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feat(tvix/store/nixpath): DIGEST_SIZE public, use more consts

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Rename PATH_HASH_SIZE to DIGEST_SIZE.

It's a digest, not hash (we don't necessarily have the internal hash
state anymore), and the fact it's about (Nix)Paths is already visible
from the module name.

Also expose ENCODED_DIGEST_SIZE, so we don't need to do the calculation
inside from_string() method, and it becomes more clear this is a
constant.

Change-Id: I0e7577dd7a6e503039037b986313b214e995d826
Reviewed-on: https://cl.tvl.fyi/c/depot/+/7725
Reviewed-by: tazjin <tazjin@tvl.su>
Reviewed-by: jrhahn <mail.jhahn@gmail.com>
Tested-by: BuildkiteCI
This commit is contained in:
Florian Klink 2023-01-02 12:32:19 +01:00 committed by flokli
parent 2df642231c
commit 8e2b1de3d5
1 changed files with 18 additions and 12 deletions
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30
tvix/store/src/nixpath.rs
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@ -3,7 +3,10 @@ use data_encoding::DecodeError;
use std::fmt; use std::fmt;
use thiserror::Error; use thiserror::Error;
const PATH_HASH_SIZE: usize = 20; 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;
/// Errors that can occur during the validation of name characters. /// Errors that can occur during the validation of name characters.
#[derive(Debug, PartialEq, Eq, Error)] #[derive(Debug, PartialEq, Eq, Error)]
@ -18,39 +21,36 @@ pub enum ParseNixPathError {
#[derive(Debug, PartialEq, Eq)] #[derive(Debug, PartialEq, Eq)]
pub struct NixPath { pub struct NixPath {
pub digest: [u8; PATH_HASH_SIZE], pub digest: [u8; DIGEST_SIZE],
pub name: String, pub name: String,
} }
impl NixPath { impl NixPath {
pub fn from_string(s: &str) -> Result<NixPath, ParseNixPathError> { pub fn from_string(s: &str) -> Result<NixPath, ParseNixPathError> {
let encoded_path_hash_size = NIXBASE32.encode_len(PATH_HASH_SIZE);
let name_offset = encoded_path_hash_size + 1;
// the whole string needs to be at least: // the whole string needs to be at least:
// //
// - 32 characters (encoded hash) // - 32 characters (encoded hash)
// - 1 dash // - 1 dash
// - 1 character for the name // - 1 character for the name
if s.len() < name_offset + 1 { if s.len() < ENCODED_DIGEST_SIZE + 2 {
return Err(ParseNixPathError::InvalidName("".to_string())); return Err(ParseNixPathError::InvalidName("".to_string()));
} }
let digest = match NIXBASE32.decode(s[..encoded_path_hash_size].as_bytes()) { let digest = match NIXBASE32.decode(s[..ENCODED_DIGEST_SIZE].as_bytes()) {
Ok(decoded) => decoded, Ok(decoded) => decoded,
Err(decoder_error) => { Err(decoder_error) => {
return Err(ParseNixPathError::InvalidHashEncoding(decoder_error)) return Err(ParseNixPathError::InvalidHashEncoding(decoder_error))
} }
}; };
if s.as_bytes()[encoded_path_hash_size] != b'-' { if s.as_bytes()[ENCODED_DIGEST_SIZE] != b'-' {
return Err(ParseNixPathError::MissingDash()); return Err(ParseNixPathError::MissingDash());
} }
NixPath::validate_characters(&s[name_offset..])?; NixPath::validate_characters(&s[ENCODED_DIGEST_SIZE + 2..])?;
Ok(NixPath { Ok(NixPath {
name: s[name_offset..].to_string(), name: s[ENCODED_DIGEST_SIZE + 1..].to_string(),
digest: digest.try_into().expect("size is known"), digest: digest.try_into().expect("size is known"),
}) })
} }
@ -88,10 +88,16 @@ impl fmt::Display for NixPath {
#[cfg(test)] #[cfg(test)]
mod tests { mod tests {
use crate::nixpath::PATH_HASH_SIZE; use crate::nixbase32::NIXBASE32;
use crate::nixpath::{DIGEST_SIZE, ENCODED_DIGEST_SIZE};
use super::NixPath; use super::NixPath;
#[test]
fn encoded_digest_size() {
assert_eq!(ENCODED_DIGEST_SIZE, NIXBASE32.encode_len(DIGEST_SIZE));
}
#[test] #[test]
fn happy_path() { fn happy_path() {
let example_nix_path_str = let example_nix_path_str =
@ -99,7 +105,7 @@ mod tests {
let nixpath = let nixpath =
NixPath::from_string(&example_nix_path_str).expect("Error parsing example string"); NixPath::from_string(&example_nix_path_str).expect("Error parsing example string");
let expected_digest: [u8; PATH_HASH_SIZE] = [ let expected_digest: [u8; DIGEST_SIZE] = [
0x8a, 0x12, 0x32, 0x15, 0x22, 0xfd, 0x91, 0xef, 0xbd, 0x60, 0xeb, 0xb2, 0x48, 0x1a, 0x8a, 0x12, 0x32, 0x15, 0x22, 0xfd, 0x91, 0xef, 0xbd, 0x60, 0xeb, 0xb2, 0x48, 0x1a,
0xf8, 0x85, 0x80, 0xf6, 0x16, 0x00, 0xf8, 0x85, 0x80, 0xf6, 0x16, 0x00,
]; ];