Txt long values

[Nuhvi]

closes #22

Two changes:

1. create TXT from a long string, and convert TXT into a String.
2. txt.attributes() operates on the entire value, and respects ; seperators.

[Nuhvi]

Check for valid utf-8 (and add a test for it), to be able to unwrap at line 44 safely.

[balliegojr]

I think this check can't be used here, because a character string is not necessarily valid utf-8. If you check this section of the RFC-1035, it says that character string must be treated as binary data.

Since this library can receive records from other libraries, the safest place to check for a valid utf8 string is in the ''Into String" function, because it wouldn't impose valid utf8 when using the library to interface with something else.

[balliegojr]

Thank you very much for the PR.

I have added some suggestions and comments regarding compatibility.

BTW, sorry for taking this long to reply, I've missed the email and only saw it today

[balliegojr]

I think this check can't be used here, because a character string is not necessarily valid utf-8. If you check this section of the RFC-1035, it says that character string must be treated as binary data.

Since this library can receive records from other libraries, the safest place to check for a valid utf8 string is in the ''Into String" function, because it wouldn't impose valid utf8 when using the library to interface with something else.

[balliegojr]

I think it is better to create a new function, maybe long_attributes, rather than changing the existing functionality, because there may be people relying on the current behavior

[balliegojr]

This can be simplified if you implement for &str, and it would also avoid cloning the data

Suggested change

	impl<'a> TryFrom<String> for TXT<'a> {
	type Error = crate::SimpleDnsError;
	fn try_from(value: String) -> Result<Self, Self::Error> {
	let mut txt = TXT::new();
	let mut start_index = 0;
	let full_length = value.len();
	while start_index < full_length {
	let end_index = (start_index + MAX_CHARACTER_STRING_LENGTH).min(full_length);
	let slice = &value[start_index..end_index];
	txt.add_char_string(slice.to_string().try_into()?);
	start_index = end_index;
	}
	Ok(txt)
	}
	}
	impl<'a> TryFrom<&'a str> for TXT<'a> {
	type Error = crate::SimpleDnsError;
	fn try_from(value: &'a str) -> Result<Self, Self::Error> {
	let mut txt = TXT::new();
	for v in value.as_bytes().chunks(MAX_CHARACTER_STRING_LENGTH) {
	txt.add_char_string(CharacterString::new(v)?);
	}
	Ok(txt)
	}
	}

[balliegojr]

Here would be the proper place to check for a valid utf8 string, something like this

Suggested change

	impl<'a> From<TXT<'a>> for String {
	fn from(val: TXT<'a>) -> Self {
	val.strings
	.into_iter()
	.map(|s| s.into())
	.collect::<Vec<String>>()
	.join("")
	}
	}
	impl<'a> TryFrom<TXT<'a>> for String {
	type Error = std::string::FromUtf8Error;
	fn try_from(val: TXT<'a>) -> Result<Self, Self::Error> {
	let bytes = val
	.strings
	.into_iter()
	.fold(Vec::with_capacity(val.len()), |mut acc, val| {
	acc.extend(val.data.as_ref());
	acc
	});
	String::from_utf8(bytes)
	}
	}

[Nuhvi]

@balliegojr Thanks for the feedback, learned a lot, and surprisingly managed to apply the suggested changes without much trouble or adding even more cloning :)

[balliegojr]

Can you change this to a TryFrom implementaiton? Since it can be called in a CharacterString that is not valid utf8

[Nuhvi]

done