/// <summary>
/// Converts an ASCII-encoded string to Unicode.
/// </summary>
/// <param name="input"> ASCII input string. </param>
/// <param name="allowUnassigned"> Allow unassigned Unicode characters. </param>
/// <param name="useSTD3ASCIIRules"> Check that the output conforms to STD3. </param>
/// <returns> Unicode string. </returns>
public static string ToUnicode(string input, bool allowUnassigned, bool useSTD3ASCIIRules)
{
string original = input;
bool nonASCII = false;
// Step 1: If all code points are inside 0..0x7f, skip to step 3.
for (int i = 0; i < input.Length; i++)
{
int c = input[i];
if (c > 0x7f)
{
nonASCII = true;
break;
}
}
// Step 2: Perform the Nameprep operation.
if (nonASCII)
{
try
{
input = Stringprep.NamePrep(input, allowUnassigned);
}
catch (StringprepException)
{
// ToUnicode never fails!
return(original);
}
}
// Step 3: Verify the sequence starts with the ACE prefix.
if (!input.StartsWith(ACE_PREFIX))
{
// ToUnicode never fails!
return(original);
}
string stored = input;
// Step 4: Remove the ACE prefix.
input = input.Substring(ACE_PREFIX.Length);
// Step 5: Decode using punycode
string output;
try
{
output = Punycode.Decode(input);
}
catch (PunycodeException)
{
// ToUnicode never fails!
return(original);
}
// Step 6: Apply toASCII
string ascii;
try
{
ascii = ToASCII(output, allowUnassigned, useSTD3ASCIIRules);
}
catch (IDNAException)
{
// ToUnicode never fails!
return(original);
}
// Step 7: Compare case-insensitively.
if (!ascii.ToUpper().Equals(stored.ToUpper()))
{
// ToUnicode never fails!
return(original);
}
// Step 8: Return the result.
return(output);
}
