use crate::nixbase32::NIXBASE32; use data_encoding::DecodeError; use std::fmt; use thiserror::Error; pub const DIGEST_SIZE: usize = 20; // lazy_static doesn't allow us to call NIXBASE32.encode_len(), so we ran it // manually and have an assert in the tests. pub const ENCODED_DIGEST_SIZE: usize = 32; // The store dir prefix, without trailing slash. // That's usually where the Nix store is mounted at. pub const STORE_DIR: &str = "/nix/store"; pub const STORE_DIR_WITH_SLASH: &str = "/nix/store/"; /// Errors that can occur during the validation of name characters. #[derive(Debug, PartialEq, Eq, Error)] pub enum ParseNixPathError { #[error("Dash is missing")] MissingDash(), #[error("Hash encoding is invalid {0}")] InvalidHashEncoding(DecodeError), #[error("Invalid name {0}")] InvalidName(String), #[error("Tried to parse an absolute path which was missing the store dir prefix.")] MissingStoreDir(), } #[derive(Debug, PartialEq, Eq)] pub struct NixPath { pub digest: [u8; DIGEST_SIZE], pub name: String, } impl NixPath { pub fn from_string(s: &str) -> Result { // the whole string needs to be at least: // // - 32 characters (encoded hash) // - 1 dash // - 1 character for the name if s.len() < ENCODED_DIGEST_SIZE + 2 { return Err(ParseNixPathError::InvalidName("".to_string())); } let digest = match NIXBASE32.decode(s[..ENCODED_DIGEST_SIZE].as_bytes()) { Ok(decoded) => decoded, Err(decoder_error) => { return Err(ParseNixPathError::InvalidHashEncoding(decoder_error)) } }; if s.as_bytes()[ENCODED_DIGEST_SIZE] != b'-' { return Err(ParseNixPathError::MissingDash()); } NixPath::validate_characters(&s[ENCODED_DIGEST_SIZE + 2..])?; Ok(NixPath { name: s[ENCODED_DIGEST_SIZE + 1..].to_string(), digest: digest.try_into().expect("size is known"), }) } /// Construct a NixPath from an absolute store path string. /// That is a string starting with the store prefix (/nix/store) pub fn from_absolute_path(s: &str) -> Result { match s.strip_prefix(STORE_DIR_WITH_SLASH) { Some(s_stripped) => Self::from_string(s_stripped), None => Err(ParseNixPathError::MissingStoreDir()), } } // Converts the NixPath to an absolute store path string. /// That is a string starting with the store prefix (/nix/store) pub fn to_absolute_path(&self) -> String { format!("{}/{}", STORE_DIR, self) } fn validate_characters(s: &str) -> Result<(), ParseNixPathError> { for c in s.chars() { if c.is_ascii_alphanumeric() || c == '-' || c == '_' || c == '.' || c == '+' || c == '?' || c == '=' { continue; } return Err(ParseNixPathError::InvalidName(s.to_string())); } Ok(()) } } impl fmt::Display for NixPath { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { write!( f, "{}-{}", crate::nixbase32::NIXBASE32.encode(&self.digest), self.name ) } } #[cfg(test)] mod tests { use crate::nixbase32::NIXBASE32; use crate::nixpath::{DIGEST_SIZE, ENCODED_DIGEST_SIZE}; use super::{NixPath, ParseNixPathError}; #[test] fn encoded_digest_size() { assert_eq!(ENCODED_DIGEST_SIZE, NIXBASE32.encode_len(DIGEST_SIZE)); } #[test] fn happy_path() { let example_nix_path_str = "00bgd045z0d4icpbc2yyz4gx48ak44la-net-tools-1.60_p20170221182432"; let nixpath = NixPath::from_string(&example_nix_path_str).expect("Error parsing example string"); let expected_digest: [u8; DIGEST_SIZE] = [ 0x8a, 0x12, 0x32, 0x15, 0x22, 0xfd, 0x91, 0xef, 0xbd, 0x60, 0xeb, 0xb2, 0x48, 0x1a, 0xf8, 0x85, 0x80, 0xf6, 0x16, 0x00, ]; assert_eq!("net-tools-1.60_p20170221182432", nixpath.name); assert_eq!(nixpath.digest, expected_digest); assert_eq!(example_nix_path_str, nixpath.to_string()) } #[test] fn invalid_hash_length() { NixPath::from_string("00bgd045z0d4icpbc2yy-net-tools-1.60_p20170221182432") .expect_err("No error raised."); } #[test] fn invalid_encoding_hash() { NixPath::from_string("00bgd045z0d4icpbc2yyz4gx48aku4la-net-tools-1.60_p20170221182432") .expect_err("No error raised."); } #[test] fn more_than_just_the_bare_nix_store_path() { NixPath::from_string( "00bgd045z0d4icpbc2yyz4gx48aku4la-net-tools-1.60_p20170221182432/bin/arp", ) .expect_err("No error raised."); } #[test] fn no_dash_between_hash_and_name() { NixPath::from_string("00bgd045z0d4icpbc2yyz4gx48ak44lanet-tools-1.60_p20170221182432") .expect_err("No error raised."); } #[test] fn absolute_path() { let example_nix_path_str = "00bgd045z0d4icpbc2yyz4gx48ak44la-net-tools-1.60_p20170221182432"; let nixpath_expected = NixPath::from_string(&example_nix_path_str).expect("must parse"); let nixpath_actual = NixPath::from_absolute_path( "/nix/store/00bgd045z0d4icpbc2yyz4gx48ak44la-net-tools-1.60_p20170221182432", ) .expect("must parse"); assert_eq!(nixpath_expected, nixpath_actual); assert_eq!( "/nix/store/00bgd045z0d4icpbc2yyz4gx48ak44la-net-tools-1.60_p20170221182432", nixpath_actual.to_absolute_path(), ); } #[test] fn absolute_path_missing_prefix() { assert_eq!( ParseNixPathError::MissingStoreDir(), NixPath::from_absolute_path("foobar-123").expect_err("must fail") ); } }