/// Validate byte sequence against Unicode chapter 3 Table 3-7.
bool isWellFormed(unsigned char byte1, unsigned char byte2)
{
    switch (byte1)
    {
    case 0xc0 ... 0xc1:
        return false;
    case 0xc2 ... 0xdf:
        break;
    case 0xe0:
        if (byte2 < 0xa0)
            return false;
        break;
    case 0xe1 ... 0xec:
        break;
    case 0xed:
        if (byte2 > 0x9f)
            return false;
        break;
    case 0xee ... 0xef:
        break;
    case 0xf0:
        if (byte2 < 0x90)
            return false;
        break;
    case 0xf1 ... 0xf3:
        break;
    case 0xf4:
        if (byte2 > 0x8f)
            return false;
        break;
    case 0xf5 ... 0xf7:
    default:
        /// Technically anything below 0xc0 or above 0xf7 is
        /// not possible to encode using Table 3-6 anyway.
        return false;
    }
    return true;
}

}

bool validateUTF8(std::string const& _input, size_t& _invalidPosition)
{
    const size_t length = _input.length();
    bool valid = true;
    size_t i = 0;

    for (; i < length; i++)
    {
        // Check for Unicode Chapter 3 Table 3-6 conformity.
        if ((unsigned char)_input[i] < 0x80)
            continue;

        size_t count = 0;
        switch ((unsigned char)_input[i])
        {
            case 0xc0 ... 0xdf:
                count = 1;
                break;
            case 0xe0 ... 0xef:
                count = 2;
                break;
            case 0xf0 ... 0xf7:
                count = 3;
                break;
            default:
                break;
        }

        if (count == 0)
        {
            valid = false;
            break;
        }

        if ((i + count) >= length)
        {
            valid = false;
            break;
        }

        for (size_t j = 0; j < count; j++)
        {
            i++;
            if ((_input[i] & 0xc0) != 0x80)
            {
                valid = false;
                break;
            }

            // Check for Unicode Chapter 3 Table 3-7 conformity.
            if ((j == 0) && !isWellFormed(_input[i - 1], _input[i]))
            {
                valid = false;
                break;
            }
        }
    }

    if (valid)
        return true;

    _invalidPosition = i;
    return false;
}

}