/// <summary>
/// Try to make a callback in a transactional way.
/// </summary>
/// <param name="delegate">The callback to perform the match.</param>
/// <returns>true if the match could be made, false if not.</returns>
protected bool TryMake(TryMakeDelegate @delegate)
{
var checkpoint = Enumerator.Checkpoint();
if (@delegate() == false)
{
checkpoint.Rollback();
return(false);
}
checkpoint.Dispose();
return(true);
}
/// <summary>
/// Try to make a callback in a transactional way.
/// </summary>
/// <param name="delegate">The callback to perform the match.</param>
/// <param name="found">The parameter that was returned from the matching function.</param>
/// <returns>true if the match could be made, false if not.</returns>
protected bool TryMake <TOut>(TryMakeDelegate <TOut> @delegate, out TOut found)
{
var checkpoint = Enumerator.Checkpoint();
if (@delegate(out found) == false)
{
checkpoint.Rollback();
return(false);
}
checkpoint.Dispose();
return(true);
}
/// <summary>
/// Try to take the tokens in sequence.
/// </summary>
/// <param name="tokens">The list of tokens to take in sequence.</param>
/// <returns>true if the given list of tokens could be made in sequence, false if not.</returns>
protected bool TryTakeTokens(params Token[] tokens)
{
var checkpoint = Enumerator.Checkpoint();
foreach (var token in tokens)
{
if (Enumerator.Take() != token)
{
checkpoint.Rollback();
return(false);
}
}
checkpoint.Dispose();
return(true);
}
/// <summary>
/// Try to extract IPv6 address. https://tools.ietf.org/html/rfc4291 section 2.2 used for specification.
/// </summary>
/// <param name="address">Extracted Ipv6 address</param>
/// <returns>true if a valid Ipv6 address can be extracted</returns>
public bool TryMakeIpv6AddressLiteral(out string address)
{
address = null;
if ((TryMake(TryMakeIpVersion, out int ipVersion) == false) || ipVersion != 6)
{
return(false);
}
var hasDoubleColumn = false;
var hexPartCount = 0;
var hasIpv4Part = false;
var wasColon = false;
var token = Enumerator.Peek();
var builder = new System.Text.StringBuilder();
while (token.Kind == TokenKind.Number || token.Kind == TokenKind.Text || token == Tokens.Colon)
{
using (var cp = Enumerator.Checkpoint())
{
Enumerator.Take();
// Alternate form with mixed IPv6 and IPv4 formats. See https://tools.ietf.org/html/rfc4291 section 2.2 item 3
if (token.Kind == TokenKind.Number && Enumerator.Peek() == Tokens.Period)
{
cp.Rollback();
if (TryMake(TryMakeIpv4AddressLiteral, out string ipv4))
{
hasIpv4Part = true;
builder.Append(ipv4);
break;
}
else
{
return(false);
}
}
else
{
cp.Rollback();
}
}
if (token == Tokens.Colon)
{
if (wasColon)
{
// Double column is allowed only once
if (hasDoubleColumn)
{
return(false);
}
hasDoubleColumn = true;
}
builder.Append(token.Text);
wasColon = true;
Enumerator.Take();
}
else
{
if (wasColon == false && builder.Length > 0)
{
return(false);
}
wasColon = false;
if (TryMake(TryMake16BitsHexNumber, out string hexNumber))
{
builder.Append(hexNumber);
hexPartCount++;
}
else
{
return(false);
}
}
token = Enumerator.Peek();
}
address = builder.ToString();
var maxAllowedParts = (hasIpv4Part ? 6 : 8) - Math.Sign(hasDoubleColumn ? 1 : 0);
if ((hasDoubleColumn && hexPartCount > maxAllowedParts) || (!hasDoubleColumn && hexPartCount != maxAllowedParts))
{
return(false);
}
return(true);
}