Iterate over all cards in a header

[chrsoo]

Hi,

From what I can tell the fitsrs library only supports retrieving Cards of a Header by Keyword.

Is this correct or is there a way of iterate over all Cards in Header that does not assume prior knowledge of the possible Keywords?

[bmatthieu3]

Hi @chrsoo,

Thank you, I merged the PR with 2,3 unrelated things (git-lfs removal among others).

I added a test retrieving calling cards iter. I realize Keyword may not be very friendly from the user perspective. As a minor future update, would it be better to have a proper Keyword type being just a [u8; 8] that has a method to get its owned String trimmed value (the method you made on Card) ? What do you think ?

[chrsoo]

Great, thanks!

I just realised that the Card method really should have been a &str like so:

impl Card {
    ...
    /// Return the ASCII trimmed keyword.
    pub fn keyword(&self) -> Result<&str, std::str::Utf8Error> {
        std::str::from_utf8(self.kw.trim_ascii())
    }
}

No point in copying the buffer if an owned value is not needed. If an owned value is needed there is &str.to_owned() or &str.to_string().

Regarding Keyword as a struct wrapping [u8;8], it could make sense, but I am wondering why we are not using strings? Why not parse it up front when reading the keyword from file?

The convenience method I added is only half-way as a keyword should be infallible. Per the FITS standard the whole header must conform to valid ASCII. Should the UTF8 conversion fail all the same, I think the header record should be ignored and a parser error logged or written to stderr.