Function format_buffer

Source/external/json.hpp:17763–17831

JSON_HEDLEY_NON_NULL(1)
JSON_HEDLEY_RETURNS_NON_NULL
inline char* format_buffer(char* buf, int len, int decimal_exponent,
						   int min_exp, int max_exp)
{
	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
	{