Crate path_dedot

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Expand description

Path Dedot

This is a library for extending Path and PathBuf in order to parse the path which contains dots.

Please read the following examples to know the parsing rules.

Examples

If a path starts with a single dot, the dot means your program’s current working directory (CWD).

use std::path::Path;
use std::env;

use path_dedot::*;

let p = Path::new("./path/to/123/456");
assert_eq!(Path::join(env::current_dir().unwrap().as_path(), Path::new("path/to/123/456")).to_str().unwrap(), p.parse_dot().unwrap().to_str().unwrap());

If a path starts with a pair of dots, the dots means the parent of the CWD. If the CWD is root, the parent is still root.

use std::path::Path;
use std::env;

use path_dedot::*;

let p = Path::new("../path/to/123/456");

let cwd = env::current_dir().unwrap();

let cwd_parent = cwd.parent();

match cwd_parent {
   Some(cwd_parent) => {
      assert_eq!(Path::join(&cwd_parent, Path::new("path/to/123/456")).to_str().unwrap(), p.parse_dot().unwrap().to_str().unwrap());
   }
   None => {
      assert_eq!(Path::join(Path::new("/"), Path::new("path/to/123/456")).to_str().unwrap(), p.parse_dot().unwrap().to_str().unwrap());
   }
}

In addition to starting with, the Single Dot and Double Dots can also be placed to other positions. Single Dot means noting and will be ignored. Double Dots means the parent.

use std::path::Path;

use path_dedot::*;

let p = Path::new("/path/to/../123/456/./777");

assert_eq!("/path/123/456/777", p.parse_dot().unwrap().to_str().unwrap());
use std::path::Path;

use path_dedot::*;

let p = Path::new("/path/to/../123/456/./777/..");

assert_eq!("/path/123/456", p.parse_dot().unwrap().to_str().unwrap());

You should notice that parse_dot method does not aim to get an absolute path. A path which does not start with a MAIN_SEPARATOR, Single Dot and Double Dots, will not have each of them after the parse_dot method is used.

use std::path::Path;

use path_dedot::*;

let p = Path::new("path/to/../123/456/./777/..");

assert_eq!("path/123/456", p.parse_dot().unwrap().to_str().unwrap());

Double Dots which is not placed at the start cannot get the parent beyond the original path. Why not? With this constraint, you can insert an absolute path to the start as a virtual root in order to protect your file system from being exposed.

use std::path::Path;

use path_dedot::*;

let p = Path::new("path/to/../../../../123/456/./777/..");

assert_eq!("123/456", p.parse_dot().unwrap().to_str().unwrap());
use std::path::Path;

use path_dedot::*;

let p = Path::new("/path/to/../../../../123/456/./777/..");

assert_eq!("/123/456", p.parse_dot().unwrap().to_str().unwrap());

Starting from a given current working directory

With the parse_dot_from function, you can provide the current working directory that the relative paths should be resolved from.

use std::env;
use std::path::Path;

use path_dedot::*;

let p = Path::new("../path/to/123/456");
let cwd = env::current_dir().unwrap();

println!("{}", p.parse_dot_from(cwd).unwrap().to_str().unwrap());

Caching

By default, the parse_dot method creates a new PathBuf instance of the CWD every time in its operation. The overhead is obvious. Although it allows us to safely change the CWD at runtime by the program itself (e.g. using the std::env::set_current_dir function) or outside controls (e.g. using gdb to call chdir), we don’t need that in most cases.

In order to parse paths with better performance, this crate provides three ways to cache the CWD.

once_cell_cache

Enabling the once_cell_cache feature can let this crate use once_cell to cache the CWD. It’s thread-safe and does not need to modify any code, but once the CWD is cached, it cannot be changed anymore at runtime.

[dependencies.path-dedot]
version = "*"
features = ["once_cell_cache"]

lazy_static_cache

Enabling the lazy_static_cache feature can let this crate use lazy_static to cache the CWD. It’s thread-safe and does not need to modify any code, but once the CWD is cached, it cannot be changed anymore at runtime.

[dependencies.path-dedot]
version = "*"
features = ["lazy_static_cache"]

unsafe_cache

Enabling the unsafe_cache feature can let this crate use a mutable static variable to cache the CWD. It allows the program to change the CWD at runtime by the program itself, but it’s not thread-safe.

You need to use the update_cwd function to initialize the CWD first. The function should also be used to update the CWD after the CWD is changed.

[dependencies.path-dedot]
version = "*"
features = ["unsafe_cache"]

use std::path::Path;

use path_dedot::*;

unsafe {
    update_cwd();
}

let p = Path::new("./path/to/123/456");

println!("{}", p.parse_dot().unwrap().to_str().unwrap());

std::env::set_current_dir("/").unwrap();

unsafe {
    update_cwd();
}

println!("{}", p.parse_dot().unwrap().to_str().unwrap());

Benchmark

No-cache
cargo bench
once_cell_cache
cargo bench --features once_cell_cache
lazy_static_cache
cargo bench --features lazy_static_cache
unsafe_cache
cargo bench --features unsafe_cache

Statics

Traits

  • ParseDot
    Let Path and PathBuf have parse_dot method.