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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<NixPath, ParseNixPathError> {
// 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<NixPath, ParseNixPathError> {
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")
);
}
}
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