Function readFloatText

base/base/JSON.cpp:100–164

Read floating point number in simple format, imprecisely, from a non-0-terminated string.

/// Read floating point number in simple format, imprecisely, from a non-0-terminated string.
static double readFloatText(const char * buf, const char * end)
{
    bool negative = false;
    double x = 0;
    bool after_point = false;
    double power_of_ten = 1;

    if (buf == end)
        throw JSONException("JSON: cannot parse floating point number: unexpected end of data.");

    bool run = true;
    while (buf != end && run)
    {
        switch (*buf)
        {
            case '+':
                break;
            case '-':
                negative = true;
                break;
            case '.':
                after_point = true;
                break;
            case '0':
            case '1':
            case '2':
            case '3':
            case '4':
            case '5':
            case '6':
            case '7':
            case '8':
            case '9':
                if (after_point)
                {
                    power_of_ten /= 10;
                    x += (*buf - '0') * power_of_ten;
                }
                else
                {
                    x *= 10;
                    x += *buf - '0';
                }
                break;
            case 'e':
            case 'E':
            {
                ++buf;
                auto exponent = readIntText(buf, end);
                x *= preciseExp10(static_cast<double>(exponent));

                run = false;
                break;
            }
            default:
                run = false;
                break;
        }