double Value::readFloatText(const char * buf, size_t length) const
{
bool negative = false;
double x = 0;
bool after_point = false;
double power_of_ten = 1;
const char * end = buf + length;
while (buf != end)
{
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;
Int32 exponent = readIntText(buf, end - buf);
x *= preciseExp10(exponent);
if (negative)
x = -x;
return x;
}
case 'i':
case 'I':
x = std::numeric_limits<double>::infinity();
if (negative)
x = -x;
return x;
case 'n':
case 'N':
x = std::numeric_limits<double>::quiet_NaN();
return x;
default:
throwException("Cannot parse floating point number");
}
++buf;
}
if (negative)
x = -x;
return x;
}
/// Прочитать число с плавающей запятой в простом формате, с грубым округлением, из не-0-terminated строки.
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;
Int32 exponent = readIntText(buf, end);
x *= preciseExp10(exponent);
run = false;
break;
}
default:
run = false;
break;
}
++buf;
}
if (negative)
x = -x;
return x;
}
