/// <summary>
/// Converts a Unicode string to ASCII using the procedure in RFC3490
/// section 4.1. Unassigned characters are not allowed and STD3 ASCII
/// rules are enforced.
/// </summary>
/// <param name="input">Unicode string.</param>
/// <param name="allowUnassigned">Unassigned characters, allowed or not?</param>
/// <param name="useSTD3ASCIIRules">STD3 ASCII rules, enforced or not?</param>
/// <returns> Encoded string.</returns>
public static string ToASCII(string input, bool allowUnassigned, bool useSTD3ASCIIRules)
{
// Step 1: Check if the string contains code points outside
// the ASCII range 0..0x7c.
var nonASCII = false;
for (var 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 e)
{
// TODO
throw new IDNAException(e);
}
}
// Step 3: - Verify the absence of non-LDH ASCII code points
// (char) 0..0x2c, 0x2e..0x2f, 0x3a..0x40, 0x5b..0x60,
// (char) 0x7b..0x7f
// - Verify the absence of leading and trailing
// hyphen-minus
if (useSTD3ASCIIRules)
{
for (var i = 0; i < input.Length; i++)
{
int c = input[i];
if ((c <= 0x2c) || (c >= 0x2e && c <= 0x2f) || (c >= 0x3a && c <= 0x40) || (c >= 0x5b && c <= 0x60) ||
(c >= 0x7b && c <= 0x7f))
{
throw new IDNAException(IDNAException.CONTAINS_NON_LDH);
}
}
if (input.StartsWith("-") || input.EndsWith("-"))
{
throw new IDNAException(IDNAException.CONTAINS_HYPHEN);
}
}
// Step 4: If all code points are inside 0..0x7f, skip to step 8
nonASCII = false;
for (var i = 0; i < input.Length; i++)
{
int c = input[i];
if (c > 0x7f)
{
nonASCII = true;
break;
}
}
var output = input;
if (nonASCII)
{
// Step 5: Verify that the sequence does not begin with the ACE prefix.
if (input.StartsWith(ACE_PREFIX))
{
throw new IDNAException(IDNAException.CONTAINS_ACE_PREFIX);
}
// Step 6: Punycode
try
{
output = Punycode.Encode(input);
}
catch (PunycodeException e)
{
// TODO
throw new IDNAException(e);
}
// Step 7: Prepend the ACE prefix.
output = ACE_PREFIX + output;
}
// Step 8: Check that the length is inside 1..63.
if (output.Length < 1 || output.Length > 63)
{
throw new IDNAException(IDNAException.TOO_LONG);
}
return(output);
}
/// <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)
{
var original = input;
var nonASCII = false;
// Step 1: If all code points are inside 0..0x7f, skip to step 3.
for (var 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);
}
var 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);
}