internal static bool TryGetUnicodeEquivalent(string hostname, ref ValueStringBuilder dest)
{
Debug.Assert(ReferenceEquals(hostname, UriHelper.StripBidiControlCharacters(hostname, hostname)));
int curPos = 0;
// We run a loop where for every label
// a) if label is ascii and no ace then we lowercase it
// b) if label is ascii and ace and not valid idn then just lowercase it
// c) if label is ascii and ace and is valid idn then get its unicode eqvl
// d) if label is unicode then clean it by running it through idnmapping
do
{
if (curPos != 0)
{
dest.Append('.');
}
bool asciiLabel = true;
//find the dot or hit the end
int newPos;
for (newPos = curPos; (uint)newPos < (uint)hostname.Length; newPos++)
{
char c = hostname[newPos];
if (c == '.')
{
break;
}
if (c > '\x7F')
{
asciiLabel = false;
if ((c == '\u3002') || // IDEOGRAPHIC FULL STOP
(c == '\uFF0E') || // FULLWIDTH FULL STOP
(c == '\uFF61')) // HALFWIDTH IDEOGRAPHIC FULL STOP
{
break;
}
}
}
if (!asciiLabel)
{
try
{
string asciiForm = s_idnMapping.GetAscii(hostname, curPos, newPos - curPos);
dest.Append(s_idnMapping.GetUnicode(asciiForm));
}
catch (ArgumentException)
{
return(false);
}
}
else
{
bool aceValid = false;
if ((uint)(curPos + 3) < (uint)hostname.Length &&
hostname[curPos] == 'x' &&
hostname[curPos + 1] == 'n' &&
hostname[curPos + 2] == '-' &&
hostname[curPos + 3] == '-')
{
// check ace validity
try
{
dest.Append(s_idnMapping.GetUnicode(hostname, curPos, newPos - curPos));
aceValid = true;
}
catch (ArgumentException)
{
// not valid ace so treat it as a normal ascii label
}
}
if (!aceValid)
{
// for invalid aces we just lowercase the label
ReadOnlySpan <char> slice = hostname.AsSpan(curPos, newPos - curPos);
int charsWritten = slice.ToLowerInvariant(dest.AppendSpan(slice.Length));
Debug.Assert(charsWritten == slice.Length);
}
}
curPos = newPos + 1;
} while (curPos < hostname.Length);
return(true);
}
