format_buffer()

JSON_HEDLEY_RETURNS_NON_NULL char * nlohmann::detail::dtoa_impl::format_buffer ( char *  buf, int  len, int  decimal_exponent, int  min_exp, int  max_exp  )

inline

prettify v = buf * 10^decimal_exponent

If v is in the range [10^min_exp, 10^max_exp) it will be printed in fixed-point notation. Otherwise it will be printed in exponential notation.

Precondition

min_exp < 0

max_exp > 0

Definition at line 16467 of file json.hpp.

{
    JSON_ASSERT(min_exp < 0);
    JSON_ASSERT(max_exp > 0);
    const int k = len;
    const int n = len + decimal_exponent;
 
    // v = buf * 10^(n-k)
    // k is the length of the buffer (number of decimal digits)
    // n is the position of the decimal point relative to the start of the buffer.
 
    if (k <= n && n <= max_exp)
    {
        // digits[000]
        // len <= max_exp + 2
        std::memset(buf + k, '0', static_cast<size_t>(n) - static_cast<size_t>(k));
        // Make it look like a floating-point number (#362, #378)
        buf[n + 0] = '.';
        buf[n + 1] = '0';
        return buf + (static_cast<size_t>(n) + 2);
    }
 
    if (0 < n && n <= max_exp)
    {
        // dig.its
        // len <= max_digits10 + 1
        JSON_ASSERT(k > n);
        std::memmove(buf + (static_cast<size_t>(n) + 1), buf + n, static_cast<size_t>(k) - static_cast<size_t>(n));
        buf[n] = '.';
        return buf + (static_cast<size_t>(k) + 1U);
    }
 
    if (min_exp < n && n <= 0)
    {
        // 0.[000]digits
        // len <= 2 + (-min_exp - 1) + max_digits10
        std::memmove(buf + (2 + static_cast<size_t>(-n)), buf, static_cast<size_t>(k));
        buf[0] = '0';
        buf[1] = '.';
        std::memset(buf + 2, '0', static_cast<size_t>(-n));
        return buf + (2U + static_cast<size_t>(-n) + static_cast<size_t>(k));
    }
 
    if (k == 1)
    {
        // dE+123
        // len <= 1 + 5
        buf += 1;
    }
 
    else
    {
        // d.igitsE+123
        // len <= max_digits10 + 1 + 5
        std::memmove(buf + 2, buf + 1, static_cast<size_t>(k) - 1);
        buf[1] = '.';
        buf += 1 + static_cast<size_t>(k);
    }
 
    *buf++ = 'e';
    return append_exponent(buf, n - 1);
}