path-posix

Fast POSIX-style path join and normalize using / as the only separator.

Mirrors the semantics of Node.js path.posix.join and path.posix.normalize:

• Resolves . and .. segments
• Collapses consecutive / into one
• Preserves a single trailing / when the input has one
• Empty input normalizes to "."
• Backslashes (\) are treated as literal characters, not separators

Usage

use path_posix::{normalize, join};

assert_eq!(normalize("/a/b/../c"), "/a/c");
assert_eq!(normalize("a//b/./c"), "a/b/c");

assert_eq!(join(&["/foo", "bar", "baz/asdf", "quux", ".."]), "/foo/bar/baz/asdf");
assert_eq!(join(&["a", "/b", "c"]), "a/b/c");

Both functions return Cow<str> — zero allocation when the input is already clean (normalize) or when all segments are empty (join).

Performance

normalize

Input	Time
"" (empty)	~1 ns
/ (root)	~2 ns
/a/b/c (fast path, already clean)	~4 ns
/a/b/c/ (fast path, trailing slash)	~5 ns
/usr/local/.../npm-cli.js (fast path, long)	~19 ns
/a/b/../c (dots)	~31 ns
/a/b/c/d/../../e/f/./g/../h (deep dots)	~66 ns
/a/./b/../c//d/./e/../f/g/../../h (mixed)	~77 ns

join

Input	Time
2 segments	~31 ns
2 segments with ..	~31 ns
3 segments	~29 ns
8 segments with ..	~53 ns

Measured on Apple M4 Pro with cargo bench. See benches/ for details.

Credits

• Node.js path.posix — semantics reference and test cases
• sugar_path — needs_normalization fast-path detection, memchr/memrchr scanning techniques, and NormalizeState buffer architecture

License

MIT