diff options
Diffstat (limited to 'tvix/nix-compat/src/nixhash/ca_hash.rs')
| -rw-r--r-- | tvix/nix-compat/src/nixhash/ca_hash.rs | 48 |
1 files changed, 42 insertions, 6 deletions
diff --git a/tvix/nix-compat/src/nixhash/ca_hash.rs b/tvix/nix-compat/src/nixhash/ca_hash.rs index 93ef52cc63ab..0d6c68d7fa7f 100644 --- a/tvix/nix-compat/src/nixhash/ca_hash.rs +++ b/tvix/nix-compat/src/nixhash/ca_hash.rs @@ -10,13 +10,11 @@ use super::algos::SUPPORTED_ALGOS; use super::from_algo_and_digest; /// A Nix CAHash describes a content-addressed hash of a path. -/// Semantically, it can be split into the following components: /// -/// - "content address prefix". Currently, "fixed" and "text" are supported. -/// - "hash mode". Currently, "flat" and "recursive" are supported. -/// - "hash type". The underlying hash function used. -/// Currently, sha1, md5, sha256, sha512. -/// - "digest". The digest itself. +/// The way Nix prints it as a string is a bit confusing, but there's essentially +/// three modes, `Flat`, `Nar` and `Text`. +/// `Flat` and `Nar` support all 4 algos that [NixHash] supports +/// (sha1, md5, sha256, sha512), `Text` only supports sha256. #[derive(Clone, Debug, Eq, PartialEq)] pub enum CAHash { Flat(NixHash), // "fixed flat" @@ -33,6 +31,44 @@ impl CAHash { } } + /// Constructs a [CAHash] from the textual representation, + /// which is one of the three: + /// - `text:sha256:$nixbase32sha256digest` + /// - `fixed:r:$algo:$nixbase32digest` + /// - `fixed:$algo:$nixbase32digest` + /// which is the format that's used in the NARInfo for example. + pub fn from_nix_hex_str(s: &str) -> Option<Self> { + let (tag, s) = s.split_once(':')?; + + match tag { + "text" => { + let digest = s.strip_prefix("sha256:")?; + let digest = nixbase32::decode_fixed(digest).ok()?; + Some(CAHash::Text(digest)) + } + "fixed" => { + if let Some(s) = s.strip_prefix("r:") { + NixHash::from_nix_hex_str(s).map(CAHash::Nar) + } else { + NixHash::from_nix_hex_str(s).map(CAHash::Flat) + } + } + _ => None, + } + } + + /// Formats a [CAHash] in the Nix default hash format, which is the format + /// that's used in NARInfos for example. + pub fn to_nix_nixbase32_string(&self) -> String { + match self { + CAHash::Flat(nh) => format!("fixed:{}", nh.to_nix_nixbase32_string()), + CAHash::Nar(nh) => format!("fixed:r:{}", nh.to_nix_nixbase32_string()), + CAHash::Text(digest) => { + format!("text:sha256:{}", nixbase32::encode(digest)) + } + } + } + /// This takes a serde_json::Map and turns it into this structure. This is necessary to do such /// shenigans because we have external consumers, like the Derivation parser, who would like to /// know whether we have a invalid or a missing NixHashWithMode structure in another structure, |