Crate path_dedot

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).

extern crate path_dedot;

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.

extern crate path_dedot;

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.

extern crate path_dedot;

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());

extern crate path_dedot;

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.

extern crate path_dedot;

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.

extern crate path_dedot;

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());

extern crate path_dedot;

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());

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 two ways to cache the CWD.

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"]

extern crate path_dedot;

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

lazy_static_cache

cargo bench --features lazy_static_cache

unsafe_cache

cargo bench --features unsafe_cache

Structs

MAIN_SEPARATOR

The main separator for the target OS.

Traits

ParseDot

Let Path and PathBuf have parse_dot method.