public static ulong ToUInt64(string value, int fromBase)
{
// 使用内置方法，会快一些。
if (fromBase == 2 || fromBase == 8 || fromBase == 10 || fromBase == 16)
{
return(Convert.ToUInt64(value, fromBase));
}
// 使用自己的算法。
if (value == null)
{
return(0UL);
}
CheckBaseConvert(value, fromBase);
ulong result = 0;
ulong ulBase = (ulong)fromBase;
for (int i = 0; i < value.Length; i++)
{
int t = GetBaseValue(value[i], fromBase);
if (t < 0)
{
if (i == 0)
{
throw ExceptionHelper.NoParsibleDigits();
}
else
{
throw ExceptionHelper.ExtraJunkAtEnd();
}
}
ulong next = unchecked (result * ulBase + (ulong)t);
// 判断是否超出 UInt64 的范围。
if (next < result)
{
throw ExceptionHelper.OverflowUInt64();
}
result = next;
}
return(result);
}
