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refactor(tvix/nix-compat): move digest decoding into helper function

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This will be used for both Nix hash strings and hash strings without the
algo specified.

Change-Id: Iedfe5494fba5f2be00614ba0fc38bf659eafd447
Reviewed-on: https://cl.tvl.fyi/c/depot/+/8215
Tested-by: BuildkiteCI
Reviewed-by: tazjin <tazjin@tvl.su>
This commit is contained in:
Florian Klink 2023-03-04 01:08:46 +01:00 committed by tazjin
parent daba4cc0e5
commit 4cc4b2a814
1 changed files with 38 additions and 35 deletions
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73
tvix/nix-compat/src/nixhash.rs
View file

@ -75,35 +75,13 @@ pub enum Error {
ConflictingHashAlgos(String, String),
}
/// parses a string to a nix hash.
///
/// strings can be encoded as:
/// - base16 (lowerhex),
/// - nixbase32,
/// - base64 (StdEncoding)
/// - sri string
///
/// The encoding is derived from the length of the string and the hash type.
/// The hash type may be omitted if the hash is expressed in SRI.
/// Even though SRI allows specifying multiple algorithms, Nix does only
/// support a single one.
pub fn from_str(s: &str, algo_str: Option<&str>) -> Result<NixHash, Error> {
// validate algo_str, construct hash_algo
let hash_algo: Option<HashAlgo> = match &algo_str {
Some("sha1") => Some(HashAlgo::Sha1),
Some("sha256") => Some(HashAlgo::Sha256),
Some("sha512") => Some(HashAlgo::Sha512),
Some("md5") => Some(HashAlgo::Md5),
Some(e) => return Err(Error::InvalidAlgo(e.to_string())),
None => None,
};
/// decode a string depending on the hash algo specified externally.
fn decode_digest(s: &str, algo: HashAlgo) -> Result<NixHash, Error> {
// for the chosen hash algo, calculate the expected digest length (as bytes)
let expected_digest_len = hash_algo_length(&algo);
// in case the hash algo is set, try to detect the encoding
if let Some(hash_algo) = hash_algo {
// for the chosen hash algo, calculate the expected digest length (as bytes)
let expected_digest_len = hash_algo_length(&hash_algo);
let decoded_digest = match s.len() {
Ok(NixHash {
digest: match s.len() {
n if n == data_encoding::HEXLOWER.encode_len(expected_digest_len) => {
data_encoding::HEXLOWER
.decode(s.as_ref())
@ -121,9 +99,9 @@ pub fn from_str(s: &str, algo_str: Option<&str>) -> Result<NixHash, Error> {
let nix_hash = from_sri_str(s)?;
// ensure the algo matches what was specified
if hash_algo != nix_hash.algo {
if algo != nix_hash.algo {
return Err(Error::ConflictingHashAlgos(
hash_algo.to_string(),
algo.to_string(),
nix_hash.algo.to_string(),
));
}
@ -131,12 +109,37 @@ pub fn from_str(s: &str, algo_str: Option<&str>) -> Result<NixHash, Error> {
// return
return Ok(nix_hash);
}
}?;
}?,
algo,
})
}
Ok(NixHash {
digest: decoded_digest,
algo: hash_algo,
})
/// parses a string to a nix hash.
///
/// strings can be encoded as:
/// - base16 (lowerhex),
/// - nixbase32,
/// - base64 (StdEncoding)
/// - sri string
///
/// The encoding is derived from the length of the string and the hash type.
/// The hash type may be omitted if the hash is expressed in SRI.
/// Even though SRI allows specifying multiple algorithms, Nix does only
/// support a single one.
pub fn from_str(s: &str, algo_str: Option<&str>) -> Result<NixHash, Error> {
// validate algo_str, construct hash_algo
let algo: Option<HashAlgo> = match &algo_str {
Some("sha1") => Some(HashAlgo::Sha1),
Some("sha256") => Some(HashAlgo::Sha256),
Some("sha512") => Some(HashAlgo::Sha512),
Some("md5") => Some(HashAlgo::Md5),
Some(e) => return Err(Error::InvalidAlgo(e.to_string())),
None => None,
};
// in case the hash algo is set, decode the digest and return
if let Some(algo) = algo {
Ok(decode_digest(s, algo))?
} else {
// try to decode as SRI
let nix_hash = from_sri_str(s)?;