Issue287: create random password from a set of allowed characters

[anna-liao]

fixes #287 r? @budziq

I categorized this example under text processing. Do you think that is the appropriate category?

[ludwigpacifici]

Can you give more details, such as gen_ascii_chars is the method which a hardcoded range of character.

Plus, I would show the choose method which is a user defined set of allowed characters. Maybe wait for the green flag of @budziq for this one.

[budziq]

Agreed on both arguments:

• lets add links to key identifiers in the description.
• I'd suggest to add two snippets here the second one being an iterator based in choose like the one used to implement gen_ascii_chars but taking arbitrary bytestring in the constructor, then used in identical fashion as the first trivial snippet. That would be very cool!

[budziq]

few suggestions

[budziq]

few suggestions

[budziq]

I'd remove the "text-processing" category. We are not really doing any processing of input text.

[budziq]

lets run rustfmt on the snippet

[budziq]

Agreed on both arguments:

• lets add links to key identifiers in the description.
• I'd suggest to add two snippets here the second one being an iterator based in choose like the one used to implement gen_ascii_chars but taking arbitrary bytestring in the constructor, then used in identical fashion as the first trivial snippet. That would be very cool!

[anna-liao]

r? @budziq @ludwigpacifici I added an example with choose. Was hoping to add punctuation into the bytestring, but the function call (commented out with //) doesn't work.

[budziq]

Thanks @anna-liao ! few suggestions below:

• I would split this example into two separate code snippets.

[budziq]

Thanks @anna-liao ! few suggestions below:

• I would split this example into two separate code snippets.

[budziq]

lets use wildcard version numbers

[budziq]

lets use wildcard version numbers

[budziq]

I'd suggest implementing an iterator type like the AsciiGenerator instead that would take an rng in a constructor and for added merrit a "charset" (a hardcoded bytestr for our purposes without anych dynamic generation with ranges and chain) as an argument.

Then it would be used almost identically as the gen_ascii_chars

[budziq]

If the iterator approach would be used, pretty much all of this code would be not needed.

[budziq]

there should be a category here

[budziq]

there should be a category here

[budziq]

It does not work because ranges give you u8 while iterating over slice gives you &u8 so the solution (if we wanted to go with this approach and we do not ;)) would be to clone the iterator contents.
.chain([b'!', b'?', b'%'].iter().cloned()) or even better .chain(b"!?%".iter().cloned()).

On the other hand I would suggest to just go with bytestring literal

const CHARSET: &[u8] =  b"ABCDEFGHIJKLMNOPQRSTUVWXYZ\
              abcdefghijklmnopqrstuvwxyz\
              0123456789)(*&^%$#@!~";

[anna-liao]

@budziq Thanks for the review. I revised the PR based on your suggestions. With the choose example, if I manually compose the vec it seems to work, but I am having issues writing an interator like for AsciiGenerator. Can you provide some guidance on how to write CustomGenerator to work properly?

[budziq]

@anna-liao few suggestions below :)

[budziq]

@anna-liao few suggestions below :)

[budziq]

lets change the variable name to a more descriptive one.

[budziq]

instead of for loop you can use a relatively simpler functional appproach without a need for manual string append. Also obtaining a thread_rng might be relatively costly so lets reuse one instance througth the generation process.

    let mut rng = thread_rng();
    let password: String = (0..30)
        .map(|_| *rng.choose(CHARSET).unwrap() as char)
        .collect();

This version might be more readable and concise than separate type approach with CustomGenerator so I'll leave it up to you to chose one.

[budziq]

I guess that you are trying to emulate the gen_ascii_chars method here but it is not possible to extend the Rng in such way. All we can do is prepare a standard constructor that will take an rng and a charset.

Some along the lines of

impl<'a, R> CustomGenerator<'a, R> {
    fn new(rng: R, charset: &'a [u8]) -> Result<Self> {
        if charset.len() > 0 {
            Some(CustomGenerator {
                rng: rng,
                charset: charset,
            })
        } else {
                 Err(ErrorKind::InvalidCharset.into())
        }
    }
}

[budziq]

I'd probably go with owing the rng to make the lifetimes simpler. But I'll leave it up to you :)
We might go with having a refference to some outsude charset

[anna-liao]

@budziq Thanks for the help! I have learned more about idiomatic Rust syntax. I decided to stick with the non-generator case for user-specified charset. I couldn't get the generator case working. I think the generator case would be good as an additional example?

[budziq]

Minor suggestions in a review

I couldn't get the generator case working.

No problem it is a bit verbose anyway

[budziq]

Minor suggestions in a review

I couldn't get the generator case working.

No problem it is a bit verbose anyway

[budziq]

we generally avoid unwrap in the examples, we should either document why the unwrap will be always ok as long as the CHARSET is nonempty or provide a generalized solution like:

    let password: Option<String> = (0..30)
        .map(|_| Some(*rng.choose(CHARSET)? as char))
        .collect();

    println!("{:?}", password);

[anna-liao]

@budziq Thanks for showing me how to implement the generator case! I have updated the PR as suggested to remove the unwrap() and print an Option instead.