internal static bool TryParse(ref Tokenizer tokenizer, out IpAddressV6 result)
{
// Shortest IPv6 is 2 chars (::)
// Longest regular IPv6 is 39 chars (0000:0000:0000:0000:0000:0000:0000:0000)
// Longest IPv4 mapped IPv6 is 45 chars (0000:0000:0000:0000:0000:ffff:255.255.255.255)
if (tokenizer.Length < 2 || tokenizer.Length > 45)
{
result = default;
return(false);
}
ulong high = 0;
ulong low = 0;
byte segmentsRead = 0;
bool doReverse = false;
// First pass, try reading a mask from the end of the input
ParsedToken tkn = tokenizer.PeekReverse(false);
if (tkn.Type == TokenType.Number)
{
// Could be a number, therefore an IPv4 mapped IPv6
ParsedToken slashTkn = tokenizer.PeekReverse(false);
if (slashTkn.Type == TokenType.Dot)
{
// This could be an IPv4 mapped in IPv6
// Carry on, see where it gets us
tokenizer.ResetPeekOffsets();
}
else if (slashTkn.Type != TokenType.Number && slashTkn.Type != TokenType.Colon && slashTkn.Type != TokenType.DoubleColon && slashTkn.Type != TokenType.None)
{
// Any IPv6 should end on a number or double-colon
// Single-token IPv6's are allowed, so we check for None as well
result = default;
return(false);
}
}
// Test if this could be an IPv4 mapped IPv6
// This could be the case if the last two tokens are [Dot, Number]
// Like '::ffff:192.168.1.0'
tkn = tokenizer.PeekReverse(false);
if (tkn.Type == TokenType.Number)
{
// If the next-to-last is a Dot, pass it on
ParsedToken tmpTkn = tokenizer.PeekReverse(false);
tokenizer.ResetPeekOffsets();
if (tmpTkn.Type == TokenType.Dot)
{
return(TryReadIPv4MappedIPv6(tokenizer, out result));
}
}
tokenizer.ResetPeekOffsets();
// Read up till a double-colon, eof or slash
for (byte i = 0; i < 8; i++)
{
tkn = tokenizer.ParseAndAdvance(true);
if (tkn.Type == TokenType.None)
{
break;
}
if (i > 0)
{
// The read token MUST be a colon or a double-colon
if (tkn.Type == TokenType.Colon)
{
// Advance once more
tkn = tokenizer.ParseAndAdvance(true);
}
else if (tkn.Type != TokenType.DoubleColon)
{
result = default;
return(false);
}
}
// Read a number or double-colon
if (tkn.Type == TokenType.Number)
{
BitUtilities.SetTuplet(ref low, ref high, i, tkn.Value);
segmentsRead++;
}
else if (tkn.Type == TokenType.DoubleColon)
{
doReverse = true;
break;
}
else if (tkn.Type != TokenType.DoubleColon)
{
result = default;
return(false);
}
}
// Read reverse
if (doReverse)
{
byte toRead = (byte)(8 - segmentsRead);
for (byte i = 0; i < toRead; i++)
{
tkn = tokenizer.ParseAndAdvanceReverse(true);
if (tkn.Type == TokenType.None)
{
break;
}
if (i > 0)
{
// The read token MUST be a colon
if (tkn.Type != TokenType.Colon)
{
result = default;
return(false);
}
// Advance once more
tkn = tokenizer.ParseAndAdvanceReverse(true);
}
// Read a number
if (tkn.Type == TokenType.Number)
{
BitUtilities.SetTuplet(ref low, ref high, (byte)(7 - i), tkn.Value);
segmentsRead++;
}
else
{
result = default;
return(false);
}
}
}
result = new IpAddressV6(high, low);
return(true);
}
private static bool TryReadIPv4MappedIPv6(Tokenizer tokenizer, out IpAddressV6 result)
{
ulong high = 0;
ulong low = 0;
byte segmentsRead = 0;
ParsedToken token;
// Read reverse, we're only interested in the IPv4 on the end
byte toRead = 4;
for (byte i = 0; i < toRead; i++)
{
token = tokenizer.ParseAndAdvanceReverse(false);
if (token.Type == TokenType.None)
{
break;
}
if (i > 0)
{
// The read token MUST be a dot
if (token.Type != TokenType.Dot)
{
result = default;
return(false);
}
// Advance once more
token = tokenizer.ParseAndAdvanceReverse(false);
}
// Read a number
if (token.Type == TokenType.Number)
{
BitUtilities.SetByte(ref low, ref high, (byte)(15 - i), token.Value);
segmentsRead++;
}
else
{
result = default;
return(false);
}
}
// Assert that the next tokens are [Double-/Colon, ffff, Colon]
token = tokenizer.ParseAndAdvanceReverse(false);
if (token.Type != TokenType.Colon)
{
result = default;
return(false);
}
token = tokenizer.ParseAndAdvanceReverse(true);
if (token.Type != TokenType.Number || token.Value != 0xffff)
{
result = default;
return(false);
}
token = tokenizer.ParseAndAdvanceReverse(false);
if (token.Type is not TokenType.Colon && token.Type is not TokenType.DoubleColon)
{
result = default;
return(false);
}
// Place 0xFFFF in the correct position
BitUtilities.SetTuplet(ref low, ref high, 5, 0xFFFF);
result = new IpAddressV6(high, low);
return(true);
}
