use std::fmt; use std::borrow::Cow; use rocket::request::FromParam; use rand::{self, Rng}; /// Table to retrieve base62 values from. const BASE62: &'static [u8] = b"0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz"; /// A _probably_ unique paste ID. pub struct PasteID<'a>(Cow<'a, str>); impl<'a> PasteID<'a> { /// Generate a _probably_ unique ID with `size` characters. For readability, /// the characters used are from the sets [0-9], [A-Z], [a-z]. The /// probability of a collision depends on the value of `size`. In /// particular, the probability of a collision is 1/62^(size). pub fn new(size: usize) -> PasteID<'static> { let mut id = String::with_capacity(size); let mut rng = rand::thread_rng(); for _ in 0..size { id.push(BASE62[rng.gen::<usize>() % 62] as char); } PasteID(Cow::Owned(id)) } } impl<'a> fmt::Display for PasteID<'a> { fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result { write!(f, "{}", self.0) } } /// Returns `true` if `id` is a valid paste ID and `false` otherwise. fn valid_id(id: &str) -> bool { id.chars().all(|c| { (c >= 'a' && c <= 'z') || (c >= 'A' && c <= 'Z') || (c >= '0' && c <= '9') }) } /// Returns an instance of `PasteID` if the path segment is a valid ID. /// Otherwise returns the invalid ID as the `Err` value. impl<'a> FromParam<'a> for PasteID<'a> { type Error = &'a str; fn from_param(param: &'a str) -> Result<PasteID<'a>, &'a str> { match valid_id(param) { true => Ok(PasteID(Cow::Borrowed(param))), false => Err(param) } } }