Change relative location for PathBuf - rust

Question

I have a few PathBufs in my Rust application:
let mut dog_path = PathBuf::from("./animals/dog.png");
let mut cow_path = PathBuf::from("./animals/bovine/cow.jpg");
How could I change these PathBufs so that they're being referred to from the ./animals directory?
// an operation on dog_path
// same operation on cow_path
assert_eq!(PathBuf::from("./dog.png"), dog_path);
assert_eq!(PathBuf::from("./bovine/cow.jpg"), cow_path);

Answer 1

I think you want Path::strip_prefix:
let dog_path = PathBuf::from("./animals/dog.png");
let cow_path = PathBuf::from("./animals/bovine/cow.jpg");
let dog_path_rel = dog_path.strip_prefix("./animals").unwrap();
let cow_path_rel = cow_path.strip_prefix("./animals").unwrap();
assert_eq!(Path::new("dog.png"), dog_path_rel);
assert_eq!(Path::new("bovine/cow.jpg"), cow_path_rel);
But that won't include the leading ./. If that's important to you, you can add it manually:
let dog_path_prefixed = Path::new("./").join(dog_path_rel);
let cow_path_prefixed = Path::new("./").join(cow_path_rel);
assert_eq!(PathBuf::from("./dog.png"), dog_path_prefixed);
assert_eq!(PathBuf::from("./bovine/cow.jpg"), cow_path_prefixed);
playground
Note that strip_prefix returns a Result, meaning it could fail if the path doesn't begin with the given prefix. You may want to handle this case instead of unwraping the result (causing your program to exit with a panic), or you may want to use .expect("your message here") instead to provide a meaningful error message.

Answer 2

If you want a general solution you could look at relative-path crate. It looks like it provide the functionality you want.
use std::path::PathBuf;
use relative_path::RelativePath;
fn main() {
let dog_path = PathBuf::from("./animals/dog.png");
let cow_path = PathBuf::from("./animals/bovine/cow.jpg");
let dog_path = RelativePath::from_path(&dog_path).unwrap();
let cow_path = RelativePath::from_path(&cow_path).unwrap();
let animals_dir = RelativePath::new("./animals");
let dog_path = animals_dir.relative(&dog_path).to_path(".");
let cow_path = animals_dir.relative(&cow_path).to_path(".");
assert_eq!(PathBuf::from("./dog.png"), dog_path);
assert_eq!(PathBuf::from("./bovine/cow.jpg"), cow_path);
}
This is a quick draft, but it shows how to do in a generic way what you are trying to accomplish. I think it could be further optimized, but I literally found this crate 10 minutes ago.